Updated on 2022/05/19

写真a

 
IWASAKI, Kiyotaka
 
Affiliation
Faculty of Science and Engineering, Graduate School of Advanced Science and Engineering
Job title
Professor

Concurrent Post

  • Faculty of Science and Engineering   School of Creative Science and Engineering

  • Affiliated organization   Global Education Center

Research Institute

  • 2020
    -
    2022

    理工学術院総合研究所   兼任研究員

Education

  • 1999.04
    -
    2002.03

    Waseda University   Graduate School of Science and Engineering  

  • 1997.04
    -
    1999.03

    Waseda University   Graduate School, Division of Science and Engineering   Mechanical Engineering  

  • 1993.04
    -
    1997.03

    Waseda University   Faculty of Science and Engineering  

Degree

  • Waseda University   Doctor of Engineering

Research Experience

  • 2018.03
    -
    Now

    Waseda University   Faculty of Science and Engineering

  • 2014.04
    -
    Now

    Waseda University   Faculty of Science and Engineering

  • 2013.04
    -
    2014.03

    Waseda University   Faculty of Science and Engineering

  • 2012.04
    -
    2013.03

    Waseda University   Research Institute for Science and Engineering

  • 2007.04
    -
    2012.03

    Waseda University   Institue for Advanced Study

  • 2007.03
    -
    2012.03

    Present Associate Professor, Waseda Institute for Advanced Study, Waseda University

  • 2007.03
     
     

    Waseda University

  • 2006.04
    -
    2007.02

    Associate Professor,

  • 2004.10
    -
    2007.02

    Research Scientist, Laboratory for Tissue Engineering and Regenerative Medicine (Director: Dr. Charles Vacanti), Brigham and Women’s Hospital, Harvard Medical School

  • 2004.07
    -
    2006.06

    Lecturer, Institute for Biomedical Engineering, ASMeW, Waseda University

  • 2004.04
    -
    2004.06

    Lecturer, Graduate School of Science and Engineering, Waseda University

  • 2001.04
    -
    2004.03

    Research Associate, Department of Mechanical Engineering, Waseda University

  • 2001
    -
    2004

    Research Associate, Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University

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Professional Memberships

  •  
     
     

    American Heart Association

  •  
     
     

    日本生体医工学会

  •  
     
     

    日本バイオマテリアル学会

  •  
     
     

    日本再生医療学会

  •  
     
     

    日本循環制御学会

  •  
     
     

    TCTAP

  •  
     
     

    日本循環器学会

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    日本人工臓器学会

  •  
     
     

    日本機械学会

  •  
     
     

    日本機械学会バイオエンジニアリング部門

  •  
     
     

    日本バイオレオロジー学会

  •  
     
     

    ライフサポート学会

  •  
     
     

    医療機器臨床試験研究会

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Research Areas

  • Biomaterials

  • Biomedical engineering

Research Interests

  • Cardiovascular Biomedical Engineering, Tissue Engineering, Regulatory Science, Non-clinical testing methodology for Medical Device

Research Seeds

Papers

  • Time-series biological responses toward decellularized bovine tendon graft and autograft for 52 consecutive weeks after rat anterior cruciate ligament reconstruction

    Masafumi Itoh, Hiroki Imasu, Kazuya Takano, Mitsuo Umezu, Ken Okazaki, Kiyotaka Iwasaki

    Scientific Reports   12 ( 1 )  2022.12  [Refereed]

    Authorship:Last author

     View Summary

    Abstract

    There is an essential demand for developing biocompatible grafts for knee anterior cruciate ligament reconstruction (ACLR). This study investigated cell infiltration into decellularized bovine tendon xenografts using a rat knee ACLR model. Twelve-week-old Sprague–Dawley rats were used. At weeks 1, 2, 4, 8, 16, 26, and 52 (each period, n = 6) after ACLR, rats receiving decellularized bovine tendon (group D, n = 42) or autologous tendon (group A, n = 42) as grafts underwent peritibial bone tunnel bone mineral density (BMD), histological, and immunohistological assessments. BMD increased over time in both the groups until week 16 and then remained unchanged without exhibiting significant differences between the groups. Initially, cellularity in group D was lower than that in group A; however, by weeks 4–8, both the groups were comparable to the native anterior cruciate ligament group and cellularity remained unchanged until week 52. Initially, group A had more M1 macrophages, indicating inflammation, whereas group D had more M2 macrophages, indicating tissue regeneration. Nonetheless, the M1 and M2 macrophage counts of both the groups were comparable at most times. This study revealed the excellent recellularization and tendon–bone integration abilities of decellularized tendons using a cross-species model.

    DOI

  • Characteristics of anatomical difficulty for cryoballoon ablation: insights from CT

    T. Hayashi, M. Murakami, S. Saito, K. Iwasaki

    Open Heart   9   e001724  2022

    Authorship:Last author

    DOI

  • Perfusable vascular tree like construction in 3D cell-dense tissues using artificial vascular bed

    Y. Tobe, J. Homma, K. Sakaguchi, H. Sekine, K. Iwasaki, T. Shimizu

    Microvascular Research   141   104321  2022

    DOI

  • Latest outcomes of transcatheter left atrial appendage closure devices and direct oral anticoagulant therapy in patients with atrial fibrillation over the past five years: A systematic review and meta-analysis

    Cardiovascular Intervention and Therapeutics    2022

    Authorship:Last author

    DOI

  • Biodesign program introduction in Japan: promotion of entrepreneurship and viewpoints of education on medical technology innovation

    K. Nakao, M. Umezu, K. Iwasaki

    Journal of Artificial Organs    2022

    Authorship:Last author

    DOI

  • The stability of flow velocity and intracoronary resistance in the intracoronary electrocardiogram-triggered pressure ratio

    Masafumi Nakayama, Nobuhiro Tanaka, Takashi Uchiyama, Takaaki Ohkawauchi, Yusuke Tsuboko, Kiyotaka Iwasaki, Yoshiaki Kawase, Hitoshi Matsuo

    Scientific Reports   11 ( 1 )  2021.12

     View Summary

    <title>Abstract</title>Assessment of coronary artery lesions using the fractional flow reserve and instantaneous flow reserve (iFR) measurements has been found to reduce the incidence of further cardiovascular events. Here, we investigated differences in terms of coronary flow velocity and resistance within the analysis interval between the iFR and the intracoronary electrocardiogram (IC-ECG)-triggered distal/aortic pressure (Pd/Pa) ratio (ICE-T). We enrolled 23 consecutive patients (n = 33 stenoses) who required coronary flow measurements. ICE-T was defined as the average Pd/Pa ratio in the period corresponding to the isoelectric line of the IC-ECG. We compared the index value, flow velocity, and intracoronary resistance during the analysis intervals of the iFR and the ICE-T, both at rest and under hyperemia. ICE-T values and ICE-T intracoronary resistance were both found to be significantly lower, whereas flow velocity was significantly higher than those of the iFR at both rest and under hyperemia (P &lt; 0.001), and all fluctuations in ICE-T values were also significantly smaller than those in the iFR. In conclusion, the ICE-T appears theoretically superior to pressure-dependent indices for analyzing phases with low and stable resistance, without an increase in invasiveness.

    DOI

  • The efficacy of sinus plication in aortic valvuloplasty for bicuspid aortic valve: experiments in a pulsatile flow simulation model.

    Satoshi Arimura, Jumpei Takada, Gohki Nishimura, Natsuki Nakama, Eita Kawasaki, Minoru Matsuhama, Kiyotaka Iwasaki, Hitoshi Kasegawa, Takashi Kunihara

    European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery    2021.03  [International journal]

     View Summary

    OBJECTIVES: Sinus plication has emerged as a promising tool that can lead to better stability in bicuspid aortic valve (BAV) repair. However, the mechanisms underlying the efficacy of this technique are unclear. We evaluated the hydrodynamic effect of sinus plication using the experimental pulsatile flow simulator and our original BAV model in vitro. METHODS: Based on the computed tomography data of a BAV patient who had undergone aortic valvuloplasty, a BAV model (group C, n = 6) was developed with bovine pericardium and vascular prosthesis (J-graft Shield Neo Valsalva 24 mm). We performed sinus plication (group SP, n = 6) in the BAV model and compared hydrodynamic data with the control model in the pulsatile flow simulator. Non-fused cusp angle, annulus diameter and effective height were measured by ultrasonography. RESULTS: The average flow was significantly increased in group SP compared to group C (4.24 ± 0.14 l/min vs 4.14 ± 0.15 l/min, respectively, P = 0.034). The mean transvalvular pressure gradient and regurgitant fraction were significantly decreased in group SP compared to group C (11.6 ± 4.3 mmHg vs 16.6 ± 5.0 mmHg, respectively, P = 0.009 and 14.1 ± 2.0% vs 17.4 ± 2.1%, respectively, P = 0.001). Ultrasound measurement indicated that non-fused cusp angle was significantly increased in group SP compared to group C (163.8° ± 9.2° vs 153.0° ± 4.6°, respectively, P = 0.012). CONCLUSIONS: Sinus plication in the BAV model significantly increased the commissural angle. It was effective in not only controlling regurgitation but also improving valve opening. These finding should be confirmed by evaluating cusp stress and/or long-term durability in the future studies.

    DOI PubMed

  • Comparison of supportive regulatory measures for pediatric medical device development in Japan and the United States.

    Sara Takahashi, Kiyotaka Iwasaki, Haruki Shirato, Mami Ho, Mitsuo Umezu

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs   24 ( 1 ) 90 - 101  2021.03  [Domestic journal]

     View Summary

    Further development of medical devices for children is required in Japan, but the development of such devices is delayed compared to that of medical devices for adults. Herein, we investigated policies for advancing the development of pediatric medical devices in Japan and the United States. Considering the achievements of each policy, we proposed a strategy to promote further development of pediatric medical devices in Japan. We investigated policies for supporting the development of pediatric medical devices and approved cases in Japan and the United States by searching contents of websites of regulatory bodies and other related administrations, and scientific papers. We found the main six policies in Japan and nine main policies in the United States for the development of pediatric medical devices. In the United States, various measures have initiated mainly in the 2000s, while in Japan, the main measures have been in place since 2013. Similarities were found in both countries, such as subsidies for application fees and research and development expenses, exemption of requirements for regulatory approval, and priority review and consultation by the regulatory body. Our study revealed that there are similarities in initiatives by both countries. To promote further development of pediatric medical devices in the future, improvements to expediting the review process to approval by the regulatory body, global development, and implementation of alternative measures to ensure the efficacy and safety of the device instead of large-scale clinical trials should be anticipated through cooperation among industry, government, and academia.

    DOI PubMed

  • Comparative performance analysis of interventional devices for the treatment of ischemic disease in below-the-knee lesions: a systematic review and meta-analysis.

    Emi Kearon Matsuoka, Terumitsu Hasebe, Ryota Ishii, Naoki Miyazaki, Kenzo Soejima, Kiyotaka Iwasaki

    Cardiovascular intervention and therapeutics    2021.02  [Domestic journal]

    Authorship:Last author

     View Summary

    This meta-analysis aimed to evaluate the device performance of conventional balloon catheters (POBA), drug-coated balloons (DCB), bare-metal stents (BMS), and drug-eluting stents (DES) in below-the-knee (BTK) ischemic lesions with regard to lesion characteristics. Online searches of PubMed, Web of Science, and Cochrane databases (2010-2019) were conducted for each of the test devices. Primary patency rates (pp) and major amputation rates 1 year after the use of each device were analyzed using a random-effects meta-analysis model. Meta-regression analysis was conducted to test associations between the outcomes and lesion characteristics. The analysis included 18 studies reporting on 24 separate cohorts comprising 2,438 patients. DES demonstrated the best pp among the test devices (83.6%; 95% confidence interval = 78.4-88.8%, studies = 8; I2 = 66%, P = 0.005). A negative coefficient between lesion length and pp (P = 0.002) was obtained. The ratio of critical limb ischemia (CLI) patients impacted the amputation rates (P = 0.031), whereas no statistically significant difference was found between the devices. DES showed favorable pp in BTK lesions; however, as the lesion lengths using DES were short, pp in long lesions still needs to be evaluated. Shorter lesions gained better pp. A higher ratio of CLI patients resulted in increased amputation rates.

    DOI PubMed

  • Aortic root geometry following valve-sparing root replacement with reimplantation or remodeling: experimental investigation under static continuous pressure.

    Kenichi Sasaki, Takashi Kunihara, Hitoshi Kasegawa, Masahiro Seki, Hiroshi Seki, Jumpei Takada, Saeko Sasuga, Ryo Kumazawa, Mitsuo Umezu, Kiyotaka Iwasaki

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs    2021.01  [Domestic journal]

    Authorship:Last author

     View Summary

    The differences in aortic root geometry associated with various valve-sparing root replacement (VSRR) techniques have not fully been understood. We evaluated the root configuration of current VSRR techniques by developing in vitro test apparatus. Six fresh porcine hearts were used for each model. The aortic root remodeling control group involved replacement of the ascending aorta with diameter reduction of sino-tubular junction (STJ) (C1). The aortic valve reimplantation control group involved replacement of the ascending aorta alone (C2). VSRR included remodeling without (RM) or with annuloplasty (RM + A) and reimplantation with a tube (RI) or a handmade neo-Valsalva graft (RI + V). The root geometry of each model in response to closing hydraulic pressures of 80 and 120 mmHg was investigated using echocardiography. Among the VSRR models, RM yielded the largest aorto-ventricular junction (AVJ), which was similar to those in non-VSRR models [mean AVJ diameter (mm) at 80 mmHg; RM = 25.1 ± 1.5, RM + A = 20.9 ± 0.7, RI = 20.7 ± 0.9, RI + V = 20.8 ± 0.4]. RI + V yielded the largest Valsalva size and largest ratio of Valsalva/AVJ, which was similar to the control group [mean Valsalva diameter (mm) at 80 mmHg; RM = 28.4 ± 1.4, RM + A = 25.8 ± 1.3, RI = 23.6 ± 1.0, RI + V = 30.5 ± 0.8, ratio of Valsalva/AVJ at 80 mmHg; RM = 1.14 ± 0.06, RM + A = 1.24 ± 0.06, RI = 1.15 ± 0.06, RI + V = 1.47 ± 0.05]. The STJ diameter at 80 mmHg was numerically smaller with RM + A (22.4 ± 1.2 mm) than with RM (24.8 ± 2.3 mm, p = 0.11). There were no significant differences in AVJ, Valsalva, or STJ distensibility or ellipticity between procedures. Current modifications, including annuloplasty for remodeling or reimplantation in the setting of neo-Valsalva graft, yield near-physiological root geometries.

    DOI PubMed

  • Bicuspid aortic valve morphology and aortic valvular outflow jets: an experimental analysis using an MRI-compatible pulsatile flow circulation system.

    Kaoru Hattori, Natsuki Nakama, Jumpei Takada, Gohki Nishimura, Ryo Moriwaki, Eita Kawasaki, Michinobu Nagao, Yasuhiro Goto, Hiroshi Niinami, Kiyotaka Iwasaki

    Scientific reports   11 ( 1 ) 2066 - 2066  2021.01  [International journal]

    Authorship:Last author

     View Summary

    The characteristics of aortic valvular outflow jet affect aortopathy in the bicuspid aortic valve (BAV). This study aimed to elucidate the effects of BAV morphology on the aortic valvular outflow jets. Morphotype-specific valve-devising apparatuses were developed to create aortic valve models. A magnetic resonance imaging-compatible pulsatile flow circulation system was developed to quantify the outflow jet. The eccentricity and circulation values of the peak systolic jet were compared among tricuspid aortic valve (TAV), three asymmetric BAVs, and two symmetric BAVs. The results showed mean aortic flow and leakage did not differ among the five BAVs (six samples, each). Asymmetric BAVs demonstrated the eccentric outflow jets directed to the aortic wall facing the smaller leaflets. In the asymmetric BAV with the smaller leaflet facing the right-anterior, left-posterior, and left-anterior quadrants of the aorta, the outflow jets exclusively impinged on the outer curvature of the ascending aorta, proximal arch, and the supra-valvular aortic wall, respectively. Symmetric BAVs demonstrated mildly eccentric outflow jets that did not impinge on the aortic wall. The circulation values at peak systole increased in asymmetric BAVs. The bicuspid symmetry and the position of smaller leaflet were determinant factors of the characteristics of aortic valvular outflow jet.

    DOI PubMed

  • Verification of the differences of scoring effect in current scoring balloons

    Y. Kinoshita, K. Iwasaki, T. Suzuki

    Cardiovascular Intervention and Therapeutics    2021

    DOI

  • Reconstruction of a Vascular Bed with Perfusable Blood Vessels Using a Decellularized Porcine Small Intestine for Clinical Application

    Yusuke Tobe, Katsuhisa Sakaguchi, Jun Homma, Kazunori Sano, Eiji Kobayashi, Hidekazu Sekine, Kiyotaka Iwasaki, Tatsuya Shimizu, Mitsuo Umezu

    IFMBE Proceedings     284 - 292  2021

    DOI

  • Diagnostic Performance and Pressure Stability of a Novel Myocardial Ischemic Diagnostic Index - The Intracoronary-Electrocardiogram-Triggered Distal Pressure/Aortic Pressure Ratio.

    Masafumi Nakayama, Takashi Uchiyama, Nobuhiro Tanaka, Takaaki Ohkawauchi, Shunsuke Miwa, Nobuhiro Hijikata, Yuichi Kobori, Hitoshi Matsuo, Kiyotaka Iwasaki

    Circulation reports   2 ( 11 ) 665 - 673  2020.10  [Domestic journal]

    Authorship:Last author

     View Summary

    Background:
    We hypothesized that the intracoronary-electrocardiogram (IC-ECG)-based pressure index would be more stable and precise than the instantaneous flow reserve (iFR). We investigated the usefulness of the IC-ECG-based pressure index for diagnosing myocardial ischemia.
    Methods and Results:
    Thirty-seven consecutive patients with coronary stenosis requiring physiological assessment were enrolled in the study. iFR was measured at rest and under hyperemia in 51 and 40 lesions, respectively. The IC-ECG-triggered distal pressure (Pd)/aortic pressure (Pa) ratio (ICE-T) was defined as the mean Pd/Pa ratio in the period corresponding to the isoelectric line. The ICE-T was significantly lower than the iFR both at rest and during hyperemia (P<0.00001 for both). Fluctuations in the ICE-T pressure parameters (Pd/Pa, Pa, and Pd) were significantly smaller than those of iFR both at rest and during hyperemia. The diagnostic accuracy of predicting a fractional flow reserve (FFR) ≤0.80 of the ICE-T at rest was significantly higher than that of iFR (P=0.008). Receiver operating characteristic curve analyses showed that the ICE-T predicts FFR ≤0.80 more accurately than the iFR (area under curve 0.897 vs. 0.810 for ICE-T and iFR, respectively).
    Conclusions:
    We identified the period in the IC-ECG in which resting Pd/Pa was low and constant. The IC-ECG-based algorithm may improve the accuracy of diagnosing myocardial ischemia, without increasing invasiveness, compared with pressure-dependent indices.

    DOI PubMed

  • Confirmation of maximal hyperemia by the incremental dose of intracoronary papaverine.

    Masafumi Nakayama, Nobuhiro Tanaka, Jun Yamashita, Kiyotaka Iwasaki

    Cardiovascular intervention and therapeutics   35 ( 4 ) 371 - 378  2020.10  [Domestic journal]

    Authorship:Last author

     View Summary

    We investigated the effect of the papaverine dose increment method to confirm maximal hyperemia for fractional flow reserve (FFR) measurements. We evaluated 115 consecutive patients involving 200 lesions. FFR was measured after intracoronary papaverine injection into the left (12 mg) and right (8 mg) coronary arteries as standard doses. Except for 2 patients who had ventricular tachyarrythmia (VTA), we administered a higher papaverine dose (2 mg added to the standard dose). We compared the FFR values after using different papaverine doses. VTA incidence and electrocardiogram parameters were compared according to the papaverine doses used. The QTU interval and corrected QTU were significantly prolonged after using a higher dose compared with a standard dose. VTA occurred in one patient (0.9%) at the higher dose. There was no significant difference with a strong correlation between the FFR values in the 2 doses (r = 0.963, P < 0.001). Maximal hyperemia was achieved in most patients at the standard papaverine dose. However, 19 lesions changed ischemic diagnosis at the higher dose (12 lesions changed from ischemia negative to positive, and 7 lesions changed from positive to negative). Therefore, to confirm the appropriate ischemia diagnosis for borderline FFR values, it may be favorable to perform another FFR measurement at an incremental papaverine dose.

    DOI PubMed

  • Correction to: A Comprehensive Analysis of Postmarket Surveillance Study Orders: Device Characteristics, Study Statuses, Outcomes, and Potential Contributions.

    Chie Iwaishi, Kiyotaka Iwasaki

    Therapeutic innovation & regulatory science   54 ( 5 ) 1256 - 1257  2020.09  [International journal]

    Authorship:Last author

     View Summary

    In the original article Fig. 3 is not displayed correctly. The corrected figure follows.

    DOI PubMed

  • Measuring the Contractile Force of Multilayered Human Cardiac Cell Sheets.

    Katsuhisa Sakaguchi, Hiroaki Takahashi, Yusuke Tobe, Daisuke Sasaki, Katsuhisa Matsuura, Kiyotaka Iwasaki, Tatsuya Shimizu, Mitsuo Umezu

    Tissue engineering. Part C, Methods   26 ( 9 ) 485 - 492  2020.09  [International journal]

     View Summary

    Three-dimensional (3D) cardiac tissue reconstruction using tissue engineering technology is a rapidly growing area of regenerative medicine and drug screening development. However, there remains an urgent need for the development of a method capable of accurately measuring the contractile force of physiologically relevant 3D myocardial tissues to facilitate the prediction of human heart tissue drug sensitivity. To this end, our laboratory has developed a novel drug screening model that measures the contractile force of cardiac cell sheets prepared using temperature-responsive culture dishes. To circumvent the difficulties that commonly arise during the stacking of cardiomyocyte sheets, we established a stacking method using centrifugal force, making it possible to measure 3D myocardial tissue. Human induced pluripotent stem cell-derived cardiomyocytes were seeded in a temperature-responsive culture dish and processed into a sheet. The cardiac cell sheets were multilayered to construct 3D cardiac tissue. Measurement of the contractile force and cross-sectional area of the multilayered 3D cardiac tissue were then obtained and used to determine the relationship between the cross-sectional area of the cardiac tissue and its contractile force. The contractile force of the 1-, 3-, and 5-layer tissues increased linearly in proportion to the cross-sectional area. A result of 6.4 mN/mm2, accounting for one-seventh of the contractile force found in adult tissue, was obtained. However, with 7-layer tissues, there was a sudden drop in the contractile force, possibly because of limited oxygen and nutrient supply. In conclusion, we established a method wherein the thickness of the cell sheets was controlled through layering, thus enabling accurate evaluation of the cardiac contractile function. This method may enable comparisons with living heart tissue while providing information applicable to regenerative medicine and drug screening models.

    DOI PubMed

  • Feasibility and efficacy of the ultrashort side branch dedicated balloon in coronary bifurcation stenting.

    Yoshinobu Murasato, Masaaki Nishihara, Takahiro Mori, Kyohei Meno, Kodai Shibao, Katsuhiko Takenaka, Kiyotaka Iwasaki

    EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology    2020.07  [International journal]

    Authorship:Last author

     View Summary

    AIMS: We sought to investigate the feasibility and efficacy of the Glider balloon (GB), a side branch (SB) dedicated balloon 4-mm in length, in coronary bifurcation stenting. METHODS AND RESULTS: In bifurcation bench models, stent configuration was examined with micro-focus computed tomography after crossover stenting followed by GB dilation or kissing balloon inflation (KBI). GB dilation maintained cross-sectional stent area without significant deformation and presented effective jailed strut removal in a high-angled bifurcation model. We performed GB dilatation after main vessel (MV) stenting for 207 lesions in 194 patients, which included left main, true-bifurcation lesion, and two-stent treatment in 42.0%, 45.9%, and 14.0%, respectively. Proximal optimization technique (POT) or POT-like inflation was performed in 82.1%. GB crossing failure, SB stenting due to dissection, and stent deformation requiring correction by KBI or MV dilation occurred in 8.7, 1.4, and 5.8%, respectively. Finally, simple GB dilation without KBI had been completed in 91.8% for SB dilation. At 1-year follow-up, target lesion revascularization, cardiac death, myocardial infarction, and stent thrombosis were found in 7.2%, 2.1%, 2.1%, and 1.0%, respectively. CONCLUSIONS: Simple GB dilation after adequate expansion of proximal MV stent provided acceptable acute and long-term results as an alternative to KBI.

    DOI PubMed

  • Effect of QTU prolongation on hyperemic instantaneous wave-free ratio value: a prospective single-center study.

    Masafumi Nakayama, Takashi Uchiyama, Nobuhiro Hijikata, Yuichi Kobori, Nobuhiro Tanaka, Kiyotaka Iwasaki

    Heart and vessels   35 ( 7 ) 909 - 917  2020.07  [Domestic journal]

    Authorship:Last author

     View Summary

    We hypothesized that in patients with QT prolongation, resistance might not decrease in the wave-free period, because QTU prolongation cannot be detected by instantaneous wave-free ratio (iFR) analysis software. We investigated whether corrected QTU (QTUc) prolongation affects the hyperemic iFR value. Forty-two consecutive patients with intermediate stenosis (≥ 50%) in the left anterior descending coronary artery (LAD) were analyzed. Fractional flow reserve (FFR) and hyperemic iFR were simultaneously and continuously recorded with intravenous adenosine triphosphate (ATP) and papaverine infusions. In 17 patients with stenosis in the proximal LAD, coronary flow was measured. Patients were divided into two groups according to the median absolute deviation of the QTUc by ATP administration/QTUc by papaverine administration. FFR, hyperemic iFR, and flow data were compared between each stimulus and group. Moreover, influences of pressure and electrocardiogram parameters on differences in iFR values under ATP and papaverine administration were compared between the following two groups (group 1: the absolute difference of hyperemic iFR values between ATP and papaverine administration is ≤ 0.05; group 2: that is > 0.05). The paired t test and t test were used in analysis. Hyperemic iFR values of patients under the use of papaverine were lower than those of patients under the use of ATP when QTUc was more prolonged by papaverine administration than by ATP administration (ATP 0.74 ± 0.14, papaverine 0.71 ± 0.15, P = 0.025). No significant differences were observed in the FFR value and flow data between the groups. Regarding QTU, QTUc, and QTUc by ATP/QTUc by papaverine, significant differences were observed between group 1 and group 2. Pressure parameters did not induce significant differences. QTUc prolongation induced by papaverine was associated with lower hyperemic iFR values. An iFR-based assessment might lead to inappropriate treatment of patients with QTUc prolongation.

    DOI PubMed

  • A Comprehensive Analysis of Postmarket Surveillance Study Orders: Device Characteristics, Study Statuses, Outcomes, and Potential Contributions.

    Chie Iwaishi, Kiyotaka Iwasaki

    Therapeutic innovation & regulatory science   54 ( 4 ) 953 - 963  2020.07  [International journal]

    Authorship:Last author

     View Summary

    BACKGROUND: The postmarket surveillance system plays a vital role in managing residual risks and identifying safety signals in real-world clinical practice. The Food and Drug Administration (FDA) can order postmarket surveillance studies when safety concerns are raised. We conducted a thorough investigation of device characteristics, study statuses, and the outcomes of US postmarket surveillance studies. METHODS: As of April 2017, we identified 338 orders, corresponding to 394 studies using the FDA database. Additional searches were conducted to identify safety issues or reasons for orders. RESULTS: Completed and active studies were limited. Fifteen of the 394 (3.8%) studies have been completed, and one study resulted in a recommendation of a labeling change. Forty-one (10.4%) studies were active. The majority of the studies (84.3%) were inactive. Three hundred fourteen (93%) orders were issued for implantable devices. The devices for use in women accounted for 144 (43%) orders. The mean from the first premarket approval or 510(k) clearance to 522 orders were 2968 days (n = 9) and 3320 days (n = 326), respectively, and the longest lag was 13,186 days. CONCLUSIONS: Our investigation highlighted that postmarket surveillance study orders resulted in the weeding out of many of the subject medical devices. There were little clinical data produced under the program. Timely and transparent feedback from the postmarket studies are critical for informed decisions by patients and medical practitioners and in expediting patient access to innovative or advanced medical devices.

    DOI PubMed

  • Classification of Aortic Stenosis Using ECG by Deep Learning and its Analysis Using Grad-CAM.

    Erika Hata, Chanjin Seo, Masafumi Nakayama, Kiyotaka Iwasaki, Takaaki Ohkawauchi, Jun Ohya

    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference   2020   1548 - 1551  2020.07  [International journal]

     View Summary

    This paper proposes an automatic method for classifying Aortic valvular stenosis (AS) using ECG (Electrocardiogram) images by the deep learning whose training ECG images are annotated by the diagnoses given by the medical doctor who observes the echocardiograms. Besides, it explores the relationship between the trained deep learning network and its determinations, using the Grad-CAM.In this study, one-beat ECG images for 12-leads and 4-leads are generated from ECG's and train CNN's (Convolutional neural network). By applying the Grad-CAM to the trained CNN's, feature areas are detected in the early time range of the one-beat ECG image. Also, by limiting the time range of the ECG image to that of the feature area, the CNN for the 4-lead achieves the best classification performance, which is close to expert medical doctors' diagnoses.Clinical Relevance-This paper achieves as high AS classification performance as medical doctors' diagnoses based on echocardiograms by proposing an automatic method for detecting AS only using ECG.

    DOI PubMed

  • Finite Element Analysis of the Cutting Balloon With an Adequate Balloon-to-Artery Ratio for Fracturing Calcification While Preventing Perforation.

    Xiaodong Zhu, Mitsuo Umezu, Kiyotaka Iwasaki

    Circulation reports   3 ( 1 ) 1 - 8  2020  [Domestic journal]

    Authorship:Last author

     View Summary

    Background:
    The appropriate balloon-to-artery ratio (BAR) for cutting balloons (CBs), to expand calcified lesions without increasing the risk of coronary artery perforation is unknown. This study investigated the effects of BAR on stress levels in the calcification and at the borders of the coronary artery adjacent to the calcification to determine an appropriate BAR.
    Methods and Results:
    A custom-designed folding process of the CB model was developed. The CB models were deployed in a coronary artery model with a reference diameter of 3.0 mm, length of 24 mm, and wall thickness of 0.8 mm equipped with a 50% diameter stenotic, 360° concentric, 400-µm, and 5-mm-long calcification. Finite element analysis of the expansion of CBs with diameters increasing from 2.0 to 3.0 mm in 0.25-mm increments, corresponding to BARs from 0.67 : 1 to 1 : 1, was conducted with pressures up to 12 atm. Decreasing the CB by 0.25 and 0.5 mm (relative to the reference diameter of 3 mm) preserved maximum principal tensile stress levels comparable to that of a CB with a BAR of 1 : 1 while distinctly reducing the stress at the border of the artery adjacent and calcification.
    Conclusions:
    Selecting a CB that is 0.25 or 0.5 mm lower than the 3-mm reference diameter may be the first choice to effectively fracture calcifications without increasing the risk of severe artery dissection and perforation.

    DOI PubMed

  • Intracoronary Electrocardiogram - Identification of the Culprit Artery in Asymptomatic Myocardial Infarction.

    Masafumi Nakayama, Kiyotaka Iwasaki, Mikio Yuhara, Takayuki Morishima, Yuichi Kobori, Takashi Uchiyama

    Circulation reports   1 ( 8 ) 352 - 353  2019.08  [Domestic journal]

    DOI PubMed

  • 経カテーテル大動脈弁における弁葉周辺および冠動脈開口部流れの可視化のための拍動循環シミュレータ開発

    坪子 侑佑, 藍 龍之介, 前原 瑠海, 許 雪童, 岩崎 清隆

    日本バイオレオロジー学会誌(B&R)   33 ( 2 ) 50 - 50  2019.06  [Refereed]

  • Underfilled Balloon-Expandable Transcatheter Aortic Valve Implantation With Ad Hoc Post-Dilation - Pulsatile Flow Simulation Using a Patient-Specific Three-Dimensional Printing Model.

    Masahiro Yamawaki, Kazuto Obama, Saeko Sasuga, Azuma Takahashi, Yoshiaki Ito, Mitsuo Umezu, Kiyotaka Iwasaki

    Circulation journal : official journal of the Japanese Circulation Society   83 ( 2 ) 461 - 470  2019.01  [Domestic journal]

     View Summary

    BACKGROUND: Underfilled transcatheter aortic-valve implantation with ad hoc post-dilation is a therapeutic option for patients with borderline annuli to avoid acute complication. The effects of this technique on valve leaflet behavior, hydrodynamic performances, and paravalvular leakage (PVL) using patient-specific three-dimensional (3D) aortic-valve models were investigated. Methods and Results: A female octogenarian patient was treated with this technique by using a 23-mm Sapien-XT. Patient-specific models were constructed from pre-procedure computed tomography (CT) data. Change in aortic annulus areas during systolic/diastolic phases and post-procedure stent areas were adjusted to those of the patient. The following was performed: (1) -3 cc initial and -2 cc underfilled post-dilation to the scale-down model by adjusting percent oversizing; and (2) -1 cc initial underfilling, nominal volume, and repeat nominal volume post-dilation using the patient-specific model. Underfilling was associated with higher %PVL. Observation using a high-speed camera revealed distorted leaflets after underfilled implantation, with a longer valve-closing time and smaller effective orifice areas, especially in the -3 cc underfilled implantation. Micro-CT analysis revealed that the transcatheter valves shifted to the opposite side of the large annulus calcification after post-dilation and reduced the malapposition there. CONCLUSIONS: Excessive underfilled implantation showed unacceptable acute hemodynamics. Abnormal leaflet motions after underfilled implantation raised concerns about durability. Flow simulations using patient-oriented 3D models could help to investigate hemodynamics, leaflet motions, and the PVL mechanism.

    DOI PubMed

  • In vitro flow and optical coherence tomography comparison of two bailout techniques after failed provisional stenting for bifurcation percutaneous coronary interventions.

    Julien Adjedj, Fabien Picard, Satoshi Mogi, Kiyotaka Iwasaki, Hamid Aoumeur, Omar Alansari, Edem Agudze, William Wijns, Olivier Varenne

    Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions   93 ( 1 ) E8-E16  2019.01  [International journal]

     View Summary

    OBJECTIVES: To evaluate, in vitro, SB stenting techniques after failed provisional stenting. We aimed to compare flows and stent strut apposition of T and protrusion (TAP) versus Reversed String (RS) techniques using a flow simulator, optical coherence tomography (OCT) using silicon bifurcation phantoms with different bifurcation angulations. BACKGROUND: While bifurcation coronary artery stenoses are preferably treated with provisional T-stenting strategy, the preferred bailout two stents technique to treat the side branch remains unclear. METHODS AND RESULTS: Eleven 30°-angle and ten 60°-angle bifurcation phantoms were used. After performing provisional stenting, TAP and RS techniques were compared in six phantoms with 30° and five with 60° angles. Flow measurement was performed using absolute coronary flow and particle image velocimetry techniques. Strut apposition was evaluated using OCT. Flow analyses showed that disturbed flow regions were observed in the vicinity of floating struts protruded into the lumen both regardless of TAP and RS techniques. OCT analysis showed a higher proportion of floating struts protruding into the main branch with TAP compared to RS, respectively (13% vs. 1%; P <0.001) in both angles. CONCLUSIONS: RS reduces the proportion of floating struts protruding into the main branch compared to TAP, at comparable flow rates. Clinical studies are needed to evaluate feasibility and potential clinical benefit of this technique.

    DOI PubMed

  • Sophisticated hydrodynamic simulation of pulmonary circulation for the preclinical examination of right heart circulatory assist device

    Yusuke Tsuboko, Yasuyuki Shiraishi, Akihiro Yamada, Kiyotaka Iwasaki, Mitsuo Umezu, Tomoyuki Yambe

    IFMBE Proceedings   68 ( 3 ) 717 - 720  2019  [Refereed]

     View Summary

    © Springer Nature Singapore Pte Ltd. 2019. To evaluate systemic circulatory support devices such as left ventricular assist system, surgical heart valve prosthesis, and transcatheter aortic valve, various in vitro hydrodynamic tests have been performed. As these devices are being applied to the pulmonary circulatory support in recent years, novel evaluation platform for right heart support is increasingly demanded. This study aims to develop a pulmonary mechanical circulatory simulation system to assess the hydrodynamic performance of newly designed artificial cardiovascular devices. For the construction of the system, we developed the pneumatically-driven polymer right atrial and ventricular models with the pulmonary arterial valve chamber, silicone-made peripheral pulmonary artery model, and a venous reservoir. A woven polyester vascular graft and commercially available mechanical bileaflet valve were installed into the valve chamber. Then, the right ventricular pressure and pulmonary arterial pressure were regulated by the peripheral resistive unit. As a result, we successfully obtained the standard conditions of our mechanical circulatory system to be 28/3 (systolic/diastolic) mmHg of right ventricular pressure, 29/7, mmHg of pulmonary arterial pressure, 6, mmHg of mean right atrial pressure, and 3.0 L/min of pulmonary flow rate. To carry out the sophisticated assessment for the support of the pulmonary surgical and percutaneous treatments, we are preparing the next step with the reproduction of respiratory changes in pulmonary peripheral resistance, and the patient-specific shape vascular model including catheter access vessels. Under the highly simulated both pulmonary anatomical morphology and hemodynamic function conditions, effective preclinical examination of newly designed surgical or percutaneous pulmonary circulatory support devices can be performed.

    DOI

  • 心血管治療の新展開(ステントグラフト・弁膜症) 壁面間距離マッピング法を用いたNajutaステントグラフトと周術期typelaエンドリークの検討

    宿澤 孝太, 藤井 智也, 墨 誠, 大木 隆生, 梅津 光生, 岩崎 清隆

    人工臓器   47 ( 2 ) S - 14  2018.10

  • Three-Dimensional Strain Measurements of a Tubular Elastic Model Using Tomographic Particle Image Velocimetry.

    Azuma Takahashi, Xiaodong Zhu, Yusuke Aoyama, Mitsuo Umezu, Kiyotaka Iwasaki

    Cardiovascular engineering and technology   9 ( 3 ) 395 - 404  2018.09  [Refereed]  [International journal]

     View Summary

    The evaluation of strain induced in a blood vessel owing to contact with a medical device is of significance to examine the causes leading to vascular injury and rupture. The development of a method to assess strain in largely deformed elastic materials is expected. This study's scope was to measure strain in deformed tubular elastic mock vessels using tomographic particle image velocimetry (tomo-PIV), and to show the applicability of this measurement method by comparing the results with data derived from a finite element analysis (FEA). Strain distribution was calculated from the displacement distribution, which in turn was measured by tracking fluorescent 13 μm particles in a transparent tubular elastic model using tomo-PIV. The von Mises strain distribution was calculated for a model whose inner diameter was subjected to a pressure load, because of which it expanded from 25 to 27.5 mm, adjusting to the diameter change of a human aorta during heartbeat. An FEA simulating the experiment was also conducted. Three-dimensional strain was successfully measured by using the tomo-PIV method. The radial strain distribution in the model linearly decreased outward (from the its inner to its outer side), and the result was consistent with the data obtained from the FEA. The mean von Mises strain measured using tomo-PIV was comparable with that obtained from the FEA (tomo-PIV: 0.155, FEA: 0.156). This study demonstrates the feasibility of utilizing tomo-PIV to quantitatively assess the three-dimensional strain induced in largely deformed elastic models.

    DOI PubMed

  • Low-temperature culturing improves survival rate of tissue-engineered cardiac cell sheets.

    Katsuhisa Sakaguchi, Yuto Hinata, Yuki Kagawa, Kiyotaka Iwasaki, Satoshi Tsuneda, Tatsuya Shimizu, Mitsuo Umezu

    Biochemistry and biophysics reports   14   89 - 97  2018.07  [Refereed]  [International journal]

     View Summary

    Assembling three-dimensional (3D) tissues from single cells necessitates the use of various advanced technological methods because higher-density tissues require numerous complex capillary structures to supply sufficient oxygen and nutrients. Accordingly, creating healthy culture conditions to support 3D cardiac tissues requires an appropriate balance between the supplied nutrients and cell metabolism. The objective of this study was to develop a simple and efficient method for low-temperature cultivation (< 37 °C) that decreases cell metabolism for facilitating the buildup of 3D cardiac tissues. We created 3D cardiac tissues using cell sheet technology and analyzed the viability of the cardiac cells in low-temperature environments. To determine a method that would allow thicker 3D tissues to survive, we investigated the cardiac tissue viability under low-temperature culture processes at 20-33.5 °C and compared it with the viability under the standard culture process at 37 °C. Our results indicated that the standard culture process at 37 °C was unable to support higher-density myocardial tissue; however, low-temperature culture conditions maintained dense myocardial tissue and prevascularization. To investigate the efficiency of transplantation, layered cell sheets produced by the low-temperature culture process were also transplanted under the skin of nude rats. Cardiac tissue cultured at 30 °C developed denser prevascular networks than the tissue cultured at the standard temperature. Our novel findings indicate that the low-temperature process is effective for fabricating 3D tissues from high-functioning cells such as heart cells. This method should make major contributions to future clinical applications and to the field of organ engineering.

    DOI PubMed

  • A proctoring system to manage the learning curve associated with the introduction of transcatheter aortic valve implantation in Japan.

    Masahiro Yamawaki, Kiyotaka Iwasaki, Motoharu Araki, Tsutomu Ito, Yoshiaki Ito, Norio Tada, Kensuke Takagi, Futoshi Yamanaka, Yusuke Watanabe, Masanori Yamamoto, Shinichi Shirai, Kentaro Hayashida

    Heart and vessels   33 ( 6 ) 630 - 639  2018.06  [Refereed]  [Domestic journal]

     View Summary

    As transcatheter aortic valve implantation (TAVI) requires multidisciplinary collaboration, operators and the entire heart team must overcome a steep learning curve. A web-based screening and traditional on-site proctoring system were developed for the introduction of TAVI in Japan. To assess the learning curve involved with the introduction of TAVI under the supervision of a novel proctoring system. We divided 749 consecutive patients enrolled in the OCEAN-TAVI study between October 2013 and August 2015 into the trans-femoral (TF, n = 608) and transapical (TA, n = 141) approach groups to compare outcomes in patients who underwent TAVI during the early proctoring period (proctoring group) and after the procedures began to be performed independently (independent group). The primary endpoint was the rate of composite events regarding early safety (at 30 days) according to the valve academic research consortium-2 criteria. For TF-TAVI, the logistic EuroSCORE and the rate of peripheral artery disease were significantly lower during the independent period. The rate of device success significantly increased during the independent period (90.5 vs. 81.8%, p = 0.005). The rate of the primary endpoint was significantly reduced during the independent period compared to that during the proctoring period for TA-TAVI (21.3 vs. 37.9%, p = 0.031); however, no difference was observed for TF-TAVI (16.8 vs. 13.1%, p = 0.283). No deaths occurred within 30 days during the proctoring period for TF-TAVI. After adjustment using propensity score matching, the procedure time for TF-TAVI (88 ± 43 vs. 102 ± 36 min, p = 0.004) and the rate of life-threatening bleeding for TA-TAVI (3.6 vs. 25%, p = 0.026) reduced during the independent period compared to the values during the proctoring period. During the introduction of TAVI under the supervision of a new proctoring system in Japan, clinical outcomes and technical aspects improved significantly. There are differences in the steepness of the learning curve between TF-TAVI and TA-TAVI.

    DOI PubMed

  • Investigation of adverse events associated with an off-label use of arterial stents and CE-marked iliac vein stents in the iliac vein: insights into developing a better iliac vein stent.

    Takuya Shida, Mitsuo Umezu, Kiyotaka Iwasaki

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs   21 ( 2 ) 254 - 260  2018.06  [Refereed]  [Domestic journal]

     View Summary

    We analyzed the adverse events associated with an off-label use of arterial stents and CE-marked iliac vein stents for the treatment of iliac venous thromboembolism and investigated their relationships with the anatomical features of the iliac vein, to gain insights into the development of a better iliac vein stent. Reports of adverse events following the use of stents in the iliac vein were retrieved from the Manufacturer and User Facility Device Experience (MAUDE) database that contain suspected device-associated complications reported to the Food and Drug Administration. Data from 2006 to 2016 were investigated. The literature analysis was also conducted using PubMed, Cochrane Library, EMBASE, and Web of Science focusing on English articles published up to 4 October 2016. The analysis of 88 adverse events from the MAUDE database and 182 articles from the literature revealed that a higher number of adverse events had been reported following the use of arterial stents in the iliac vein compared to CE-marked iliac vein stents. While stent migration and shortening were reported only for the arterial stents, stent fracture and compression occurred regardless of the stent type, even though a vein does not pulsate. A study of the anatomical features of the iliac vein implies that bending, compression, and kink loads are applied to the iliac vein stents in vivo. For designing, developing, and pre-clinical testing of stents intended for use in the iliac vein, the above mechanical load environments induced by the anatomical features should be considered.

    DOI PubMed

  • Quantitative assessment of paravalvular leakage after transcatheter aortic valve replacement using a patient-specific pulsatile flow model.

    Yutaka Tanaka, Shigeru Saito, Saeko Sasuga, Azuma Takahashi, Yusuke Aoyama, Kazuto Obama, Mitsuo Umezu, Kiyotaka Iwasaki

    International journal of cardiology   258   313 - 320  2018.05  [Refereed]  [International journal]

     View Summary

    BACKGROUND: Quantitative assessment of post-transcatheter aortic valve replacement (TAVR) aortic regurgitation (AR) remains challenging. We developed patient-specific anatomical models with pulsatile flow circuit and investigated factors associated with AR after TAVR. METHODS: Based on pre-procedural computed tomography (CT) data of the six patients who underwent transfemoral TAVR using a 23-mm SAPIEN XT, anatomically and mechanically equivalent aortic valve models were developed. Forward flow and heart rate of each patient in two days after TAVR were duplicated under mean aortic pressure of 80mmHg. Paravalvular leakage (PVL) volume in basal and additional conditions was measured for each model using an electromagnetic flow sensor. Incompletely apposed tract between the transcatheter and aortic valves was examined using a micro-CT. RESULTS: PVL volume in each patient-specific model was consistent with each patient's PVL grade, and was affected by hemodynamic conditions. PVL and total regurgitation volume increased with the mean aortic pressure, whereas closing volume did not change. In contrast, closing volume increased proportionately with heart rate, but PVL did not change. The minimal cross-sectional gap had a positive correlation with the PVL volumes (r=0.89, P=0.02). The gap areas typically occurred in the vicinity of the bulky calcified nodules under the native commissure. CONCLUSIONS: PVL volume, which could be affected by hemodynamic conditions, was significantly associated with the minimal cross-sectional gap area between the aortic annulus and the stent frame. These data may improve our understanding of the mechanism of the occurrence of post-TAVR PVL.

    DOI PubMed

  • Long-Term Durability Test for the Left Ventricular Assist System EVAHEART under the Physiologic Pulsatile Load.

    Kitano T, Iwasaki K

    ASAIO journal (American Society for Artificial Internal Organs : 1992)   64 ( 2 ) 168 - 174  2018.03  [Refereed]

    DOI PubMed

  • Bench testing and coronary artery bifurcations: a consensus document from the European Bifurcation Club.

    John A Ormiston, Ghassan Kassab, Gerard Finet, Yiannis S Chatzizisis, Nicholas Foin, Timothy J Mickley, Claudio Chiastra, Yoshinobu Murasato, Yukata Hikichi, Jolanda J Wentzel, Olivier Darremont, Kiyotaka Iwasaki, Thierry Lefèvre, Yves Louvard, Susann Beier, Hikmat Hojeibane, Ashley Netravali, Jeffery Wooton, Brett Cowan, Mark W Webster, Pau Medrano-Gracia, Goran Stankovic

    EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology   13 ( 15 ) e1794-e1803 - e1803  2018.02  [Refereed]  [International journal]

     View Summary

    This is a consensus document from the European Bifurcation Club concerning bench testing in coronary artery bifurcations. It is intended to provide guidelines for bench assessment of stents and other strategies in coronary bifurcation treatment where the United States Food and Drug Administration (FDA) or International Organization for Standardization (ISO) guidelines are limited or absent. These recommendations provide guidelines rather than a step-by-step manual. We provide data on the anatomy of bifurcations and elastic response of coronary arteries to aid model construction. We discuss testing apparatus, bench testing endpoints and bifurcation nomenclature.

    DOI PubMed

  • Prolonged Inflation Technique Using a Scoring Balloon for Severe Calcified Lesion.

    Yoritaka Otsuka, Taku Koyama, Yuki Imoto, Yoshio Katsuki, Masaaki Kawahara, Keita Nakamura, Sunao Kodama, Hiroo Noguchi, Kiyotaka Iwasaki

    International heart journal   58 ( 6 ) 982 - 987  2017.12  [Refereed]  [Domestic journal]

     View Summary

    Percutaneous coronary intervention for the treatment of a severe calcified lesion is still one of the most technically challenging areas of interventional cardiology. Calcified lesions are a cause of stent underexpansion, which significantly increases the subsequent risks of in-stent restenosis and thrombosis, even when drug-eluting stents are used. In this report, we describe the usefulness of prolonged inflations using a scoring balloon catheter (Scoreflex) for severe calcified lesions. Prolonged inflation using a scoring balloon enables an adequate dilation for treatment of a severe calcified plaque that was unresponsive to conventional technique with or without rotational atherectomy.

    DOI PubMed

  • Investigation of the influence of fluid dynamics on thrombus growth at the interface between a connector and tube.

    Yuki Matsuhashi, Kei Sameshima, Yoshiki Yamamoto, Mitsuo Umezu, Kiyotaka Iwasaki

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs   20 ( 4 ) 293 - 302  2017.12  [Refereed]  [Domestic journal]

     View Summary

    Thrombus formation at the interface between connectors and tubes is a potential risk factor for complications. We investigated time-dependent relationships between formation of thrombus and hemodynamic factors at the interface between connectors and tubes using optical coherence tomography (OCT) under pulsatile flow. A swept-source OCT with the center wavelength of 1330 nm was employed. The sequential process of thrombus formation at the interface of connectors and tubes in the inlet and outlet was investigated. Connectors with and without tapers were tested using identical 50-ml air-contactless circuits. Fresh human blood from healthy volunteers was circulated under pulsatile flow. Thrombus initially formed at the interface between the connector tip and the tube. Geometries of thrombus growth were different between the 2 connectors, and between the inlet and the outlet. Growth of thrombus was observed at the interface between the connectors and tubes over time in 60 min circulation, except at the outlet part of connector without tapers. At the connector without tapers outlet, thrombus propagation length from the connector edge toward the flow downstream was comparable at 10 and 60 min (0.55 ± 0.35 vs. 0.51 ± 0.32 mm, p = 0.83). Analysis using particle image velocimetry showed the presence of a flow reattachment point 1.5 mm downstream from the connector edge. These results suggest that the flow reattachment point inhibits downstream thrombus growth. We quantitatively demonstrated sequential thrombus process at the interface between the connectors and tubes under pulsatile flow of human blood using OCT.

    DOI PubMed

  • 腹部大動脈瘤モデルを用いたステントグラフトの留置形態に関する検討

    赤岡 拓, 宿澤 孝太, 藤井 智也, 伊藤 大輝, 梅津 光生, 大木 隆生, 岩崎 清隆

    日本バイオレオロジー学会誌(B&R)   31 ( 2 ) 125 - 125  2017.05

  • Quantification of Incompletely-apposed Gap after Transcatheter Aortic Valve Replacement Using Patient-specific Models for Understanding the Mechanism of Paravalvular Leak

    Saeko Sasuga, Yutaka Tanaka, Azuma Takahashi, Kazuto Obama, Yusuke Aoyama, Umezu Mitsuo, Shigeru Saito, Kiyotaka Iwasaki

    JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY   69 ( 16 ) S88 - S88  2017.04  [Refereed]

    DOI

  • Analysis of the safety evaluation for premarketing clinical trials of hemodialyzer and of postmarketing safety reports of hemodialyzer in Japan and the US: insights into the construction of a sophisticated premarketing evaluation.

    Masami Saito, Kiyotaka Iwasaki

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs   20 ( 1 ) 62 - 70  2017.03  [Refereed]  [Domestic journal]

     View Summary

    Our aim was to conduct a scoping review of the regulations for hemodialyzers in the safety evaluation in Japan and the United States, and to evaluate the criteria for premarketing clinical trials and postmarketing safety reports to inform the development of a sophisticated premarketing evaluation in Japan. Regulations for approval of hemodialyzers were identified from the databases of the Ministry of Health, Labor and Welfare in Japan and the Federal Drug Agency (FDA) in the United States (US). The criteria for premarket clinical trials and postmarketing safety reports were evaluated for both countries. Standards in Japan required evaluation of blood compatibility and reporting of acute adverse effects by a premarketing clinical trial in 6 of 86 applications with semipermeable membrane materials deemed to be different to those of previously approved devices from 1983 to 31 August 2015. By comparison, the clinical trial was required in one of 545 approvals in the US from 1976 to 29 January 2016, but blood compatibility was not the point. All postmarketing adverse effects identified in Japan were included in the set of 'warnings'. The more stringent requirements for evaluation of blood compatibility and acute adverse effects in Japan seemed to be related to differences in the history of quality management systems for medical devices between the two countries. This study revealed that there were differences between Japan and the US in requiring the premarketing clinical trials for the hemodialyzers. Our findings could be useful for constructing sophisticated premarketing safety evaluation.

    DOI PubMed

  • Reduction in incomplete stent apposition area caused by jailed struts after single stenting at left main bifurcation lesions: micro-CT analysis using a three-dimensional elastic bifurcated coronary artery model.

    Yutaka Hikichi, Mitsuo Umezu, Koichi Node, Kiyotaka Iwasaki

    Cardiovascular intervention and therapeutics   32 ( 1 ) 12 - 17  2017.01  [Refereed]  [Domestic journal]

     View Summary

    Stent struts protruding into ostial side branch called "jailed strut" at bifurcation lesions is a likely cause of thrombus formation. We aimed to investigate the influences of multiple kissing balloon inflation (KBI) for stent expansion, and stent platform design, respectively, on the reduction of incomplete stent apposition area (ISA area) caused by jailed struts at a side-branch ostium, using a three-dimensional elastic left main (LM) bifurcated coronary artery model. The referenced LM bifurcation angle data of 209 patients were stratified by tertiles focusing on the angle between the LM trunk (LMT) and left anterior descending artery (LAD). A bifurcation model was fabricated with angles of 129°, 122.2°, and 76.4° for LMT-LAD, LMT-left circumflex (LCx), and LAD-LCx, respectively, and with diameters of 5, 3.75, and 3.5 mm for LMT, LAD, and LCx, respectively; these diameters fulfill Murray's law. A 75 % stenosis was included along the LMT. One-time and three-time KBIs were conducted using two-link Nobori and three-link Xience Xpedition (n = 6 each). The ISA area was quantified using micro-CT. Three-time KBI was effective in reducing the ISA area compared with one-time KBI for both the Nobori (p = 0.05) and Xience Xpedition (p = 0.07). The ISA area was smaller in the Nobori than in the Xience Xpedition, both in one-time and three-time KBI (one-time KBI: p = 0.003; three-time KBI: p = 0.001). Our findings of this study on reducing the ISA area by focusing on an interventional technique and stent design may help to improve coronary bifurcation intervention for a possibly better long-term clinical outcome.

    DOI PubMed

  • A three-dimensional strain measurement method in elastic transparent materials using tomographic particle image velocimetry.

    Azuma Takahashi, Sara Suzuki, Yusuke Aoyama, Mitsuo Umezu, Kiyotaka Iwasaki

    PloS one   12 ( 9 ) e0184782  2017  [Refereed]  [International journal]

     View Summary

    BACKGROUND: The mechanical interaction between blood vessels and medical devices can induce strains in these vessels. Measuring and understanding these strains is necessary to identify the causes of vascular complications. This study develops a method to measure the three-dimensional (3D) distribution of strain using tomographic particle image velocimetry (Tomo-PIV) and compares the measurement accuracy with the gauge strain in tensile tests. METHODS AND FINDINGS: The test system for measuring 3D strain distribution consists of two cameras, a laser, a universal testing machine, an acrylic chamber with a glycerol water solution for adjusting the refractive index with the silicone, and dumbbell-shaped specimens mixed with fluorescent tracer particles. 3D images of the particles were reconstructed from 2D images using a multiplicative algebraic reconstruction technique (MART) and motion tracking enhancement. Distributions of the 3D displacements were calculated using a digital volume correlation. To evaluate the accuracy of the measurement method in terms of particle density and interrogation voxel size, the gauge strain and one of the two cameras for Tomo-PIV were used as a video-extensometer in the tensile test. The results show that the optimal particle density and interrogation voxel size are 0.014 particles per pixel and 40 × 40 × 40 voxels with a 75% overlap. The maximum measurement error was maintained at less than 2.5% in the 4-mm-wide region of the specimen. CONCLUSIONS: We successfully developed a method to experimentally measure 3D strain distribution in an elastic silicone material using Tomo-PIV and fluorescent particles. To the best of our knowledge, this is the first report that applies Tomo-PIV to investigate 3D strain measurements in elastic materials with large deformation and validates the measurement accuracy.

    DOI PubMed

  • Real-time visualization of thrombus formation at the interface between connectors and tubes in medical devices by using optical coherence tomography.

    Yuki Matsuhashi, Kei Sameshima, Yoshiki Yamamoto, Mitsuo Umezu, Kiyotaka Iwasaki

    PloS one   12 ( 12 ) e0188729  2017  [Refereed]  [International journal]

     View Summary

    BACKGROUND: Blood-contacting devices have contributed to improving the treatment of patients. However, thrombus formation at the interface between a connector and tube is still a potential source of thrombus-related complications that induce stroke or myocardial infarction. We aimed to develop a non-blood-contacting real-time method for visualizing thrombus formation, and to experimentally investigate the time-dependent phenomenon of thrombus formation at the interface between a connector and a tube in a medical device. METHODS AND FINDINGS: An optical coherence tomography device with a center wavelength of 1330 nm was used to visualize thrombus formation during porcine blood circulation for 50 min in a closed 50-mL circulation system isolated from ambient air. The thrombus formation sites at the interface between a tube and connector were visualized. The area of the thrombus formation at the interface between the inlet of the connector and the tube was found to be 0.012 ± 0.011 mm2. Conversely, at the interface between the outlet of the connector and the tube, the area was found to be 0.637 ± 0.306 mm2. Thus, significantly larger amounts of thrombus were formed at the outlet interface (p < 0.01). The thrombus formation area at the outlet interface increased over time. Conversely, the area of thrombus formation showed repeated increasing and decreasing behavior at the inlet interface. Flow visualization with particle image velocimetry showed the presence of a flow separated area in the minimal flow phase at the inlet interface and a large recirculating slow flow region at the outlet interface in the minimal flow phase. These data suggested that the recirculating stagnant flow region contributed to thrombus growth. CONCLUSIONS: The method presented here was effective in quantitatively assessing time-dependent phenomena of thrombus formation at the connector-tube interface. The method may contribute to the assessment of thrombogenicity of a novel design of connector.

    DOI PubMed

  • Analysis of safety measures for medical device software

    Kitawaki Ryota, Umezu Mitsuo, Iwasaki Kiyotaka, Nambu Kyojiro, Kasanuki Hiroshi

    Transactions of Japanese Society for Medical and Biological Engineering   55 ( 3 ) 196 - 196  2017

     View Summary

    <p>Software is widely used in medical device but there are such safety issues that leading causes of medical device recalls in the US lie in software design. The objective of this study is to analyze safety measures for medical device software.</p><p>We identified safety measures for medical device software in Japan, US and Europe (A). We also identified safety measures for software used in various industries from Software Engineering Body of Knowledge (SWEBOK) and Software Quality Body of Knowledge (SQuBOK) (B). We appraised A based on B using a three-point scoring where safety measures in B are adequately (3), for some extent (2), or not at all (1) mentioned in A.</p><p>We identified 28 safety measures, 26 from SWEBOK and 16 from SQuBOK. The average score of the current safety measures was 1.4 for SWEBOK and 1.5 for SQuBOK.</p><p>The scoring results indicate inadequacy of the current safety measures.</p>

    DOI CiNii

  • Six-case reports in clinical trials on a new surgical navigation system for thoracic and thoracoabdominal aortic aneurysm

    Uematsu Miyuki, Aomi Shigeyuki, Yamazaki Kenji, Iwasaki Kiyotaka, Umezu Mitsuo, Nakaoka Ryusuke, Haishima Yuji, Suzuki Takashi, Muragaki Yoshihiro, Iseki Hiroshi

    Transactions of Japanese Society for Medical and Biological Engineering   55 ( 5 ) 434 - 434  2017

     View Summary

    <p>We have been developing a surgical navigation system to support a surgeon to identify the anatomical orientation. Its first prototype was designed in 2004 and clinically tested in 2006. During this decade, we have utilized it in one hundred clinical cases. Learned through trial and error, it was found that this system needed to improve the usability and the reliability in registration process to show valuable information for surgery. Our improved system was approved to use for clinical pre-trial from Hospital Ethics Committee of Tokyo Women's Medical University (160402), and it was utilized for six cases from June 2016 to January 2017. The new system worked suitably compared with the former one. As for spending time on the new system, it took 9.8±1.7 minutes before thoracotomy and 6.4±1.5 minutes after adhesiolysis. Target arteries were determined smoothly in all cases. We hope that widespread use of the system would be promoted.</p>

    DOI CiNii

  • Simulation of Transcatheter Aortic Valve Replacement and Assessment of Regurgitation in in-vitro Pulsatile Model With Patient-specific Anatomy

    Yutaka Tanaka, Yusuke Aoyama, Kazuto Obama, Saeko Sasuga, Azuma Takahashi, Mitsuo Umezu, Shigeru Saito, Kiyotaka Iwasaki

    CIRCULATION   134  2016.11  [Refereed]

  • The effect of tendon stem/progenitor cell (TSC) sheet on the early tendon healing in a rat Achilles tendon injury model.

    Issei Komatsu, James H-C Wang, Kiyotaka Iwasaki, Tatsuya Shimizu, Teruo Okano

    Acta biomaterialia   42   136 - 146  2016.09  [Refereed]  [International journal]

     View Summary

    UNLABELLED: Tissue-engineering approaches have a great potential to improve the treatment of tendon injuries that affect millions of people. The present study tested the hypothesis that introduction of a tendon derived stem/progenitor cell (TSC) sheet accelerates tendon healing and tendon regeneration in a rat model. TSC sheets were produced on temperature-responsive culture dishes. Then, they were grafted on unwounded Achilles tendons and at sites of a 3mm of Achilles tendon defect. At 2 and 4weeks after implantation tendons were examined by histology, immunohistochemistry, transmission electron microscopy (TEM) and mechanical testing. The results showed that the implanted TSC sheet remained stably attached on the tendon surface at 4 weeks after implantation. Moreover, in the tendon defect model, tendon defect area where TSC sheet was implanted was well regenerated and had better organized collagen fibers with elongated spindle shaped cells, compared to relatively disorganized collagen fibers and round shaped cells in the control group. TEM observations revealed longitudinally aligned collagen fibers and thick collagen fibrils in the TSC sheet implanted group. Finally, at 4weeks mechanical property of the TSC sheet implanted tendon had better ultimate load than the control. In conclusion, this study demonstrates the feasibility of implanting TSC sheets on tendons in vivo. Introduction of the cell sheets into a tendon defect significantly improved histological properties and collagen content at both 2 and 4 weeks after implantation, indicating that TSC sheets may effectively promote tendon remodeling in the early stages of tendon healing. STATEMENT OF SIGNIFICANCE: Tendon injury is a highly prevalent clinical problem that debilitates millions of people worldwide in both occupational and athletic settings. It also costs billions of healthcare dollars in treatment every year. In this study, we showed the feasibility of using tendon derived stem cell sheet to deliver biologically active tenogenic-constructs and promote tendon regeneration. This work has the potential to impact the orthopaedic surgery and sports medicine fields in the treatment of tendon injury.

    DOI PubMed

  • Regulatory science of new technology: tendency of medical professionals' interests on silicone breast implants.

    Tomomichi Nakazaki, Koji Ikeda, Kiyotaka Iwasaki, Mitsuo Umezu

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs   19 ( 3 ) 283 - 8  2016.09  [Refereed]  [Domestic journal]

     View Summary

    New technology related to artificial organs is most attractive for worldwide researchers. We believe they must contribute for the future patients against untreatable diseases. Regulatory science is a new science to establish 'social acceptance' of new technology into the clinical market as soon as possible. In the history of silicone breast implants, we could recognize risks many times; however, we missed such chances to prevent a subsequent crisis. We analyzed the trend of published literature related to silicone breast implants to review the medical professionals' interests on such risks. This trend showed, despite issues of a social acceptance of silicone breast implants in a few countries, other countries' medical professionals had no interest. Our hypothesis is 'medical professionals face the government and do not have contributed to re-establish the social acceptance of new technologies for patients'. Any technology does not have the complete evidence of safety, efficacy and quality, despite regulatory authorities' review and approval with clinical evidences. medical professionals need to conduct subsequently the epidemiological study, to take a meta-analysis periodically and to create/update the guidance for their patients under their professional ethics after the marketing of new technologies. We need to take seriously the 'lesson learned' from the history of silicone breast implants for all kind of new technologies existed in the present.

    DOI PubMed

  • Time Series Analysis of the Effectiveness and Safety of Capsule Endoscopy between the Premarketing and Postmarketing Settings: A Meta-Analysis.

    Kazuo Iijima, Mitsuo Umezu, Kiyotaka Iwasaki

    PloS one   11 ( 6 ) e0153662  2016  [Refereed]  [International journal]

     View Summary

    BACKGROUND: Clinical studies for assessing the effectiveness and safety in a premarketing setting are conducted under time and cost constraints. In recent years, postmarketing data analysis has been given more attention. However, to our knowledge, no studies have compared the effectiveness and the safety between the pre- and postmarketing settings. In this study, we aimed to investigate the importance of the postmarketing data analysis using clinical data. METHODS AND FINDINGS: Studies on capsule endoscopy with rich clinical data in both pre- and postmarketing settings were selected for the analysis. For effectiveness, clinical studies published before October 10, 2015 comparing capsule endoscopy and conventional flexible endoscopy measuring the detection ratio of obscure gastrointestinal bleeding were selected (premarketing: 4 studies and postmarketing: 8 studies) from PubMed (MEDLINE), Cochrane Library, EMBASE and Web of Science. Among the 12 studies, 5 were blinded and 7 were non-blinded. A time series meta-analysis was conducted. Effectiveness (odds ratio) decreased in the postmarketing setting (premarketing: 5.19 [95% confidence interval: 3.07-8.76] vs. postmarketing: 1.48 [0.81-2.69]). The change in odds ratio was caused by the increase in the detection ratio with flexible endoscopy as the control group. The efficacy of capsule endoscopy did not change between pre- and postmarketing settings. Heterogeneity (I2) increased in the postmarketing setting because of one study. For safety, in terms of endoscope retention in the body, data from the approval summary and adverse event reports were analyzed. The incidence of retention decreased in the postmarketing setting (premarketing: 0.75% vs postmarketing: 0.095%). The introduction of the new patency capsule for checking the patency of the digestive tract might contribute to the decrease. CONCLUSIONS: Effectiveness and safety could change in the postmarketing setting. Therefore, time series meta-analyses could be useful to continuously monitor the effectiveness of medical device in clinical practices.

    DOI PubMed

  • Newly designed tissue / cell storage bag for cryopreserved homograft by application of CO2 laser welding technique

    N. Motomura, A. Saito, Y. Kurosaki, K. Sato, K. Iwasaki, M. Takanashi, S. Tamura, T. Obase, K. Ueda

    IIR Workshop    2016

  • Biomechanical Modeling to Improve Coronary Artery Bifurcation Stenting: Expert Review Document on Techniques and Clinical Implementation.

    Antonios P Antoniadis, Peter Mortier, Ghassan Kassab, Gabriele Dubini, Nicolas Foin, Yoshinobu Murasato, Andreas A Giannopoulos, Shengxian Tu, Kiyotaka Iwasaki, Yutaka Hikichi, Francesco Migliavacca, Claudio Chiastra, Jolanda J Wentzel, Frank Gijsen, Johan H C Reiber, Peter Barlis, Patrick W Serruys, Deepak L Bhatt, Goran Stankovic, Elazer R Edelman, George D Giannoglou, Yves Louvard, Yiannis S Chatzizisis

    JACC. Cardiovascular interventions   8 ( 10 ) 1281 - 1296  2015.08  [Refereed]  [International journal]

     View Summary

    Treatment of coronary bifurcation lesions remains an ongoing challenge for interventional cardiologists. Stenting of coronary bifurcations carries higher risk for in-stent restenosis, stent thrombosis, and recurrent clinical events. This review summarizes the current evidence regarding application and use of biomechanical modeling in the study of stent properties, local flow dynamics, and outcomes after percutaneous coronary interventions in bifurcation lesions. Biomechanical modeling of bifurcation stenting involves computational simulations and in vitro bench testing using subject-specific arterial geometries obtained from in vivo imaging. Biomechanical modeling has the potential to optimize stenting strategies and stent design, thereby reducing adverse outcomes. Large-scale clinical studies are needed to establish the translation of pre-clinical findings to the clinical arena.

    DOI PubMed

  • Lessons from the real bench: non-BRS.

    John Ormiston, Olivier Darremont, Kiyotaka Iwasaki, Yoshinobu Murasato, Yutaka Hikichi, Bruce Webber, Mark Webster

    EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology   11 Suppl V   V27-30 - V30  2015  [Refereed]  [International journal]

     View Summary

    Bench testing of stents used in bifurcations can provide information on the general properties that influence performance including crossing profile, radial strength, recoil, flexibility and radiopacity. Problems with device delivery can be clarified. Bench testing identified that side branch dilatation caused stent distortion and elucidated correction strategies. Bench testing led to a stent design change adding connectors between hoops to help overcome the clinical problem of longitudinal distortion. Testing on the bench can determine best deployment strategies and showed that a two-step post-dilatation strategy produced the best deployment with "crush" stenting. Scanning electron microscopy showed that withdrawal of a coronary guidewire trapped between a stent (or scaffold) and a mock arterial wall during a provisional side branch stenting strategy caused only mild linear polymer coating damage. Stent fracture can cause adverse clinical events and our repetitive bend test identified the stents most resistant to fracture. Causes of obstruction of the passage of a balloon over a wire through the side of a stent include damage to the catheter tip, complex cell geometry and inadvertent passage of a wire behind a strut. Bench testing plays a major role in validation of computer modelling of bifurcation treatments and flow alterations.

    DOI PubMed

  • Optimal kissing balloon inflation after single-stent deployment in a coronary bifurcation model.

    Yoshinobu Murasato, Kiyotaka Iwasaki, Tadashi Yamamoto, Takanobu Yagi, Yutaka Hikichi, Yasunori Suematsu, Tomohiko Yamamoto

    EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology   10 ( 8 ) 934 - 41  2014.12  [Refereed]  [International journal]

     View Summary

    AIMS: To define the optimal kissing balloon inflation (KBI) after single-stent deployment in a coronary bifurcation model. METHODS AND RESULTS: We deployed stents in main vessels (MV) followed by KBI in various conditions and compared the stent configurations. A) KBI at the operator's discretion vs. under the guidelines of minimal balloon overlapping (MBO). Various stent configurations were observed after the former option, whereas similar maximal dilation points were observed under the MBO guidelines. B) Long balloon overlapping (LBO) vs. MBO with proximal MV dilated by a large balloon. The proximal MV was dilated to an ideal round shape with MBO versus an oval shape with LBO. C) Two-link vs. 3-link stents. Although the 2-link stent was advantageous to open the side branch, it incurred a risk of overdilatation of the proximal struts, whereas the 3-link stent preserved its structure. Computed simulations of coronary flow were analysed in the following left main coronary models: circle with a diameter of 4 and 5.5 mm, ellipse with longitudinal direction and tilt position. They revealed that the overdilated side was exposed to low shear stress regardless of its shape. CONCLUSIONS: Optimal KBI can be achieved with MBO and proximal dilatation by an optimally sized balloon.

    DOI PubMed

  • What are Key Factors to Achieve Better Stent Apposition at Left Main Bifurcation by Culottes Stenting Technique? Micro-CT Analysis Using Bifurcated Elastic Coronary Artery Models

    Yutaka Hikichi, Takafumi Ohba, Tsuyoshi Inukai, Sho Kishigami, Jun Arai, Mitsuo Umezu, Koichi Node, Kiyotaka Iwasaki

    CIRCULATION   130  2014.11  [Refereed]

  • Angulation Range of Coronary Artery During the Cardiac Cycles is a Key Factor Inducing Stent Fracture; Demonstration by an in vitro Accelerated Durability Test

    Kiyotaka Iwasaki, Jun Arai, Takafumi Ohba, Hirotsugu Tokutake, Zhu Xiaodong, Mitsuo Umezu

    CIRCULATION   130  2014.11  [Refereed]

  • Simultaneous comparison of thrombogenic reactions to different combinations of anticoagulants, activated clotting times, and materials.

    Mirei Nagai, Kiyotaka Iwasaki, Mitsuo Umezu, Makoto Ozaki

    Journal of biomedical materials research. Part B, Applied biomaterials   102 ( 8 ) 1605 - 12  2014.11  [Refereed]  [International journal]

     View Summary

    Thrombogenic reactions under multiple interactions of pharmacological agents, doses, and materials have not been well understood yet. The aim of this study was to investigate the ability to simultaneously compare thrombogenic reactions to different combinations of anticoagulants, doses, and blood-contacting materials, in a single human blood using an in vitro test method. Four venous blood samples were drawn from each of six healthy volunteers into syringes that contained two different amounts of heparin and argatroban to set the activated clotting time (ACT) to approximately 200 or 500 s, respectively. The four blood samples from each volunteer were immediately poured into two clinical-grade extracorporeal circulation tubes: a polyvinyl chloride (PVC) tube and a poly(2-methoxyethyl acrylate)-coated (PMEA) PVC tube. These tubes with an inner diameter of 12.7 mm were rotated at 183 rpm in a 37°C chamber for 10 min. The results indicated that the in vitro thrombogenicity test method was capable of assessing differences in platelet factor 4 and β-thromboglobulin increases among different combinations of the two materials, two anticoagulants, and two ACTs. Higher amounts of total plasma proteins were absorbed on PVC tubes than on PMEA-coated tubes when using the same anticoagulant and dose. These data elucidate that the in vitro thrombogenicity test method is useful for the simultaneous quantitative evaluation of the influences of various combinations of materials, pharmacological agents, and doses on thrombogenicity in a single human blood.

    DOI PubMed

  • 医療機器・材料の血液適合性評価と,生体外(in vitro)で可能な評価手法の展望,生体適合性制御と要求特性掌握から実践する高分子バイオマテリアルの設計・開発戦略

    岩崎清隆

    サイエンス&テクノロジー     247 - 258  2014.05

  • Orbital Shaking Promoted Vascular Elastogenesis in Cultured Rat Aortic Smooth Muscle Cells

    Ryosuke Shiraishi, Kiyotaka Iwasaki, Takashi Aida, Shumpei Saito, Nur Khatijah Mohd Zin, Shinji Takeoka, Mitsuo Umezu, Susumu Minamisawa

    BIOPHYSICAL JOURNAL   106 ( 2 ) 615A - 615A  2014.01  [Refereed]

    DOI

  • COMBINED ANALYSIS OF PATHOLOGY AND HEMODYNAMICS OF HUMAN UNRUPTURED CEREBRAL ANEURYSM WITH THIN-WALLED REGION

    Yasutaka Tobe, Takanobu Yagi, Yuki Iwabuchi, Momoko Yamanashi, Kenji Takamura, Kiyotaka Iwasaki, Mitsuo Umezu, Yoshifumi Hayashi, Hirotaka Yoshida, Atsushi Nakajima, Kazutoshi Nishitani, Yoshifumi Okada, Michihito Sugawara, Shin Hiraguchi, Toshiro Kubo, Shigemi Kitahara

    PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2013, PT A    2014  [Refereed]

    DOI

  • Investigation of mechanical load on proximal left anterior descending of coronary artery

    Tadashi Yamamoto, Kiyotaka Iwasaki, Jun Arai, Katsumi Ohori, Mitsuo Umezu

    IFMBE Proceedings   43   805 - 808  2014

     View Summary

    It is clinically recognized that percutaneous coronary intervention (PCI) treatment for proximal left anterior descending (LAD) artery disease is resulting in less satisfactory in comparison with other lesions. However, the reason has not yet clarified. The purpose of this study is to investigate the mechanical loading conditions in proximal LAD artery. This study hypothesized that the coronary artery is prestretched in the heart. In order to investigate the pre-stretched value, porcine heart was obtained from a local slauterhouse. Two points were marked at coronary artery and its distance was measured. Two-dimensional distances (L1) between the dots marked on vessel centerline were measured with digital microscope. The coronary artery was separated from the heart, the distance between the points was measured again (L2). Pre-stretched ratio was calculated as (L1-L2)/L2 ×100%. 101 consecutive patients of coronary CT were taken in Hokkaido Cardiovascular Hospital from September 2012 in order to investigate dynamic loads acting on coronary artery. The distance of proximal LAD artery was measured in diastolic phase (Ld) and systolic phase (Ls) from a stretch view taken from CT. Shortening ratio was defined as (Ld-Ls)/Ld ×100%. The twist angle was defined as a sum of the following two angles and mesured in end-systolic and end-diastolic phase. One is tha angle between the line connecting the centers of LAD and left circumflex (LCX), and the perpendicular line toward abdominal to dorsal. The other is the angle between the line connecting the centers of LAD and the first septal branch, and the perpendicular line. Twisting ratio was calculated as θ/Ld ×100%.Results showed that the pre-stretched ratio was calculated to be 7.6±2.9% (mean±SD) in porcine LAD artery. The length of proximal LAD artery of human coronary artery was 26.6 ± 9.3mm (mean±SD). Shortening ratio was calculated to be 6.1 ± 6.2% (mean±SD). And the mean twisting ratio was calculated to be 0.6 °/mm. This study revealed the pre-stretched value of proximal LAD artery due to restrain from the myocardium. Moreover shortening and twisting motions in proximal LAD artery were quantified.

    DOI

  • Awareness of Electromagnetic Interference in Patients with Cardiac Implantable Electronic Devices: An Analysis of Hospital Explanations and Other Factors. Regulatory Science of Mecical Products(医薬品医療機器レギュラトリーサイエンス)

    F.Aoki, K.Iwasaki, M.Umezu, H.Kasanuki

      4 ( 2 )  2014

  • Application of the International Medical Alarm Standard in Clinical Practice.Pharmaceutical and Medical Device Regulatory Science(医薬品医療機器レギュラトリーサイエンス)

    Masahiro Echigo, Hiroshi Kasanuki, Kiyotaka Iwasaki, Mitsuo Umezu

      45 ( 3 )  2014

  • 冠動脈ステントの3回拡張法と臨床実践での評価

    山本匡, 岩﨑清隆, 新井淳, 北原茂美, 梅津光生

    生体医工学   51 ( 6 ) 350 - 356  2014

    DOI

  • 組織無細胞化技術による再生医療

    岩﨑清隆

    日本機械学会誌   117 ( 1142 ) 28 - 31  2014.01

  • Fracture Potentials and Dynamic Flexibility of Peripheral Stents: Insights into Clinical Practice From Durability Tests Simulating Multi-loading Environments of Superficial Femoral and Popliteal Arteries

    Iwasaki Kiyotaka, Kishigami Sho, Arai Jun, Ohba Takafumi, Tokutake Hirotsugu, Zhu Xiaodong, Yagishita Yuichi, Noguchi Yusuke, Yamamoto Tadashi, Hikichi Yutaka, Umezu Mitsuo

    CIRCULATION   128 ( 22 )  2013.11  [Refereed]

  • 冠動脈ステントの疲労破壊:破損耐久性の可視化

    岩﨑清隆, 梅津光生

    可視化情報学会誌   33 ( 131 ) 139 - 144  2013.10

    DOI

  • Numerical analysis of blood flow distribution in 4- and 3-branch vascular grafts.

    Chikako Konoura, Takanobu Yagi, Masanori Nakamura, Kiyotaka Iwasaki, Yi Qian, Shigeo Okuda, Akihiro Yoshitake, Hideyuki Shimizu, Ryohei Yozu, Mitsuo Umezu

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs   16 ( 2 ) 157 - 63  2013.06  [Refereed]  [Domestic journal]

     View Summary

    Trifurcated arch grafts (3-branch grafts) are now being used to repair the thoracic aorta in addition to conventional arch grafts (4-branch grafts). The anatomical shape of the 3-branch graft is different from the original vessel, so it is necessary for clinical application to evaluate blood flow distribution in the graft to assess whether there is adequate blood flow to the target organs. To achieve this, we developed a computational fluid dynamics (CFD) method to evaluate blood flow distribution in the grafts. Aortic blood flow was measured by phase-contrast magnetic resonance imaging (PC-MRI), and flow distribution into the branched vessels was obtained. The MRI image was used to create a patient-specific image model that represents the geometry of the aortic arch. The CFD analysis method was employed to determine a boundary condition of the blood flow analysis in the aorta using a patient-specific image model. We also created simplified models of 4-branch and 3-branch grafts and used our CFD analysis method to compare blood flow distribution among simplified models. It was found that blood flow distribution in the descending aorta was 71.3 % for the 4-branch graft and 67.7 % for the 3-branch graft, indicating that a sum of branching flow in the 3-branch graft was almost the same as the one in the 4-branch graft. Therefore, there is no major concern about implanting a new 3-branch graft. Our CFD analysis method may be applied to estimate blood flow distribution of a newly developed vascular graft prior to its clinical use and provide useful information for safe use of the graft.

    DOI PubMed

  • Preliminary study on the development of a system dynamics model: the case of EVAHEART.

    Tsugiko Kato, Mitsuo Umezu, Kiyotaka Iwasaki, Hiroshi Kasanuki, Yutaka Takahashi

    Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs   16 ( 2 ) 242 - 7  2013.06  [Refereed]  [Domestic journal]

     View Summary

    The Japanese medical device industry's stagnation over the years can be attributed to the uncertainty related to device development. The purpose of this study is to identify the major factors that impact development. We studied the ventricular assist device EVAHEART through interviews with the persons involved and created a development model using system dynamics. There are at least six stages in the device development process, including interactions with academia and the government. Through a simulation and comparison to Novacor, it was determined that the satisfaction of academia leads to government action in the subsequent measures. Our trial simulation of EVAHEART suggests that it has the potential to clarify unclear relationships in the development of devices.

    DOI PubMed

  • Attitudes toward interprofessional healthcare teams: a comparison between undergraduate students and alumni.

    Takatoshi Makino, Hiromitsu Shinozaki, Kunihiko Hayashi, Bumsuk Lee, Hiroki Matsui, Nana Kururi, Hiroko Kazama, Hatsue Ogawara, Fusae Tozato, Kiyotaka Iwasaki, Yasuyoshi Asakawa, Yumiko Abe, Yoko Uchida, Shiomi Kanaizumi, Keiko Sakou, Hideomi Watanabe

    Journal of interprofessional care   27 ( 3 ) 261 - 8  2013.05  [International journal]

     View Summary

    The goal of effective interprofessional education (IPE) is high-quality patient-care delivery and attaining a high level of patient satisfaction in clinical settings. We aimed to examine if alumni who have studied in an IPE program at a pre-licensure stage maintain a positive attitude toward collaborative practice (CP) in the postgraduate clinical experience. This paper presents a cross-sectional descriptive study which employed the modified attitudes toward health care teams scale (ATHCTS) to examine the relationship between exposure to clinical practice and the attitudes toward interprofessional healthcare teams. Results indicated that the overall mean score of alumni was significantly lower than that of undergraduate students on the modified ATHCTS. Only "team efficacy" had a significantly lower regression factor score in alumni than undergraduate students. Our findings suggest that changes in professional identity in a team may be due to contact with patients after graduation in the postgraduate clinical healthcare experience. The reduction of attitudes toward healthcare teams in the postgraduate clinical experience may be related to "team efficacy". We emphasize the need for in-service IPE for sustaining attitudes and providing a useful CP, which results in good clinical outcome.

    DOI PubMed

  • Flexibility and Stent Fracture Potentials Against Cyclically Bending Coronary Artery Motions: Comparison Between 2-Link and 3-Link DESs.

    Iwasaki Kiyotaka, Kishigami Sho, Arai Jun, Ohba Takafumi, Zhu Xiaodong, Yamamoto Tadashi, Hikichi Yutaka, Umezu Mitsuo

    AMERICAN JOURNAL OF CARDIOLOGY   111 ( 7 ) 26B  2013.04  [Refereed]

    DOI

  • Prediction of Wall-thinning Area in Unruptured Intracerebral Aneurysms by Computational Fluid Dynamics

    Yoshifumi Hayashi, Takanobu Yagi, Yasutaka Tobe, Yuki Iwabuchi, Momoko Yamanashi, Kenji Takamura, Kiyotaka Iwasaki, Mitsuo Umezu, Takashi Ishida, Atsushi Nakajima, Hirotaka Yoshida, Kazutoshi Nishitani, Yoshihisa Ota, Michihito Sugawara, Yoshifumi Okada, Toshiro Kubo, Shigemi Kitahara

    STROKE   44 ( 2 )  2013.02  [Refereed]

  • Post-market Risk Assessment based on Malfunction Reports of Implantable Arrhythmia devices in Japan, Pharmaceutical and Medical Device Regulatory Science(医薬品医療機器レギュラトリーサイエンス)

    N.Okura, K.Iwasaki, H.Kasanuki

      44 ( 4 ) 352 - 356  2013

  • DuraHeart左心補助人工心臓システムの市販後における改良に関する報告

    中谷武嗣, 許俊鋭, 澤芳樹, 戸田宏一, 岩﨑清隆, 梅津光生, 山根隆志, 荒井裕国, 磯部光章, 小野稔, 山崎健二

    人工臓器   42 ( 3 ) 262 - 274  2013

    DOI

  • Tensile Strength of Human Pericardium Treated with Glutaraldehyde

    Hiromasa Yamashita, Shigeyuki Ozaki, Kiyotaka Iwasaki, Isamu Kawase, Yukinari Nozawa, Mitsuo Umezu

    ANNALS OF THORACIC AND CARDIOVASCULAR SURGERY   18 ( 5 ) 434 - 437  2012.10  [Refereed]

     View Summary

    Purpose: We have reconstructed aortic valves using autologous pericardium treated with glutaraldehyde since April 2007. However, the strength of the human pericardium has not been confirmed. We compared tensile strength between glutaraldehyde-treated human pericardium and aortic valve leaflets with various degrees of calcification to determine their suitability for use in aortic valve reconstruction.
    Methods: We measured the ultimate tensile strength and elasticity of samples of glutaraldehyde-treated pericardia (n = 8), non-calcified (n = 12), calcified (n = 9) and decalcified (n = 21) aortic leaflets collected from 23 patients who underwent aortic valve surgery. Aortic valves were decalcified using a cavitational ultrasonic surgical aspirator. The pericardium was immersed in 0.6% buffered glutaraldehyde for 10 minutes and then rinsed three times for 6 minutes each in normal saline.
    Results: The ultimate tensile strength of the glutaraldehyde-treated human pericardium, non-calcified, calcified and decalcified leaflets was 10, 2.8, 1.0 and 0.8 MPa, respectively.
    Conclusions: The ultimate tensile strength of glutaraldehyde-treated human pericardium was 4 times higher than non-calcified leaflets, indicating its suitability for application to aortic valve reconstruction. Calcified leaflets were slightly stronger than decalcified leaflets. Thus, calcification can be removed without altering the tensile strength of valve materials.

    DOI PubMed

  • Changes in attitudes toward interprofessional health care teams and education in the first- and third-year undergraduate students

    Tomoko Hayashi, Hiromitsu Shinozaki, Takatoshi Makino, Hatsue Ogawara, Yasuyoshi Asakawa, Kiyotaka Iwasaki, Tamiko Matsuda, Yumiko Abe, Fusae Tozato, Misako Koizumi, Takako Yasukawa, Bumsuk Lee, Kunihiko Hayashi, Hideomi Watanabe

    JOURNAL OF INTERPROFESSIONAL CARE   26 ( 2 ) 100 - 107  2012.03  [Refereed]

     View Summary

    The interprofessional education (IPE) program at Gunma University, Maebashi, Japan, implements a lecture style for the first-year students and a training style for the third-year students. Changes in the scores of modified Attitudes Toward Health Care Teams Scale (ATHCTS) and those of modified Readiness of health care students for Interprofessional Learning Scale (RIPLS) at the beginning and the end of the term were evaluated in the 2008 academic year. Two hundred and eighty-five respondents of a possible 364 completed the survey. In both the scales, the overall mean scores declined significantly after the lecture-style learning in the first-year students, while the scores improved significantly after the training-style learning in the third-year students. Exploratory factor analysis revealed that the modified ATHCTS was composed of three subscales, and the modified RIPLS two subscales. Analyses using regression factor scores revealed that the scores of "quality of care delivery" subscale in the modified ATHCTS and those of "expertise" subscale in the modified RIPLS declined significantly in the first-year students. Consequently, IPE programs may be introduced early in the undergraduate curriculum to prevent stereotyped perceptions for IPE, and comprehensive IPE curricula may result in profound changes in attitudes among participating students.

    DOI

  • INVESTIGATION ON A RELATIONSHIP BETWEEN HEMODYNAMICS AND WALL-THINNING IN AN UNRUPTURED HUMAN CEREBRAL ANEURYSM

    Yasutaka Tobe, Takanobu Yagi, Sara Takahashi, Yuki Iwabuchi, Momoko Yamanashi, Kiyotaka Iwasaki, Mitsuo Umezu, Yoshifumi Hayashi, Hirotaka Yoshida, Kazutoshi Nishitani, Yoshifumi Okada, Michihito Sugawara, Shin Hiraguchi, Toshiro Kubo, Shigemi Kitahara

    PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B     853 - 854  2012  [Refereed]

    DOI

  • Assessment of a Novel Stentless Mitral Valve Using a Pulsatile Mitral Valve Simulator

    Hitoshi Kasegawa, Kiyotaka Iwasaki, Shyunsuke Kusunose, Ryota Tatusta, Tetsuya Doi, Hiroki Yasuda, Mitsuo Umezu

    JOURNAL OF HEART VALVE DISEASE   21 ( 1 ) 71 - 75  2012.01  [Refereed]

     View Summary

    Background and aim of the study: The study aim was to develop a novel stentless mitral valve (SMV) and to evaluate its performance, using an original pulsatile simulator developed specifically to analyze the hydrodynamic function of the mitral valve.
    Methods: The SMV developed at the authors' institution consists of two major components: a large anterior leaflet with commissures, and a small posterior leaflet. The valve is formed by suturing the leaflets (made from bovine pericardium) to a flexible (Duran) ring. The SMV, constructed with a 27 mm flexible ring, was installed into the mitral valve simulator, after which the four papillary flaps of the two leaflets were sutured to artificial papillary muscles. The artificial ventricle was driven pneumatically at a pulse rate of 70 beats/min, with a systolic fraction of 35%. The mean flow, aortic pressure, and atrial pressure were adjusted to 4.5 l/min, 120/80 mmHg, and 10 mmHg, respectively. A 27 mm mechanical valve (MEV; St. Jude Medical Inc.) was employed as a control. The hydrodynamic performance of the SMV and MEV were investigated and compared. An echo-Doppler study was also performed.
    Results: The waveforms of the SMV and MEV showed a similar pattern. The mean transvalvular flow was 4.7 +/- 0.4 l/min for the SMV, and 3.55 +/- 0.13 l/min for the MEV (p &lt;0.001). Mitral regurgitation was 5.07 +/- 1.15 and 3.78 +/- 0.35 ml/beat, respectively (p &lt;0.05). Echocardiographic data indicated that the regurgitant jet towards the left atrial model was none or trivial for the SMV, and trivial for the MEV.
    Conclusion: Within the environment of the mitral valve simulator, the novel SMV prepared from bovine pericardium demonstrated excellent performance characteristics, and may represent a potential future alternative for bioprosthetic stented mitral valves.

    PubMed

  • 新しい僧帽弁ステントレス生体弁Normoの開発

    加瀬川均, 岩﨑清隆, 梅津光生

    人工臓器   41 ( 3 ) 176 - 179  2012

    DOI

  • Neointimal Coverage Reduces a Potential Risk of Stent Separation of Sirolimus Eluting Stent: Accelerated Durability Tests Under in-vivo Simulated Cyclically-Bended Proximal Right Coronary Artery Environment

    Kiyotaka Iwasaki, Yutaka Hikichi, Tadashi Yamamoto, Sho Kishigami, Jun Arai, Yusuke Noguchi, Hirhoshi Kasanuki, Mitsuo Umezu

    CIRCULATION   124 ( 21 )  2011.11  [Refereed]

  • Tissue engineered trachea using decellularized aorta

    AC Paz, K.Kojima, K.Iwasaki, JD Ross, M.Umezu

    J Bioengineer & Biomedical Sci.    2011

  • Assessment of a novel stentless mitral valve using a pulsatile mitral valve simulator

    H.Kasegawa, K.Iwasaki, S.Kusunose, R.Tatsuta, T.Doi, H.Yasuda, M.Umezu

    The J Heart Valve Dis   21 ( 1 ) 71 - 75  2011

  • 埋込み型補助人工心臓システムEVAHEARTの耐久性評価

    北野智哉, 宮越貴之, 小林信治, 得能敏正, 山崎健二, 岩﨑清隆, 梅津光生

    生体医工学   49 ( 6 ) 918 - 924  2011

    DOI

  • ヒト頚動脈病変の形状及び硬さを模擬した2層シリコーン狭窄血管モデルを用いたステントに必 要な拡張力に関する検討

    岡本吉弘, 田中智美, 小橋宏行, 犬飼孟, 山家弘雄, 岩﨑清隆, 梅津光生

    医工学治療   23 ( 3 ) 197 - 205  2011

  • 血管拡張ステントの加速耐久 試験に関する研究

    岩﨑清隆, 野口祐介, 岸上翔, 八木下雄一, 梅津光生

    豊田研究報告   64   117 - 120  2011

  • Two Stenting at Coronary Artery Bifurcation Yields Slow-Flow Region at Carina: In vitro Pulsatile Flow Investigation Using Elastic 3-Dimensional Stenotic Bifurcated Artery Replica

    Kiyotaka Iwasaki, Takanobu Yagi, Tadashi Yamamoto, Yuichi Yagishita, Manabu Shinke, Yusuke Noguchi, Sara Takahashi, Mitsuo Umezu

    CIRCULATION   122 ( 21 )  2010.11  [Refereed]

  • Comparing Accuracy of Cerebral Aneurysm Size Measurements From Three Routine Investigations: Computed Tomography, Magnetic Resonance Imaging, and Digital Subtraction Angiography

    Hiroyuki Takao, Yuichi Murayama, Toshihiro Ishibashi, Takayuki Saguchi, Masaki Ebara, Hideki Arakawa, Koreaki Irie, Kiyotaka Iwasaki, Mitsuo Umezu, Toshiaki Abe

    NEUROLOGIA MEDICO-CHIRURGICA   50 ( 10 ) 893 - 899  2010.10  [Refereed]

     View Summary

    Modern imaging technologies, such as computed tomography (CT) angiography, magnetic resonance (MR) angiography, and digital subtraction (DS) angiography are widely used for pretreatment evaluation of cerebral aneurysms, but the relative accuracies of these modalities are unclear. This study compared the measurements of aneurysm neck and dome height and width on CT angiography, time-of-flight (TOF)-MR angiography, and DS angiography using a three-dimensional workstation. An elastic model of a side-wall aneurysm was connected to an artificial heart pulsatile circuit system. The aneurysm model was prepared using a silicone membrane of 0.6-mm thickness under normal physiological circulation parameters. Using this aneurysm model, three-dimensional TOF-MR angiography, contrast-enhanced CT angiography, and DS angiography were performed. Source images were post-processed on a dedicated workstation to calculate the aneurysm size. DS angiography measurements were found to be the most accurate. In contrast, aneurysm neck sizes measured on CT angiography were significantly wider than actual values (p &lt; 0.05) and aneurysm heights measured using TOF-MR angiography were significantly lower than actual values (p &lt; 0.01). In this in-vitro model, at least one aneurysm dimension measured with CT angiography and with TOF-MR angiography differed significantly from actual values. Aneurysm neck width markedly affects therapeutic planning, as a wide neck requires craniotomy or endovascular treatment using an adjunctive device, so inaccuracies should be considered when aneurysm treatment is planned using modern methods of visualization.

    DOI PubMed

  • Recent Perspective on Coronary Bifurcation Intervention: Statement of the "Bifurcation Club in KOKURA"

    Yoshinobu Murasato, Yutaka Hikichi, Sunao Nakamura, Fumihiko Kajiya, Kiyotaka Iwasaki, Yoshihisa Kinoshita, Masahiro Yamawaki, Toshiro Shinke, Shnichiro Yamada, Takehiro Yamashita, Gim-Hooi Choo, Chang-Wook Nam, Young-Hak Kim, Nigel Jepson, Miroslaw Ferenc

    JOURNAL OF INTERVENTIONAL CARDIOLOGY   23 ( 4 ) 295 - 304  2010.08  [Refereed]

     View Summary

    The treatment of coronary bifurcation lesion remains a challenging issue even in the drug-eluting stent era. Frequent restenosis and stent thrombosis have been recently shown to be related not only to geometrical gap or stent structural deformation but also to rheological disturbance. Low wall shear stress at the lateral side of the bifurcation is likely to cause atherosclerotic changes due to easy access of the macrophages that induce chemical mediators. The turbulent flow over stent metal may facilitate accumulation of platelets, which results in thrombosis. The jailed strut and excess metal overlap may increase these risks. Since dramatic changes of the coronary flow pattern at the bifurcation are closely related to the genesis of atherosclerosis, future bifurcation intervention technique should be considered to restore the original physiological state as well as the anatomical structure.
    This article summarizes the global consensus of the members of the Asian Bifurcation Club and European Bifurcation Club at the KOKURA meeting. It also provides a perspective of basic sciences relating to bifurcation anatomy, physiology, and pathology, in the search for a best strategy for bifurcation intervention. (J Interven Cardiol 2010;23:295-304).

    DOI PubMed

  • Silicone Vascular Models for Analysis of Carotid Artery Stenting

    Y. Okamoto, H. Inukai, H. Kobashi, H. Yamaga, T. Yagi, K. Iwasaki, R. Shiurba, M. Umezu

    6TH WORLD CONGRESS OF BIOMECHANICS (WCB 2010), PTS 1-3   31   398 - +  2010

     View Summary

    Carotid artery stenting (CAS) is a minimally invasive surgical treatment for stenosis that is usually due to atherosclerotic plaque. Criteria to select an optimal stent for each clinical situation are lacking, however. Here we describe a surgical simulator that predicts vascular geometries after stenting using silicone rubber models of stenotic carotid arteries. Our objective was to develop the fabrication scheme of such vascular models. Herein, four CAS vascular models, or a soft plaque, two normal, and a hard one, were fabricated. By using rapid proto-typing of 3D CT angiographic data, we first made a patient-specific wax models with geometries that matched the lumen of carotid artery. Next, we fabricated a plaque model that matches patient-identical geometries. Then, we produced the each part using silicone rubber with different mechanical properties. In order to match the mechanical properties of the vessel model, pre- and post-stent geometry were compared in vivo and vitro using digital angiography. Moreover, we compared the stiffness of the vessel model by the Young's modulus. We first evaluated the mechanical properties of the vessel, and then that of the plaque. As for the former, the relationship between the expansion ratio and the stiffness parameter 11 was formulated by curve-fitting. We evaluated the mechanical properties of each plaque. It was found that the Young's modulus were 0.015, 0.092, 0.137, 0.503 N/m(2), for the soft, normal (two cases), and hard plaque, respectively. The largest difference was about 34 times for the soft and hard one. We achieved to develop a novel fabrication scheme for the carotid artery with atherosclerotic plaque. The validated vascular model featured two distinct mechanical properties for the vessel and plaque. Such models may help surgeons develop criteria to optimize CAS in a patient-specific manner.

    DOI

  • Experimental Investigation to Ensure a Safety of the Exchange of Extracorporeal-Type Ventricular Assist Devices in Long-Term-Use Patients

    T. Tanaka, R. Kume, S. Kusunose, R. Tatsuta, T. Igarashi, K. Ito, K. Iwasaki, M. Umezu

    6TH WORLD CONGRESS OF BIOMECHANICS (WCB 2010), PTS 1-3   31   378 - +  2010

     View Summary

    Ventricular assist devices (VADs) are widely applied for end-stage congestive heart failure patients. Considering the shortage of organs donations in Japan, VADs tend to be used for longer period. The extracorporeal-type Toyobo VAD has been used. Because the guarantee period of the Toyobo VAD is one month due to a potential risk of thrombus formation inside the VAD, it is necessary to exchange the VAD periodically in a long time. In the VAD exchange, the cable-ties are removed and the VAD used including stainless-steel connectors are replaced with a new VAD. In the case of the patient for long-term-usage who can move, there is a danger that the connection parts will be detached just after VAD exchange in case some kinds of loads are added to the VAD. Therefore, it is necessary for both patients and nurses to understand the quantitative load for the detachment of the VAD.
    In this study, we investigated the load required for the detachment of connectors from cannulae of the VAD before and after the VAD exchange. The VAD was incorporated in a mock circuit and pneumatically-driven in a 37 degrees C controlled water bath. In that condition, the load for the detachment of connectors from cannulae of the VAD was examined using a uni-axial tensile tester. As alternatives to cannulae used for a long time, plastically- deformed cannulae were prepared by heating at 120 degrees C for 7 hours. Influence of the tensile speed, direction of the load applied, and presence of liquid between the connectors and the cannulae on the loads necessary for the detachment were investigated.
    The load necessary for the detachment in one hour after the VAD exchange was decreased to 50-60% of the load before one. However, in 24 hours after the exchange, the load was recovered to 80% of the load before the VAD exchange. When the perpendicular load of 8.5kgf was applied at the tensile speed of 500mm/min, the time required for the detachment was only 6 seconds.
    It is important for nurses and patients to pay much attention in order to prevent load acting on the VAD newly changed, especially for one day after the VAD exchange.

    DOI

  • ステントの 至適拡張方法の検討:From bench to bedside

    上野高史, 光武良亮, 横山晋二, 板家直樹, 川崎友裕, 挽地裕, 岩﨑清隆

    人工臓器   39 ( 3 ) 222 - 226  2010

    DOI

  • Repeated 3-times-balloon-inflation for Stent Deployment Increases Luminal Patency of Cobalt Alloy Stent: In vitro Study Using 75% Stenotic Mechanically-equivalent Coronary Artery Replica

    Kiyotaka Iwasaki, Yutaro Hama, Yuichi Yagishita, Yusuke Noguchi, Syunsuke Tsubouchi, Yamamoto Tadashi, Mitsuo Umezu

    CIRCULATION   120 ( 18 ) S916 - S916  2009.11  [Refereed]

  • Systematic inclusion of mandatory interprofessional education in health professions curricula at Gunma University: a report of student self-assessment in a nine-year implementation

    Hatsue Ogawara, Tomoko Hayashi, Yasuyoshi Asakawa, Kiyotaka Iwasaki, Tamiko Matsuda, Yumiko Abe, Fusae Tozato, Takatoshi Makino, Misako Koizumi, Takako Yasukawa, Hideomi Watanabe

    HUMAN RESOURCES FOR HEALTH   7  2009.07  [Refereed]

     View Summary

    Background: The mandatory interprofessional education programme at Gunma University was initiated in 1999. This paper is a statistical evaluation of the programme from 1999 to 2007.
    Methods: A questionnaire of 10 items to assess the achievement levels of the programme, which was developed independently of other assessment systems published previously, was distributed, as well as two or three open-ended questions to be answered at the end of each annual module. A multivariate analysis of variance model was used, and the factor analysis of the responses was performed with varimax rotation.
    Results: Over all, 1418 respondents of a possible 1629 students completed the survey, for a total response rate of 87.1%. Cronbach's alpha of 10 items was 0.793, revealing high internal consistency. Our original questionnaire was categorized into four subscales as follows: "Role and responsibilities", "Teamwork and collaboration", "Structure and function of training facilities", and "Professional identity". Students in the Department of Occupational Therapy reached a relatively lower level of achievement. In the replies to the open-ended questions, requests for the participation of the medical students were repeated throughout the evaluation period.
    Conclusion: The present four subscales measure "understanding", and may take into account the development of interprofessional education programmes with clinical training in various facilities. The content and quality of clinical training subjects may be remarkably dependent on training facilities, suggesting the importance of full consultation mechanisms in the local network with the relevant educational institutes for medicine, health care and welfare.

    DOI

  • 臨床用補助人工心臓交換時の安全性に関する実験的研究

    田中隆, 古里正光, 石澤祐馬, 伊藤一彦, 岩崎清隆, 銭逸, 梅津光生

    体外循環技術   36 ( 2 ) 108 - 114  2009.06

  • Fabrication of Three-Dimensional Tissues with Perfused Microchannels

    Katsuhisa Sakaguchi, Tatsuya Shimizu, Kiyotaka Iwasaki, Masayuki Yamato, Mitsuo Umezu, Teruo Okano

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1213 - +  2009  [Refereed]

     View Summary

    Recently, researchers have challenged to create three-dimensional (3-D) tissues with tissue engineering technology in order to establish in vitro models and new therapy for damaged organ. We have developed cell-sheet based tissue engineering and successfully fabricated pulsatile 3-D myocardial tissues both in vivo and in vitro by layering cardiac cell sheets. However, in vitro scaling up of 3-D cell-dense tissues is limited due to lack of blood vessels supplying oxygen and nutrition and removing waste molecules. In this study, we have developed novel bioreactor culturing layered cell sheets on collagen-based microchannels and examined cell behavior between tissues and channels. Rat cardiac cells including endothelial cells were cultured on temperature responsible culture dishes for 4 days. By lowering temperature, confluent cardiac cells were harvested as an intact cell sheet and two cardiac cell sheets are layered. Collagen-based microchannels were engineered by gelling collagen around parallel stainless wires and extracting the wires. The double-layer cell sheets were put on the microchannels and the constructs were connected to the novel perfusion bioreactor. After 5 days of cultivation, the tissue sections were stained with Hematoxylin-Eosin and endothelial cell specific Isolectin B4. HE staining demonstrated that layered cell sheets tightly connected onto the collagen microchannels. The microchannels maintained their patency during culture period. The cardiac cells migrated into collagen gel and the number of migration increased flow-rate dependently. At higher flow-rate, some cardiac cells reached to microchannels and covered over their inner surface. Isolectin B4 staining showed endothelial cells formed networks within the cell sheets and also played as migrating cells. We have successfully fabricated 3-D tissues with perfused microchannels and tissue-originated cells migrated and communicated with the microchannels. These results showed new insights regarding in vitro vascular formation and indicated the possibility for fabricating vascularized 3-D tissues.

    DOI

  • Fabrication of Three-Dimensional Tissues with Perfused Microchannels

    Katsuhisa Sakaguchi, Tatsuya Shimizu, Kiyotaka Iwasaki, Masayuki Yamato, Mitsuo Umezu, Teruo Okano

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1213 - +  2009

     View Summary

    Recently, researchers have challenged to create three-dimensional (3-D) tissues with tissue engineering technology in order to establish in vitro models and new therapy for damaged organ. We have developed cell-sheet based tissue engineering and successfully fabricated pulsatile 3-D myocardial tissues both in vivo and in vitro by layering cardiac cell sheets. However, in vitro scaling up of 3-D cell-dense tissues is limited due to lack of blood vessels supplying oxygen and nutrition and removing waste molecules. In this study, we have developed novel bioreactor culturing layered cell sheets on collagen-based microchannels and examined cell behavior between tissues and channels. Rat cardiac cells including endothelial cells were cultured on temperature responsible culture dishes for 4 days. By lowering temperature, confluent cardiac cells were harvested as an intact cell sheet and two cardiac cell sheets are layered. Collagen-based microchannels were engineered by gelling collagen around parallel stainless wires and extracting the wires. The double-layer cell sheets were put on the microchannels and the constructs were connected to the novel perfusion bioreactor. After 5 days of cultivation, the tissue sections were stained with Hematoxylin-Eosin and endothelial cell specific Isolectin B4. HE staining demonstrated that layered cell sheets tightly connected onto the collagen microchannels. The microchannels maintained their patency during culture period. The cardiac cells migrated into collagen gel and the number of migration increased flow-rate dependently. At higher flow-rate, some cardiac cells reached to microchannels and covered over their inner surface. Isolectin B4 staining showed endothelial cells formed networks within the cell sheets and also played as migrating cells. We have successfully fabricated 3-D tissues with perfused microchannels and tissue-originated cells migrated and communicated with the microchannels. These results showed new insights regarding in vitro vascular formation and indicated the possibility for fabricating vascularized 3-D tissues.

    DOI

  • Biomedical Engineering Analysis of the Rupture Risk of Cerebral Aneurysms: Flow Comparison of Three Small Pre-ruptured Versus Six Large Unruptured Cases

    A. Kamoda, T. Yagi, A. Sato, Y. Qian, K. Iwasaki, M. Umezu, T. Akutsu, H. Takao, Y. Murayama

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1600 - +  2009

     View Summary

    A relationship between blood flows in cerebral aneurysms and their rupture remains obscure. In clinical practice, the size of aneurysms is one of the important factors for determining a strategy of treatment, but in our database three small aneurysms became ruptured during follow-up. Here, we aim to study their pre-ruptured hemodynamics, and differentiate them with those of six large unruptured aneurysms. All the aneurysms occurred in internal carotid artery, and their mean sizes were 6 and 10.8 mm for pre-ruptured and unruptured cases, respectively. We reproduced their replica as a patient-specific elastic model using clinical images obtained by digital subtraction angiography and a series of rapid proto-typing techniques. Flows were reproduced in vitro using a cerebral flow simulator, and visualized by Time-resolved Particle Image Velocimetry. All pre-ruptured cases showed the collision of an incoming flow at a distal neck, and formed a prominent jet stream directing towards the aneurismal head. In contrast, none of unruptured aneurysms had such a marked impingement, and their flows were most likely characterized by swirling patterns. All unruptured cases occurred in a twisted vessel, or carotid siphon, whereas pre-ruptured ones were located downstream whose geometries consisted of a simple curvature. These findings suggest that internal carotid artery has a regional dependency of the risk of aneurismal rupture. Furthermore, the presence of jet streams for small-sized aneurysms may be a substantial indicator of the rupture and immediate treatments.

    DOI

  • Microscale Visualization of Erythrocyte Deformation by Colliding with a Rigid Surface Using a High-Speed Impinging Jet

    S. Wakasa, T. Yagi, Y. Akimoto, N. Tokunaga, K. Iwasaki, M. Umezu

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1422 - +  2009

     View Summary

    Erythrocyte deformation by colliding with a rigid surface using a high-speed impinging jet was studied with microfluidic techniques. We aim to investigate the relevance of colliding erythrocytes with hemolysis. A micro-channel chip was made of polydimenthyl-siloxane (PDMS), which comprised a T- and V-shaped junction with a micro-nozzle and diffuser in order to attain a high-speed microflow with a jet velocity of m/s scale. A high-speed camera with a microscope imaged colliding erythrocytes by shadow imaging. Porcine erythrocyte with a hematocrit of 0.5% in phosphate buffer saline was utilized. At the Y-junction, erythrocytes showed buckling due to an impulsive, longitudinal, compressive deformation. Such anomalous phenomena were not detected at the T-junction, where erythrocytes underwent sequential compressions as approaching the colliding surface. Erythrocyte after buckling showed a hazy membrane while being released from the colliding surface, suggesting the ejection of hemoglobin out of the pore on a membrane. Flow-induced hemolysis has been considered as a model of viscous shear stress and exposure time. From our data, however, it was suggested that hemolysis due to a high-speed impinging flow characterized by mechanical heart valve flows may arise as an impulsive failure of erythrocyte membrane upon collision.

    DOI

  • New challenge for studying flow-induced blood damage: macroscale modeling and microscale verification

    T. Yagi, S. Wakasa, N. Tokunaga, Y. Akimoto, T. Akutsu, K. Iwasaki, M. Umezu

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1430 - +  2009

     View Summary

    Prosthetic heart valves often induce blood cell trauma, but its mechanism is not clearly understood due to the complexity of dynamical flows. We herein propose a new challenge, termed macroscale modeling and microscale verification. This report is the former, and here we aim to clarify the physical interpretation of Reynolds stress for flowing cells. One polymer and two mechanical valves are compared, and the Reynolds stress is visualized using a novel analytical technique including time-resolved particle image velocimetry and continuous wavelet transform. The method enables to analyze the dynamics of Reynolds stress in a spatial and temporal domain. As a result, it is found that the Reynolds stress should be considered as an indicator of impinging flows for circulating cells. Such flows may impulsively apply a colliding force on a membrane of flowing cells. As microscale verification based on this new hypothesis, we are currently investigating such collision phenomena of flowing cells using high-speed microfluidic techniques.

    DOI

  • In-vitro Evaluation Method to Measure the Radial Force of Various Stents

    Y. Okamoto, T. Tanaka, H. Kobashi, K. Iwasaki, M. Umezu

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1053 - +  2009

     View Summary

    Endovascular treatments of stenosis in carotid artery often utilize a self-expanding stent. There are a variety of stents commercially available. The radial force of a stent is a key parameter to characterize its mechanical property, but there is no reliable evaluation to standardize the force measurement. In measuring the radial force accurately, the stent deformation has to be uniform for the whole structure so as to ensure the force balance. Here we aim to develop such a measuring system of stent radial force, and compare the results with those obtained by conventional techniques.
    A developed device consisted of a tubular stent holder and a load measuring system. The Precise, Protege and Easy Wall stents with a diameter (D) of 10 mm were placed by a delivery system. Radial forces were measured with D = 8, 6, 5, and 4 mm at a temperature of 37 degrees. Maintaining the circular shape of stents was found to influence substantially the magnitude of radial force. The value increased about 80% at maximum for those measured by conventional techniques. These data show that the radial force has to be uniformly applied in a circumferential direction. Also, the Easy Wall stent showed a distinct tendency in contrast to the Precise and Protege stent. The Easy Wall stent was found to be placed with eliminating the axial variation of mesh geometries.
    These results indicate that the radial force measurements of stents have to ensure the uniform mesh geometry in both the axial and circumferential direction. It was concluded that our device can ensure the reliable measurement of stent radial forces.

    DOI

  • Development of Evaluation Test Method for the Possibility of Central Venous Catheter Perforation Caused by the Insertion Angle of a Guidewire and a Dilator

    M. Uematsu, M. Arita, K. Iwasaki, T. Tanaka, T. Ohta, M. Umezu, T. Tsuchiya

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1183 - +  2009

     View Summary

    The Seldinger technique is a well-established medical procedure to insert an indwelling device into blood vessel. Although the method is widely performed, various adverse effects due to the procedure have been reported. In order to improve safety, some hospitals originally compiled important reminders based on their experiences in an operation manual. The aim of our research is to provide evidences supporting failure behaviors with a mock system to promote awareness in clinical practice. This paper presents results of a newly developed test method to evaluate the possibility of perforation while inserting the dilator to the cervical vein after the guidewire placement.
    A tensile tester (AGI-250kN, Shimadzu Corp.) equipped with a load cell (SLBL-50N, Shimadzu Corp.) was utilized to measure the insertion force of a dilator to vein. The porcine vein was prepared to be aligned with 15mm and to be cut opened to expose the medial wall, and it was mounted on a custom-made device. A guidewire and a dilator were vertically suspended from the upper side of the tensile tester. During the dilator was approaching down to the vein through the guidewire at the constant velocity, the insertion force was measured and the tissue surface was observed simultaneously. The perforation force was examined in relation to the insertion angle from 15degrees to 60degrees.
    While veins were pressed only by a guidewire, perforation was not identified at all degrees. After inserting a dilator, veins were torn at 45degrees and at 60degrees more than ION. It was suggested that vessel wall could be thinner and be torn by multiple insertion. It is concluded that the usage situation of a guidewire and a dilator was assessed objectively and the angle-load relationship was quantified. The test would be helpful to propose safe approach for patients.

    DOI

  • Successful Reproduction of In-Vivo Fracture of an Endovascular Stent in Superficial Femoral Artery Utilizing a Novel Multi-loading Durability Test System

    K. Iwasaki, S. Tsubouchi, Y. Hama, M. Umezu

    13TH INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING, VOLS 1-3   23 ( 1-3 ) 1443 - +  2009

     View Summary

    Aim: High rates of stent fracture have been reported in the treatment of diseased superficial femoral artery (SFA). Understanding of in-vivo mechanical-loading environments, therefore, draws serious attention. We have developed a novel multi-loading durability tester which can apply cyclic twist and stretch on stents. Here, in-vitro stent fracture patterns were compared with stent fracture observed in vivo. Methods: The angle of cyclic twist as well as cyclic stretch exerted to the stents was regulated to physiologic conditions by utilizing referenced data of MR angiography of SFAs obtained in the spine and fetal position. Stiffness of the silicone vessel models were regulated to that of SFAs. As the SFAs are intrinsically stretched in vivo, stents were tested not only in the non-stretched vessel model but also in the 50% pre-stretched vessel model, respectively. The simultaneous cyclic multi-loads were exerted to the stents; under the mean luminal pressure of 100mmHg at 60 cycles per minute. Considering the data that average Japanese walk 7378 steps per day, the cyclic numbers of the in-vitro durability tests were converted to the equivalent durability in vivo. Results: Only minor fracture was observed at the stent strut after one-year-equivalent duration when the stents were tested using the non-stretched vessel models. However, employment of the novel pre-stretched vessel model resulted in complete stent fractures in the middle of longitudinal direction in 2-months-equivalent duration. Moreover, the fracture pattern was clearly coincident with the stent fracture in vivo. Conclusions: This is the first demonstration that the pre-stretch of vessel model is a requisite condition in durability tests of stents for SFA. Moreover, these results indicated that reproduction of multi-loading environments including cyclic twist and stretch is of great significance in order to obtain reliable durability data of endovascular stents for SFA.

    DOI

  • Calibration System for Pulse Spectrophotometry Using a Double-Layer Pulsation Flow-Cell

    M. Oura, N. Kobayashi, S. Yamamori, S. Takeda, K. Iwasaki, M. Umezu

    2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20     896 - +  2009

     View Summary

    We have studied noninvasive devices for measuring total hemoglobin and hemoglobin derivatives such as carboxyhemoglobin (COHb) and methemoglobin (MetHb). A calibration procedure needs to be developed to evaluate or calibrate these devices and pulse oximeters for clinical practice. However, people and animals are sometimes exposed to risk when they are used for calibration.
    In this paper, we propose a new in vitro calibration system for a pulse photometer. This system has a novel double-layer pulsation flow-cell that incorporates both venous and arterial blood flow. Using the calibration system, we are able to measure the in vitro pulsatile optical density ratio (Phi vt). The measured Phi vt agrees well with the in vivo pulsatile optical density ratio (Phi vt). This system simulates an in vivo environment with high accuracy and enables safe calibration. Consequently, the calibration system is able to standardize the performance and accuracy of pulse photometry.

    DOI

  • 3次元心筋組織構築のためのバイオリアクターの開発

    坂口勝久, 沢田里智, 清水達也, 岩崎清隆, 大和雅之, 梅津光生, 岡野光夫

    ライフサポート     104 - 109  2009

    DOI

  • Calibration System for Pulse Spectrophotometry Using a Double-Layer Pulsation Flow-Cell

    M. Oura, N. Kobayashi, S. Yamamori, S. Takeda, K. Iwasaki, M. Umezu

    2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20     896 - +  2009

     View Summary

    We have studied noninvasive devices for measuring total hemoglobin and hemoglobin derivatives such as carboxyhemoglobin (COHb) and methemoglobin (MetHb). A calibration procedure needs to be developed to evaluate or calibrate these devices and pulse oximeters for clinical practice. However, people and animals are sometimes exposed to risk when they are used for calibration.
    In this paper, we propose a new in vitro calibration system for a pulse photometer. This system has a novel double-layer pulsation flow-cell that incorporates both venous and arterial blood flow. Using the calibration system, we are able to measure the in vitro pulsatile optical density ratio (Phi vt). The measured Phi vt agrees well with the in vivo pulsatile optical density ratio (Phi vt). This system simulates an in vivo environment with high accuracy and enables safe calibration. Consequently, the calibration system is able to standardize the performance and accuracy of pulse photometry.

    DOI

  • Bioengineered three-layered robust and elastic artery using hemodynamically-equivalent pulsatile bioreactor

    Kiyotaka Iwasaki, Koji Kojima, Shohta Kodama, Ana C. Paz, Melody Chambers, Mitsuo Umezu, Charles A. Vacanti

    CIRCULATION   118 ( 14 ) S52 - S57  2008.09  [Refereed]

     View Summary

    Background-There is an essential demand for tissue engineered autologous small-diameter vascular graft, which can function in arterial high pressure and flow circulation. We investigated the potential to engineer a three-layered robust and elastic artery using a novel hemodynamically-equivalent pulsatile bioreactor.
    Methods and Results-Endothelial cells (ECs), smooth muscle cells (SMCs), and fibroblasts were harvested from bovine aorta. A polyglycolic acid (PGA) sheet and a polycaprolactone sheet seeded with SMCs, and a PGA sheet seeded with fibroblast, were wrapped in turn on a 6-mm diameter silicone tube and incubated in culture medium for 30 days. The supporting tube was removed, and the lumen was seeded with ECs and incubated for another 2 days. The pulsatile bioreactor culture, under regulated gradual increase in flow and pressure from 0.2 (0.5/0) L/min and 20 (40/15) mm Hg to 0.6 (1.4/0.2) L/min and 100 (120/80) mm Hg, was performed for an additional 2 weeks (n=10). The engineered vessels acquired distinctly similar appearance and elasticity as native arteries. Scanning electron microscopic examination and Von Willebrand factor staining demonstrated the presence of ECs spread over the lumen. Elastica Van Gieson and Masson Tricrome Stain revealed ample production of elastin and collagen in the engineered grafts. Alpha-SMA and calponin staining showed the presence of SMCs. Tensile tests demonstrated that engineered vessels acquired equivalent ultimate strength and similar elastic characteristics as native arteries (Ultimate Strength of Native: 882 +/- 133 kPa, Engineered: 827 +/- 155 kPa, each n=8).
    Conclusions-A robust and elastic small-diameter artery was engineered from three types of vascular cells using the physiological pulsatile bioreactor.

    DOI PubMed

  • 本邦初の次世代型補助人工心臓EVAHEART-自宅療養・就労復帰が可能となった

    山嵜健二, 梅津光生, 太田英輔, 富岡淳, 岩﨑清隆, 石原一彦

    油空圧技術     12 - 16  2008

  • Development of a Compact Mock Circulation System and a New Flow-Cell Model for Pulse Spectrophotometry

    M. Oura, N. Kobayashi, S. Takeda, K. Iwasaki, M. Umezu

    2008 30TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-8     670 - +  2008

     View Summary

    We have developed an extremely compact mock circulation system. This system can simulate artery blood circulation and generate a pulse wave with a very small amount of blood. We were also able to measure the in vitro pulsatile optical density ratio (phi vt) using this system with a flow cell [1]. Results showed a difference between phi vt and the in vivo pulsatile optical density ratio (phi vi) for the same oxygen saturations. To explain this difference, we proposed a new flow-cell model that includes venous flow and arterial flow. Because these systems can simulate the in vivo environment with very accurately, they can be applied to various pulse spectrophotometry studies. Moreover, the required blood volume is very small so the system can evaluate artificial blood or artificial red cells at very low cost. Thus, this system can reduce the time and cost of developing new pulse photometry techniques and other medical equipment.

  • 冠動脈バイパス手術における血管吻合手技の定量かに向けた基礎検討

    回日本コンピュータ外科学会大会, 回コンピュータ支援画像診断学会大会, 合同論文集

        83 - 84  2007.11

  • Tissue engineered three-layered artery using hemodynamically-equivalent pulsatile bioreactor

    Kiyotaka Iwasaki, Koji Kojima, Shota Kodama, Cristina Paz, Melody A. Chambers, Mitsuo Umezu, Charles A. Vacanti

    CIRCULATION   116 ( 16 ) 685 - 685  2007.10  [Refereed]

  • 量産向け旋回渦流型人工心臓内面検査装置の開発

    田中隆, 古里正光, 石澤祐馬, 伊藤一彦, 岩﨑清隆, 梅津光生

    第5回生活支援工学系学会連合大会講演予稿集     24  2007.10

    DOI

  • 走査型ステレオPIV法を用いた異なる大動脈バルサルバ洞形状をもつ Valved Graft 内の3次元流動特性

    八木高伸, 若狭翔太郎, William Yang, 岩﨑清隆, 梅津光生

    日本機械学会創立110周年記念2007年度年次大会講演論文集   5   295 - 296  2007.09

  • In vivo複合負荷環境を模擬した加速試験装置による末梢ステントの耐久試験

    岩﨑清隆, 錦織晃, 坪内俊介, 梅津光生

    日本機械学会創立110周年記念2007年度年次大会講演論文集   5   301 - 302  2007.09

  • Characteristics of spiral vortex pump driven by two different drivers

    Ito K, Sudo T, Shima T, Kouno Y, Ohnishi Y, Tanaka T, Iwasaki K, Fujimoto T, Umezu M

    Biocybernetics and Biomedical Engineering   27 ( 1月2日 ) 121 - 132  2007.06

  • Japanese-made implantable centrifugal type ventricular assist system(LVAS):EVAHEART

    Umezu M, Yamazaki K, Yamazaki S, Iwasaki K, Miyakoshi T, Kitano T, Tokono T

    Biocybernetics and Biomedical Engineering, Polish Academy of Sciences Institute of Biocybernetics and Biomedical Engineering   27 ( 1月2日 ) 111 - 119  2007.06

  • 再生医療を支える最先端技術と将来への展望

    梅津光生, 岩﨑清隆

    第5回薬事エキスパート研修会 要旨集     8 - 11  2007.02

  • Investigation of a hydrodynamic performance of a ventricular assist device after its long-term use in clinical application

    Yuma Kokuzawa, Tomohiro Shima, Masateru Furusato, Kazuhiko Ito, Takashi Tanaka, Toshibiro Igarashi, Tomohiro Nishinaka, Kiyotaka Iwasaki, Mitsuo Umezu

    Life System Modeling and Simulation, Proceedings   4689   429 - 435  2007  [Refereed]

     View Summary

    A long-term durability of a ventricular assist device (VAD) is required due to a shortage of donor hearts for cardiac transplantation, but there is no analyzed pump data after long-term use. This study aimed to perform a comparative study between new VAD and VADs after long-term use. The hydrodynamic performance of the used Toyobo VADs (mean period of 5 months with the maximum of 12 months) was evaluated in a mock circulatory system, where a new VAD was used as a control. Although a remarkable difference was not observed in terms of mean flow rate, flow and pressure waveforms varied significantly. Then, the pressure-volume relationship of each pump was measured: It was found that the capacity of long-term VADs was reduced. Although a further study is required, these results suggested that a long-term use of VAD may cause a change in mechanical properties of polymer materials.

    DOI

  • Coil compaction予測のための時系列PIV法を用いた実形状弾性脳動脈瘤モデル内の流れの可視化

    松本徹, 岩﨑清隆, 八木高伸, 福島桃子, 鴨田明憲, 梅津光生, 阿久津敏乃介, 高尾洋之, 石橋敏寛, 村山雄一

    第19回バイオエンジニアリング講演会 講演論文集     82 - 83  2007.01

  • 脳血管系疾患のCFDによる解析:PIV可視化実験とのValidation

    原田哲司, 福井弘一, 銭逸, 岩﨑清隆, 梅津光生, 高尾洋之, 石橋敏寛, 村山雄一

    第19回バイオエンジニアリング講演会 講演論文集     88 - 89  2007.01

  • 末梢Stent耐久性能評価を目的としたねじり型加速疲労試験装置の開発

    第19回バイオエンジニアリング講演会 講演論文集     80 - 81  2007.01

  • ステレオPIV法を用いた大動脈バルサルバ洞内の3次元流れ場構造に関する基礎知識

    須藤宏幸, 八木高伸, 石川大輔, 若狭翔太朗, William Yang, 岩﨑清隆, 梅津光生

    第19回バイオエンジニアリング講演会 講演論文集     62 - 63  2007.01

  • リアルタイム周波数解析を用いた人工弁閉鎖時に発達する瞬時高周波ストレスの検討

    石川大輔, 八木高伸, 須藤宏幸, 若狭翔太朗, 阿久津敏乃介, 岩﨑清隆, 梅津光生

    第19回バイオエンジニアリング講演会 講演論文集     60 - 61  2007.01

  • 組織工学と再生医療

    岩﨑清隆

    人工臓器36(3)     213 - 214  2007

  • Investigation of a hydrodynamic performance of a ventricular assist device after its long-term use in clinical application

    Yuma Kokuzawa, Tomohiro Shima, Masateru Furusato, Kazuhiko Ito, Takashi Tanaka, Toshibiro Igarashi, Tomohiro Nishinaka, Kiyotaka Iwasaki, Mitsuo Umezu

    Life System Modeling and Simulation, Proceedings   4689   429 - 435  2007

     View Summary

    A long-term durability of a ventricular assist device (VAD) is required due to a shortage of donor hearts for cardiac transplantation, but there is no analyzed pump data after long-term use. This study aimed to perform a comparative study between new VAD and VADs after long-term use. The hydrodynamic performance of the used Toyobo VADs (mean period of 5 months with the maximum of 12 months) was evaluated in a mock circulatory system, where a new VAD was used as a control. Although a remarkable difference was not observed in terms of mean flow rate, flow and pressure waveforms varied significantly. Then, the pressure-volume relationship of each pump was measured: It was found that the capacity of long-term VADs was reduced. Although a further study is required, these results suggested that a long-term use of VAD may cause a change in mechanical properties of polymer materials.

  • A reproduction of inflow restriction in the mock circulatory system to evaluate a hydrodynamic performance of a ventricular assist device in practical conditions

    Masateru Furusato, Tomohiro Shima, Yuma Kokuzawa, Kazuhiko Ito, Takashi Tanaka, Kiyotaka Iwasaki, Yi Qian, Mitsuo Umezu, ZhiKun Yan, Ling Zhu

    LIFE SYSTEM MODELING AND SIMULATION, PROCEEDINGS   4689   553 - +  2007  [Refereed]

     View Summary

    A novel in vitro mock circulatory system, which enables to reproduce an inflow restriction, simulating blood volume pooling due to heart failure, was developed to evaluate a hydrodynamic performance of a pulsatile ventricular assist device (VAD) in practical conditions. The concept of this development was motivated by a difference of an inflow restriction between in vitro and in vivo environments. The major idea of this study is to reproduce an inflow restriction by using a centrifugal pump placed at an inflow side of a left ventricular model instead of a constant head reservoir in a conventional circuit. In the novel circuit, the maximum flow rate was obtained at lower systolic fraction as compared with a conventional circuit. This similar tendency by the novel one was observed in an acute animal experiment in sheep. This result suggests that a new mock circuit is effective to confirm a practical drive strategy of the VAD for various diseased conditions.

    DOI

  • Tensile test to ensure a safety of cannula connection in clinical ventricular assist device (VAD)

    Takashi Tanaka, Tomohiro Shima, Masateru Furusato, Yuma Kokuzawa, Kazuhiko Ito, Kiyotaka Iwasaki, Yi Qian, Mitsuo Umezu

    LIFE SYSTEM MODELING AND SIMULATION, PROCEEDINGS   4689   546 - +  2007  [Refereed]

     View Summary

    A pneumatic driven ventricular assist device (VAD) is not only designed for short-term usage of a "bridge to recovery" (BTR) in cardiac function recovery, but also developed to apply as a "bridge to transplantation" (BTT) for cardiac transplant. However, in the latter, the VAD must be exchanged before its expiries of guarantee. In this research, the authors have investigated the connector's strength between connector and cannula, and safety during the VAD exchange.

    DOI

  • Three-dimensional fluid mechanics of the sinus of Valsalva with a bileaflet mechanical heart valve

    Takanobu Yagi, Daisuke Ishikawa, Hiroyuki Sudo, Shotaro Wakasa, William Yang, Kiyotaka Iwasaki, Mitsuo Umezu

    PROCEEDING OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2007     187 - 188  2007  [Refereed]

  • Biomedical engineering analysis of effectiveness of cardiovascular surgery: Anastomosis methods for coronary artery bypass grafting

    Umezu M, Kawai J, Suehiro J, Arita M, Shiraishi Y, Iwasaki K, Tanaka T, Akutsu T, Niinami H

    Biocybernetics and biomedical engineering 2006   26 ( 1 ) 61 - 67  2006.02

  • Noninvasive measurement of total hemoglobin and hemoglobin derivatives using multiwavelength pulse spectrophotometry - In vitro study with a mock circulatory system

    Hironori Suzaki, Naoki Kobayashi, Takashi Nagaoka, Kiyotaka Iwasaki, Mitsuo Umezu, Sunao Takeda, Tatsuo Togawa

    2006 28TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-15   1   3451 - +  2006  [Refereed]

     View Summary

    Total hemoglobin (tHb), carboxyhemoglobin (COHb), and methemoglobin (MetHb) are usually measured with a CO-oximeter. Noninvasive and continuous measurement of these blood components is expected to decrease the pain of a patient. Therefore, we developed an instrument to measure oxygen saturation (SpO(2)), tHb, COHb, and MetHb noninvasively. Multiwavelength LED (600, 625, 660, 760, 800, 940, and 1306 nm) and a combined detector (Si, InGaAs) were built into the instrument (Seven wavelengths transparent pulse spectrophotometer). We used the Waseda mock circulatory system, which can simulate blood circulation in tissues and generate a pulse wave mechanically, to estimate the instrument's performance. Furthermore we proposed new calculation formula including DC components of optical density (this method). Under conditions without any change of other components, the mean error standard deviation between this method and the CO-oximetry were SaO(2)=0.0 +/- 1.4%, tHb=0.0 +/- 0.0 g/dl, COHb = 0.0 +/- 2.0%, and MetHb=0.0 +/- 0.3%. When the concentration of other components was changed, this method showed mean errors and standard deviations of SaO(2)=0.2 +/- 1.6%, tHb=0.0 +/- 0.4 g/dl, COHb=0.5 +/- 4.1%, and MetHb = 0.0 +/- 03%.

    DOI PubMed

  • Noninvasive measurement of total hemoglobin and hemoglobin derivatives using multiwavelength pulse spectrophotometry -In vitro study with a mock circulatory system-

    Hironori Suzaki, Naoki Kobayashi, Takashi Nagaoka, Kiyotaka Iwasaki, Mitsuo Umezu, Sunao Takeda, Tatsuo Togawa

    Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings     799 - 802  2006  [Refereed]

     View Summary

    Total hemoglobin (tHb), carboxyhemoglobin (COHb), and methemoglobin (MetHb) are usually measured with a CO-oximeter. Noninvasive and continuous measurement of these blood components is expected to decrease the pain of a patient. Therefore, we developed an instrument to measure oxygen saturation (SpO 2), tHb, COHb, and MetHb non-invasively. Multiwavelength LED (600, 625, 660, 760, 800, 940, and 1300 nm) and a combined detector (Si, InGaAs) were built into the instrument (Seven wavelengths transparent pulse spectrophotometer). We used the Waseda mock circulatory system, which can simulate blood circulation in tissues and generate a pulse wave mechanically, to estimate the instrument's performance. Furthermore we proposed new calculation formula including DC components of optical density (this method). Under conditions without any change of other components, the mean error ± standard deviation between this method and the CO-oximetry were SaO 2=0.0±1.4%, tHb=0.0±0.0 g/dl, COHb=0.0±2.0%, and MetHb=0.0±0.3%. When the concentration of other components was changed, this method showed mean errors and standard deviations of SaO 2=0.2±1.6%, tHb=0.0±0.4 g/dl, COHb=0.5±4.1%, and MetHb=0.0±0.3%. © 2006 IEEE.

    DOI PubMed

  • Stereoscopic particle image velocimetry for application in three-dimensional flow within a spiral vortex pulsatile blood pump

    Yagi T, Yang W, Ishikawa D, Iwasaki K, Umezu M

    Biocybernetics and Biomedical Engineering   26 ( 2 ) 39 - 48  2006

  • 3D quantitative flow visualization of a spiral vortex pulsatile blood pump using stereoscopic PIV

    Yang W, Yagi T, Ishikawa D, Sudo H, Iwasaki K, Umezu M, Tu JY

    Proceedings of the 12th International Symposium on Flow Visualization    2006

  • Real-time planar spectral analysis of instantaneous high-frequency stress on blood cells downstream of an artificial heart valve

    Yagi T, Ishikawa D, Sudo H, Yang W, Iwasaki K, Umezu M

    Proceedings of the 12th International Symposium on Flow Visualization    2006

  • Development of "patient robot"; Measurement system of myocardial behaviors for the quantitative evaluation of the surgical robot technology

    Miyuki Uematsu, Hayato Ando, Atsushi Morita, Sigeru Uesugi, Kiyotaka Iwasaki, Mitsuo Umezu, Yasuyuki Shiraishi

    2006 1ST IEEE RAS-EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS, VOLS 1-3     1172 - +  2006  [Refereed]

     View Summary

    Aiming to contribute an improvement of medical robot technology, the authors have been developing a new evaluation method on cardiac function, which is based on surface measurement of the heart. This system will be able to evaluate a function of surgical robot in the future. As the preliminary study, an animal experiment was performed to examine various cardiac functions under normal pulsatile and arrhythmic conditions. The physical data such as electrocardiogram, blood flow and pressure were simultaneously obtained and compared with this approach. It was found that there was a difference in displacements and phases from control to arrhythmia. With the physical data, it was confirmed that strain change in regional area was coincident with a contraction of natural heart. Moreover, the fusion images allowed us to understand the superficial strain of regional areas differs among the various heart functions visually. In the near future, this method will be effective for the improvement of real surgery as well as the advancement of the surgical robot technology.

    DOI

  • Multiplane scanning Stereo-PIV measurements of flow inside a spiral vortex pulsatile blood pump

    Yagi.T, Yang W, Ishikawa D, Sudo H, Iwasaki K, Umezu M

    Proceedings of the 13th International Symposium on Applications of Laser Techniques to Fluid Mechanics   ( 2006 )  2006

  • Relation between hematocrit and optical density in pulse oximetry -In vitro study with Waseda mock circulatory system-

    H. Suzaki, S. Takeda, N. Kobayashi, H. Kubota, T. Aomi, T. Nagaoka, K. Iwasaki, M. Umezu, A. Uchiyama

    2005 IEEE Engineering in Medicine and Biology 27th Annual Conference   7 VOLS   2626 - 2629  2005.12  [Refereed]

     View Summary

    Optical properties of living tissues have not been well established even today, and bioopticinstrumentations have to be based on empirical formulae. In order to examine optical properties of the tissue having pulsating blood perfusion, we investigated the relation between optical density (defined as O.D.) of whole blood and hematocrit by transmission spectrophotometry. We used Waseda mock circulatory system that simulates blood circulation in the tissue. It was found that with increasing light path length, O.D. per unit light path length due to scattering and absorption effect, tended to become constant in each hematocrit. For wavelengths of 660, 805 and 940 nm, the relations between O.D. of whole blood and hematocrit predicted by Twersky&#039;s equation, Loewinger&#039;s equation and photon diffusion equation fitted to the data obtained. Meanwhile, for 1300 nm, the relation predicted by Loewinger&#039;s equation gave the best fit to the data. © 2005 IEEE.

    DOI

  • 左心室形成術における切除線決定のための診断法に関する基礎的検討

    植松美幸, 白石泰之, 関根一光, 山家智之, 西條芳文, 安藤隼人, 朴栄光, 武田朴, 岩﨑清隆, 梅津光生

    生体医工学   43 ( 4 ) 653 - 660  2005.12

    DOI

  • Stereoscopic particle image velocimetry measurements toward three dimensional flow investigations within the spiral vortex blood pump "jointly worked"

    Yagi T, Yang W, Ishikawa D, Iwasaki K, Umezu M

    Lecture Notes of the ICB Seminar 8th Polish-Japanese Seminar on New Technologies For Future Artificial Organs     106 - 112  2005.08

  • Biomedical engineering analysis on the effectiveness of cardiovascular surgery: Anastomosis methods for coronary artery bypass grafting "jointly worked"

    Umezu M, Kawai J, Suehiro J, Arita M, Shiraishi Y, Iwasaki K, Tanak T, Akutsu T, Niinami H

    Lecture Notes of the ICB Seminar 7th Polish-Japanese Seminar on New Technologies For Future Artificial Organs     80 - 86  2005.08

  • An innovative approach to evaluate a cardiac function based on surface measurement.

    Uematsu M, Shiraishi Y, Sekine K, Yambe T, Saijo Y, Park Y, Ando H, Matsumoto T, Takeda S, Iwasaki K, Umezu M

    Conf Proc IEEE Eng Med Biol Soc   7   7640 - 7643  2005.04  [Refereed]

  • 様々な負荷に対する心機能変化計測への試み

    植松美幸, 白石泰之, 関根一光, 山家智之, 西條芳文, 武藤俊介, 朴栄光, 安藤隼人, 松本徹, 武田朴, 岩崎清隆, 梅津光生, 内山明彦

    電気学会研究会資料     23 - 26  2005.02

  • 脳動脈瘤治療法の評価を目的とした拍動循環シミュレータの開発

    栗山仁志, 岩崎清隆, 八木高伸, 高島俊洋, 藤井麻由, 石川大輔, 梅津光生, 阿久津敏乃介, 高尾洋之, 石橋敏寛, 村山雄一

    第17回バイオエンジニアリング講演会 講演論文集     397 - 398  2005.01

  • Influence of drive conditions on hemodynamic performance of undulation type artificial heart

    Sone D, Yada Y, Iwasaki K, Saito I, Umezu M, Abe Y, Imachi K

    Proceedings of 12th International Conference on Biomedical Engineering   12   1A3 - 04  2005

  • An investigation of instantaneous high-frequency turbulent stress in the vicinity of artificial heart valves using wavelet transform analysis of dynamic PIV measurements

    Yagi T, Ishikawa D, Sudo H, Akutsu T, Yang W, Iwasaki K, Umezu M

    Proceedings of 12th International Conference on Biomedical Engineering   12   1B2 - 06  2005

  • An experimental investigation of three-dimensional flow structures within the spiral vortex ventricular assist device using stereoscopic PIV

    Yagi T, Yang W, Ishikawa D, Sudo H, Iwasaki K, Umezu M

    Proceedings of 12th International Conference on Biomedical Engineering   12   1A3 - 06  2005

  • Development of an inexpensive first-aid type ventricular assist device driven by IABP consoles

    Sudo T, Iwasaki K, Ohnishi Y, Shima T, Tanaka T, Ito K, Umezu M

    Proceedings of 12th International Conference on Biomedical Engineering   12   1A3 - 05  2005

  • Innovative bioreactor technologies produced a completely decellularized and pre-endothelialized functional aortic valve

    Iwasaki K, Ozaki S, Kawai T, Yamaguchi S, Eto M, Ohba Y, Umezu M

    Proceedings of 12th International Conference on Biomedical Engineering   12   1A2 - 07  2005

  • 人工弁

    岩崎清隆, 梅津光生

    人工臓器   33 ( 3 ) 178 - 186  2004.12

    DOI

  • Present status of Japanese implantable centrifugsl type ventricular assit system(LVAS):Evaheart

    Umezu M, Yamazaki K, Yamazaki S, Kurasawa H, Iwasaki K

    First Shanghai congress on heart assist and mechanical circulatory support     27 - 29  2004.12

  • In vitro hydrodynamic test and in vitro hemolysis test for development of inexpensive spiral vortex ventricular assisting system using IABP console

    OHNISHI Y, IWASAKI K, MIZUTA H, SUDO T, MUTO S, SHIMA T, TANAKA T, ITO K, UMEZU M

    Journal of Shanghai University 2004   10   32 - 36  2004.10

  • In vitro mitral simulator to evaluate effectiveness of valvoplasty technique

    Doi H, Arita M, Okuda M, Noda R, Iwasaki K, Tanaka T, Kasegawa H, Umezu M

    Journal of Shanghai University 2004   10   29 - 31  2004.10

  • Biomedical engineering approach to evaluate anastomosis methods for coronary artery bypass grafting

    Umezu M, Kawai J, Suehiro J, Arita M, Shiraishi Y, Iwasaki K, Tanaka T, Niinami H

    Journal of Shanghai University 2004   10   25 - 28  2004.10

  • 旋廻渦流型人工心臓量産化のための金型形状の検討

    田中隆, 岩﨑清隆, 伊藤一彦, 梅津光生

    第2回生活支援工学系学会連合大会講演予稿集     203 - 204  2004.09

    DOI

  • 拍動型人工心臓材料のin vitro血液適応性評価方法の検討

    竹内有理, 岩﨑清隆, 佐伯航, 石原一彦, 梅津光生

    第2回生活支援工学系学会連合大会講演予稿集     157 - 158  2004.09

    DOI

  • 低価格旋廻渦流型拍動血液ポンプの製作法の検討

    須藤知浩, 岩﨑清隆, 吉田敬, 田中隆, 伊藤一彦, 梅津光生

    第2回生活支援工学系学会連合大会講演予稿集     155 - 156  2004.09

    DOI

  • Effect of the elastic conditions around a stentless valvular bioprosthesis on opening behavior

    Tetsuo Fujimoto, Daisuke Kawaguchi, Yasuyuki Shiraishi, Kiyotaka Iwasaki, Makoto Arita, Takashi Tanaka, Mitsuo Umezu

    Journal of Artificial Organs   7 ( 3 ) 133 - 136  2004.09  [Refereed]

     View Summary

    Stentless valvular bioprostheses have been used clinically for over 8 years and the excellent properties of the bioprostheses have been demonstrated in clinical studies. The present study examined how differing elastic conditions around the bioprosthesis at the aortic position affect the hydrodynamic characteristics of the bioprosthesis. Bioprosthesis implantation is typically performed using either the subcoronary or the full-root technique. These procedures for implanting a stentless prosthetic heart valve at the aortic root were hydrodynamically evaluated in a mock circulatory system. Forward flow rate was 11% greater with the subcoronary technique than with the full-root technique. In a high-speed video camera study, the orifice area at full opening was 12% larger for the subcoronary technique than for the full-root technique. Evaluation of bioprosthetic characteristics in terms of mechanical conditions is important when considering surgical options.

    DOI PubMed

  • CMCの医療機器応用への期待

    梅津光生, 朴栄光, 松本徹, 岩﨑清隆, 田中隆, O Medvedev, 藤江正克, 高西淳夫, 山川宏, 元島栖二

    第15回カーボンマイクロコイル(CMC)研究会     19 - 22  2004.06

  • CMC内蔵型シリコン管の製作と性能

    朴栄光, 梅津光生, 松本徹, 岩﨑清隆, 田中隆, O Medvedev, 青見茂之, 元島栖二

    第15回カーボンマイクロコイル(CMC)研究会     37 - 40  2004.06

  • 人工心臓26題

    梅津 光生, 見藤 歩, 八木 高伸, 岩崎 清隆, 小堀 賢司, 今井 浩二, 福長 一義

    人工臓器   33 ( 2 ) s146 - s148  2004

    DOI CiNii

  • 医用高分子材料の長期血液循環使用下で問題となるカルシウム沈着特性のin vitro 評価試験手法の新開発

    岩崎清隆, 梅津光生, 井上旭, 井街宏

    日本機械学会第16回バイオエンジニアリング講演会講演論文集     219 - 220  2004.01

  • 新規の完全大気非接触型拍動動流循環回路による人工臓器のin vitro抗血栓性評価方法の確立に向けての挑戦

    岩崎清隆, 佐伯航, 竹内有理, 梅津光生, 石原一彦, 井街宏, 桜井靖久

    日本機械学会第16回バイオエンジニアリング講演会講演論文集     217 - 218  2004.01

  • 脱細胞化異種大動脈弁の開発:拍動循環下でのマイクロ波均一照射による完全脱細胞化および拍動循環での組織再内皮細胞化手法の検討

    岩崎清隆, 尾崎重之, 中澤剛, 今井裕一, 川井貴裕, 石原雅之, 守本裕司, 菊地眞, 梅津光生

    日本機械学会第16回バイオエンジニアリング講演会講演論文集     437 - 438  2004.01

  • 心臓病の治療効果評価のための左心系モデルの開発

    野口康雄, 梅津光生, 岩崎清隆

    日本機械学会第16回バイオエンジニアリング講演会講演論文集     63 - 64  2004.01

  • 人工弁の最新の進歩

    尾崎重之, 菊地眞, 岩崎清隆, 守本裕司

    バイオマテリアル   22 ( 2 ) 89 - 98  2004

  • 人工弁,人工臓器—最近の進歩

    岩﨑清隆, 梅津光生

    人工臓器   33 ( 3 ) 178 - 186  2004

    DOI

  • 人工弁の最近の進歩

    尾崎重之, 菊地眞, 岩﨑清隆, 守本裕司

    バイオマテリアル   22 ( 2 ) 89 - 98  2004

  • In vitro evaluating system for prosthetic heart valves

    Fujimoto T, Tsutsumi Y, Kawaguchi D, Shiraishi Y, Iwasaki K, Arita M, Umezu M

    芝浦工業大学学術フロンティア推進事業2002年度研究成果報告     17 - 26  2003.12

  • Advance in animal experiments with the undulation pump total artificial heart: 50 and 54 day survival periods with 1/R control

    Y Abe, T Chinzei, T Isoyama, S Kobayashi, T Ono, Saito, I, K Iwasaki, M Ishimaru, A Baba, A Kouno, T Ozeki, T Tohyama, K Imachi

    ASAIO JOURNAL   49 ( 3 ) 325 - 332  2003.05  [Refereed]

     View Summary

    The undulation pump total artificial heart (UPTAH) is a unique, implantable, total artificial heart (TAH) that uses undulation pumps. To achieve long-term survival in animals with physiologic hemodynamic conditions, a control method based on conductance and arterial pressure was applied to UPTAH. With this control method, called 1/R control, survival periods of 50 days (No. 0016, 49.6 kg) and 54 days (No. 0030, 42.5 kg) were obtained in adult female goats. In No. 0016, 1/R control was applied to the left pump, whereas in No. 0030, it was applied to the right pump. Another pump was used for left-right balance control. The control stability was better in No. 0030 than in No. 0016. The sucking effect of the left atrium was remarkable in No. 0016, possibly because of a time delay when left-right balance control was performed with the right pump. In No. 0016, the cause of death was probably a thrombus flown from a panus in the left atrium. It is possible that the left atrial suction effect influenced the thrombus and panus formation in the left atrium. In No. 0030, the cause of death was a small rupture of the membrane in the right pump. The rupture may have been caused by excessive negative pressure inside the pump. This pressure resulted from suction of the right atrium because of an unexpected control excursion, which was probably caused by a software bug. It will be necessary to redesign the undulation pump and improve the software to achieve longer survival periods for animals with physiologic hemodynamic conditions.

    DOI PubMed

  • Development of a polymer bileaflet valve to realize a low-cost pulsatile blood pump

    K Iwasaki, M Umezu, K Iijima, A Inoue, K Imachi, CX Ye

    ARTIFICIAL ORGANS   27 ( 1 ) 78 - 83  2003.01  [Refereed]

     View Summary

    The final goal of this study is to realize a low-cost pulsatile blood pump especially for patients with acute heart failure or postoperative low cardiac output syndrome. In support of the pump, two types of polymer bileaflet valves with different configuration of the valve seats were developed. Influence of the leaflet thickness on the hydrodynamics of the prototype was preliminarily investigated among 70 mum, 100 mum, and 150 mum. As to the valves with the thinner leaflets, buckling of the leaflets was observed, which induced a large amount of regurgitation at valve closure. However, by thickening the leaflet to 150 mum, the mean flow of the prototype and the second model could be successfully comparable to the Medtronic-Hall valve. Moreover, accelerated fatigue tests showed that reinforcement of the valve seat with the additional spokes in the second model extended the durability by four times as compared with the prototype, equivalent to an in vivo duration of over one month.

    DOI PubMed

  • 人工臓器のin vitro抗血栓性評価を目的とした完全大気非接触型拍動流試験回路の開発

    岩崎清隆, 梅津光生, 佐伯航, 石原一彦, 井街宏

    第15回バイオエンジニアリング講演会講演論文集     361 - 362  2003

  • 大動脈弁置換用を目指したブタ組織弁の脱細胞化手法の検討及びin vitro拍動下での細胞播種用バイオリアクターの開発

    岩崎清隆, 尾崎重之, 中澤剛, 今井裕一, 守本裕司, 石原雅之, 菊地眞, 梅津光生

    日本機械学会関東支部第9期総会講演会講演論文集     83 - 84  2003

  • Progress in the control system of the undulation pump total artificial heart

    Saito, I, T Chinzei, Y Abe, M Ishimaru, S Mochizuki, T Ono, T Isoyama, K Iwasaki, A Kouno, A Baba, T Ozeki, K Takiura, T Tohyama, H Nakagawa, K Imachi

    ARTIFICIAL ORGANS   27 ( 1 ) 27 - 33  2003.01  [Refereed]

     View Summary

    The undulation pump total artificial heart (UPTAH) is a small implantable total artificial heart. As the UPTAH generates outflow and inflow at the same time, control of the UPTAH is very difficult. Therefore suitable control methods specifically for the UPTAH should be established. Various motor control, left-right flow balance control, and physiological control methods were examined and tried for the UPTAH control in this study. The control system is divided into seven categories. It has a hierarchical structure and all control modes work at the same time. The UPTAH with the newly developed control method has been implanted into the chest cavities of 48 goats. Until now, six goats survived for more than one month, including 63 days in the longest case. The good condition of the UPTAH implanted animal could be maintained with the newly developed control scheme, consisting of the 1/R control and several other additional controls.

    DOI PubMed

  • A novel in vitro device to investigate a calcification mechanism on cardiovascular implants

    Iwasaki K, Umezu M, Imachi K

    6th Polish-Japanese symposium on bio-medical engineering     41 - 42  2003

  • Third model of the undulation pump total artificial heart

    Y Abe, T Chinzei, T Isoyama, T Ono, S Mochizuki, Saito, I, K Iwasaki, M Ishimaru, A Baba, A Kouno, T Ozeki, T Tohyama, K Imachi

    ASAIO JOURNAL   49 ( 1 ) 123 - 127  2003.01  [Refereed]

     View Summary

    The undulation pump is a small, continuous flow displacement type blood pump, and the undulation pump total artificial heart (UPTAH) is a unique, implantable total artificial heart based on this pump. To improve the durability of the UPTAH for investigating long-term pathophysiology with UPTAH, a third model (UPTAH3) has been developed. UPTAH3 was designed to separate the left and right undulation shafts and to be more durable. The undulation pumps were also redesigned. UPTAH3 was implemented with a diameter of 76 mm, width of 78 or 79 mm, total volume of 292 ml, and weight of 620 g. The priming volumes of the left and right pumps are 26 and 21 ml, respectively. The atrial cuffs and outflow cannulae were also redesigned for UPTAH3. The maximum output against an arterial pressure load of 100 mm Hg is about 11 L/min. The maximum pump efficiency is about 15% in the left pump and 18% in the right pump, giving a maximum total efficiency for both of about 11%. To date, UPTAH3 has been tested in 17 goats, and the longest survival period was 46 days. This third model will be useful for investigating pathophysiology with UPTAH.

    DOI PubMed

  • Development of a polymer bileaflet valve to realize a low-cost pulsatile blood pump

    K Iwasaki, M Umezu, K Iijima, A Inoue, K Imachi, CX Ye

    ARTIFICIAL ORGANS   27 ( 1 ) 78 - 83  2003.01

     View Summary

    The final goal of this study is to realize a low-cost pulsatile blood pump especially for patients with acute heart failure or postoperative low cardiac output syndrome. In support of the pump, two types of polymer bileaflet valves with different configuration of the valve seats were developed. Influence of the leaflet thickness on the hydrodynamics of the prototype was preliminarily investigated among 70 mum, 100 mum, and 150 mum. As to the valves with the thinner leaflets, buckling of the leaflets was observed, which induced a large amount of regurgitation at valve closure. However, by thickening the leaflet to 150 mum, the mean flow of the prototype and the second model could be successfully comparable to the Medtronic-Hall valve. Moreover, accelerated fatigue tests showed that reinforcement of the valve seat with the additional spokes in the second model extended the durability by four times as compared with the prototype, equivalent to an in vivo duration of over one month.

    DOI

  • The improved jellyfish valve: Durability enhancement with sufficient blood compatibility

    K Iwasaki, M Umezu, Y Abe, T Chinzei, T Isoyama, Saito, I, M Ishimaru, K Imachi

    ASAIO JOURNAL   48 ( 5 ) 532 - 537  2002.09  [Refereed]

     View Summary

    The Jellyfish Valve is one of the most promising polymer valves for artificial hearts. The present problems to be solved are 1) how to prevent a membrane fracture and 2) how to eliminate a calcification, because both of these problems were observed in experiments with goats after 312 days and 414 days of pumping. Finite element analysis demonstrated that mechanical tensile strain induced in the membrane at valve closure was clearly consistent with the fracture location as well as calcification area in in vivo experiments. Based on this finding, a new valve seat with an additional concentric ring 14 mm in diameter and 0.5 mm in width was finally developed. The maximum strain was dramatically reduced to 52% by the design improvement. Moreover, accelerated fatigue tests demonstrated that the improved valve was 10 times more durable as compared with the original valve, which was equivalent to an in vivo duration of 8.3 years. In animal experiments, including 31days and 46 days use in a total artificial heart (TAH), no thrombus was found despite the lack of anticoagulant or antiplatelet therapies. These results indicate that the improved Jellyfish Valve might be one of the most durable polymer valves, able to perform in artificial hearts for a long period of time.

    DOI PubMed

  • In vitro evaluating system for prosthetic heart valves in a case of the Jyros Valve

    Fujimoto T, Tsutsumi Y, Shiraishi Y, Iwasaki K, Yoshida M, Umezu M, J.Begg, J.Woodward

    Biocybernetics and Biomedical Engineering 2002   22 ( 4 ) 46 - 46  2002.09

  • Left Ventricle simulator for surgeons’support

    Umezu M, Arita M, Iwasaki K, Shiraishi Y, Tono S, Uchida K

    Biocybernetics and Biomedical Engineering 2002   22 ( 4 ) 47 - 53  2002.09

  • Implications for the establishment of accelerated fatigue test protocols for prosthetic heart valves

    K Iwasaki, M Umezu, K Iijima, K Imachi

    ARTIFICIAL ORGANS   26 ( 5 ) 420 - 429  2002.05  [Refereed]

     View Summary

    The goal of this research is to establish a reliable methodology for accelerated fatigue tests of prosthetic heart valves. A polymer valve was the subject, and the influence of various drive parameters on durability was investigated in three different machines. Valve lifetime was notably shortened by increasing the cyclic rate or stroke even though the maximum pressure difference at valve closure was maintained at 120 mm Hg. These results demonstrate that adjustment of the maximum transvalvular pressure is not sufficient to ensure tests are conducted under the same conditions and indicate that measurement of the dynamic load would be more efficacious. Moreover, the locations of tears sustained in the accelerated tests differed from those encountered in an animal experiment although in both cases the locations were entirely consistent with the areas of strain concentration revealed by finite element analysis. These findings should be discussed during a revision of ISO 5840.

    DOI PubMed

  • Spiral vortex ventricular assist device : Its history and present status

    Umezu M, Ye CX, Nugent A, Nakamura T, Iwasaki K, Arita M, Shiraishi Y, Tanaka T, Imachi K, Ishihara K, Chang V.P

    Proceedings 2nd Wasda-Renji Hospital BioMedical Engineering Symposium     6 - 7  2002.03

  • ブタ僧帽弁を組み込んだ手術支援シミュレータの開発—機械式循環モデルの有効活用例—

    岩崎清隆, 内田浩司, 有田誠, 加瀬川均, 梅津光生

    BME   16 ( 8 ) 20 - 27  2002

    DOI

  • Ripple reduction control of the undulation pump total artificial heart

    Saito, I, T Chinzei, S Mochizuki, Y Abe, T Isoyama, K Iwasaki, T Suzuki, T Karita, T Ono, A Kouno, M Ishimaru, A Baba, T Ozeki, T Tohyama, S Kobayashi, K Imachi

    ARTIFICIAL ORGANS   26 ( 1 ) 40 - 44  2002.01  [Refereed]

     View Summary

    An undulation pump total artificial heart (UPTAH) in which the revolutions of the motor are converted to undulation motion of a disk has been developed. In an experiment, a goat using the UPTAH survived for 54 days. However, a large ripple was observed in the device's output pressure and flow waveform. In calculating the spectrum of the ripple, we found that the ripple mainly comprised 2 frequency sine waves: 1 having the same frequency as and 1 having double the frequency of the motor revolutions. To reduce the ripple, 2 sine waves, 1 having the same frequency as and 1 having double the frequency of the motor revolutions. were provided to the motor current to modulate the pulse width of the pulse width modulation controlling the: motor revolutions. This ripple control method reduced the pressure ripple by 90% in a mock circulation and by 70% in animal experiments. These results revealed that the ripple generated in the UPTAH could be controlled through the use of motor control software.

    DOI PubMed

  • Biomedical Engineering approaches to evaluate a function of artificial organs

    Umezu M, Shiraishi Y, Iwasaki K, Arita M, Shimizu T, Okano T, Sakurai Y

    Proc. of the 11th International Conference on Biomedical Engineering    2002

  • An inexpensive pulsatile blood pump: Fabrication strategies and in vitro reliable methodology to evaluate blood compatibility

    Iwasaki K, Umezu M, Tsujimoto T, Yoshida K, Saeki W, Yi Q, Ishihara K, Imachi K, Sakurai Y

    Proc. of the 11th International Conference on Biomedical Engineering    2002

  • Spiral vortex ventricular assist device: Improvement by engineering analysis and simulation

    K Iwasaki, M Umezu, CX Ye, A Nugent, T Nakamura, M Arita, Q Yi, T Tanaka, K Imachi, K Ishihara, Chang, V

    SYSTEM SIMULATION AND SCIENTIFIC COMPUTING (SHANGHAI), VOLS I AND II     1035 - 1039  2002

     View Summary

    Development of an inexpensive artificial organs is one of the most important issues. The final goal of this research is to realize such a low-cost pulsatile blood pump, especially for use in acute congestive heart failure or postoperative low cardiac output syndrome. In this study, design of the pneumatically-driven Spiral Vortex (SV) pump, which was originally developed in Australia, Was adopted. The specific feature is low hemolysis, because a continuous spiral flow is generated inside the pump without any stagnation. First, for the purpose of establishing a mass production system, vacuum forming technique was employed for fabrication of the pump. Each quality-controlled pump could be manufactured in one hour including assembling process, corresponding 1/15 times as compared with that by conventional injection-molding and/or solution casting technique. Second, in order to achieve blood compatibility, a novel phospholipid polymer composed of 2 methacryloxyethyl phosphorylcoline (MPC) was coated on the whole internal surface of the pump. A preliminary comparative in vitro test exhibited a superior blood compatibility of the MPC-coated pump, as compared with the non-coated one. At this stage, the final design is under investigation by the use of computational fluid dynamics. Third, the polymer Jellyfish valve has been developed to realize a low-cost pulsatile blood pump. Comparison between finite element analysis and animal experimental results of the original Jellyfish Valve indicated that reduction of strain concentration in the leaflet would be of great benefit in a prevention of fracture and calcification, observed after 10 months in an animal experiment. Based on the findings, a new valve seat was designed aiming to effectively reduce the strain concentration. The modified valve was hydrodynamically comparable with the Medtronic-Hall valves, while durability of the modified one was dramatically extended over 10 times as compared with the original, that was equivalent to an in vivo duration of 8.3 years. Moreover, an excellent anti-thrombogenicity as well as anti-calcification was achieved throughout a 240 day animal experiment. The data above are encouraging to continue development of a clinical quality inexpensive SV ventricular assist system.

  • A challenge to develop an inexpensive "spiral vortex pump"

    T Tsujimoto, K Iwasaki, W Saeki, K Yoshida, M Arita, M Umezu, Y Qian, CX Ye, Kou, I, K Ishihara, T Tanaka

    SYSTEM SIMULATION AND SCIENTIFIC COMPUTING (SHANGHAI), VOLS I AND II     1040 - 1044  2002

     View Summary

    It is well known that the cost of artificial heart is more expensive than other cardiovascular devices and its cost still tends to increase. The cost is one of the important factors to be chosen by the doctors, patients and their families. Therefore, vacuum forming technique has been adopted to fabricate the spiral vortex pump to achieve lower fabrication cost. First of all, optimal conditions of vacuum fori-ning were investigated and it became possible to fabricate well quality components of the spiral vortex pump. Next, a polymer Jellyfish valve and Medtronic-Hall valve were incorporated into the spiral vortex pump to compare their hydrodynamic performance. At last, throughout the blood compatibility test, MPC coating exhibited a favorable effect to eliminate thrombus inside the pump. From the result of all, it was possible to fabricate a pulsatile blood pump at lower price and new method of closed circuit of blood compatibility method was useable in developing process of artificial heart.

  • ブタ僧帽弁を組み込んだ手術支援シミュレータ

    岩﨑清隆, 内田浩司, 有田誠, 加瀬川均, 梅津光生

    第15回日本ME学会秋季大会論文集     61 - 62  2001.11

  • Improvement of a polymer bileaflet valve to realize a low-price pulsatile blood pump

    Proceedings 3rd Japan-Australia Cardiovascular Bioengineering Symposium     29 - 30  2001.11

  • In vitro performance of “EVAHEART”

    Shiraishi Y, Saito Y, Moriyama H, Iwasaki K, Umezu M, Fujimoto T, Miyakoshi T, Kitano T, Tokuno T, Yamazaki K

    Proceedings 3rd Japan-Australia Cardiovascular Bioengineering Symposium     25 - 26  2001.11

  • Design improvement of the Jellyfish valve for long-term use in artificial hearts

    K Iwasaki, M Umezu, K Imachi, K Iijima, T Fujimoto

    INTERNATIONAL JOURNAL OF ARTIFICIAL ORGANS   24 ( 7 ) 463 - 469  2001.07

     View Summary

    In a previous communication, we reported a leaflet fracture in a Jellyfish valve that was incorporated into a blood pump, after a 312-day animal implant duration. Subsequent finite element analysis revealed that the fracture location was consistent with an area of maximum strain concentration. Therefore, the aim of this study was to improve the durability in the light of these findings. Based on the engineering analysis results, a new valve seat having a concentric ring, of 0.5-mm width, located at a radius of 7.0 mm, was designed and fabricated. Accelerated fatigue tests, conducted under the conditions recommended by ISO 5840, demonstrated that the durability of this new prototype was extended by a factor of 10, as compared to the original valve. Moreover, further finite element analysis indicated that the maximum equivalent elastic strain of the proposed new valve was reduced by 52.3% as compared to the original valve. Accordingly, it has been confirmed that the modified Jellyfish valve is suitable for use in long-term artificial hearts.

  • Extension of durability of jellyfish valve for lpng-term use in artificial hearts

    Iwasaki K, Unezu M, Imachi K, Abe Y, Chinzei T, Isoyama T, Saito I, Fujimoto T

    Journal of Congestive Heart and Circulatory Supphort(2001)   1 ( 4 ) 293 - 297  2001.06

  • A challenge to develop an Inexpensive spiral vortex pump

    Iwasaki K, Umezu M, Tsujimoto T, Saeki W, Inoue A, Nakazawa T, Arita M, Ye CX, Imachi K, Ishiwata K, Tanaka T

    Proceedings 2nd Wasda-Renji Hospital BioMedical Engineering Symposium     8 - 10  2001.03

  • A new hypothesis on the mechanism of calcification formed on a blood-contacted polymer surface

    K. Imachi, T. Chinzei, Y. Abe, K. Mabuchi, H. Matsuura, T. Karita, K. Iwasaki, S. Mochizuki, Y. P. Son, I. Saito, A. Kouno, T. Ono

    Journal of Artificial Organs   4 ( 1 ) 74 - 82  2001

     View Summary

    Calcification on a blood-contacting polymer surface in an artificial heart is one of the most serious problems. Recently, we maintained a goat with a total artificial heart (AH) for 532 days without systemic anticoagulation. Sac-type blood pumps coated with segmented polyurethane and incorporating jellyfish valves, thin polymer membrane valves, were used in the experiment. The pump was exchanged for a new one on the 312th day on the left side and the 414th day on the right side. They were analyzed with a scanning electron microscope (SEM) and an X-ray microanalyzer. The valve membrane after 312 days of pumping revealed plastic deformation expanding toward upstream between the spokes by creep fatigue with blood pressure difference when the valve closed. Calcification on the membrane was concentrated in the limited portions that received a strong stretching force: the upstream side of the membrane between the spokes and downstream side of the membrane on the spokes. Slight or no calcification was observed on the opposite side of the membrane that received a compression force, and no calcification was found on nonmoving parts such as the center of the membrane and spokes. A new hypothesis on the mechanism of calcification at the portion that received repeated stretching force was raised. The repeated stretching force would extend the polymer membrane, causing some loosening between polymer molecules and generating microgaps. The blood protein and phospholipid would invade into these microgaps, which would then attract Ca ions followed by phosphate ions to make their complexation. The hypothesis could well explain the calcification phenomena on a blood-contacting polymer surface, and gave a good clue on how to protect from calcification.

    DOI

  • Flow-transformed pulsatile total artificial heart using axial flow blood pump

    Isoyama T, Chinzei T, Abe Y, Ono T, Mochizuki S, Saito I, Ishimaru M, Iwasaki K, Baba A, Karita T, Ozeki T, Kouno A, Imachi K

    Journal of Congestive Heart Failure and Circulatory Support   1 ( 4 ) 327 - 330  2001

  • Miniature undulation pump for the study of renal circulation

    Saito I, Abe Y, Chinzei T, Ono T, Isoyama T, Mochizuki S, Iwasaki K, Kouno A, Karita T, Ishimaru M, Baba A, Imachi K

    Journal of Congestive Heart Failure and Circulatory Support   1 ( 4 ) 321 - 325  2001

  • Extension of durability of jellyfish valve for long-term use in artificial hearts

    Iwasaki K, Umezu M, Imachi K, Abe Y, Chinzei T, Isoyama T, Saito I, Fujimoto T

    Journal of Congestive Heart Failure and Circulatory Support   1 ( 4 ) 293 - 297  2001

  • Design of atrial cuff for the undulation pump total artificial heart

    Imachi K, Chinzei T, Abe Y, Isoyama T, Ono T, Mochizuki S, Saito I, Ishimaru M, Iwasaki K, Mama A, Karita T, Ozeki T, Kouno A

    Journal of Congestive Heart Failure and Circulatory Support   1 ( 4 ) 195 - 200  2001

  • Progress in the development of the undulation pump total artificial heart

    Abe Y, Chinzei T, Isoyama T, Ono T, Mochizuki S, Saito I, Iwasaki K, Ishimaru M, Baba A, Kouno A, Karita T, Baba K, Imachi K

    Journal of Congestive Heart Failure and Circulatory Support   1 ( 4 ) 167 - 170  2001

  • One month survival with the undulation pump total artificial heart in a goat

    Y Abe, T Chinzei, T Isoyama, T Ono, S Mochizuki, Saito, I, K Iwasaki, M Ishimaru, T Karita, A Kuono, K Baba, K Imachi

    ARTIFICIAL ORGANS   25 ( 1 ) 69 - 71  2001.01

     View Summary

    The undulation pump is a small continuous flow displacement-type blood pump. The undulation pump total artificial heart (UPTAH) is a unique implantable total artificial heart using undulation pumps. An adult female goat weighing 45.8 kg was used for implantation. The natural heart was replaced with the UPTAH under extracorporal circulation. The cardiac output (CO) was maintained to 100 ml/kg/min by controlling the right pump manually. To prevent lung edema, the left pump was controlled automatically to maintain the left atrial pressure below 20 mm Hg. The CO was maintained for 2 weeks. Thereafter, the CO gradually decreased. The goat suddenly died because of a brain stroke on the 31st postoperative day. At autopsy, the cavity of the left atrial cuff was almost occupied by the big pannus-like thrombus, which was thought to be the cause of death. Improvement of the atrial cuff is necessary to obtain longer survival and is being modified. No thrombus was found inside the pumps. However, temperature rise in a left motor was a problem. Improvement of the efficiency in a motor is necessary. Although many problems still remained, 1 month survival could be obtained with this unique implantable TAH using continuous flow displacement-type blood pumps.

    DOI

  • A new hypothesis on the mechanism of calcification formed on a blood-contacted polymer surface

    K. Imachi, T. Chinzei, Y. Abe, K. Mabuchi, H. Matsuura, T. Karita, K. Iwasaki, S. Mochizuki, Y. P. Son, I. Saito, A. Kouno, T. Ono

    Journal of Artificial Organs   4 ( 1 ) 74 - 82  2001

     View Summary

    Calcification on a blood-contacting polymer surface in an artificial heart is one of the most serious problems. Recently, we maintained a goat with a total artificial heart (AH) for 532 days without systemic anticoagulation. Sac-type blood pumps coated with segmented polyurethane and incorporating jellyfish valves, thin polymer membrane valves, were used in the experiment. The pump was exchanged for a new one on the 312th day on the left side and the 414th day on the right side. They were analyzed with a scanning electron microscope (SEM) and an X-ray microanalyzer. The valve membrane after 312 days of pumping revealed plastic deformation expanding toward upstream between the spokes by creep fatigue with blood pressure difference when the valve closed. Calcification on the membrane was concentrated in the limited portions that received a strong stretching force: the upstream side of the membrane between the spokes and downstream side of the membrane on the spokes. Slight or no calcification was observed on the opposite side of the membrane that received a compression force, and no calcification was found on nonmoving parts such as the center of the membrane and spokes. A new hypothesis on the mechanism of calcification at the portion that received repeated stretching force was raised. The repeated stretching force would extend the polymer membrane, causing some loosening between polymer molecules and generating microgaps. The blood protein and phospholipid would invade into these microgaps, which would then attract Ca ions followed by phosphate ions to make their complexation. The hypothesis could well explain the calcification phenomena on a blood-contacting polymer surface, and gave a good clue on how to protect from calcification.

    DOI

  • Method of ranking of heart valve characteristics at mitral position based on statistical model analysis

    Makoto Arita, Kiyotaka Iwasaki, Mitsuo Umezu, Masanori Yoshida, Tetsuo Fujimoto, Hisayoshi Suma, Tadashi Isomura

    Journal of Artificial Organs   4 ( 2 ) 131 - 137  2001

     View Summary

    The purpose of this study was to explore a valve selection criterion based on the impact force generated at valve closure, and to test a statistical mathematical model for comparing valve performance. The impact force generated at valve closure in the mitral position was measured continuously, using a load cell mounted in the left atrial section of a mock circulatory system. Eight clinical valves were tested. The data obtained from the in vitro test were subjected to multiregression analysis, to enable systematic comparison of the impact forces of these valves. Furthermore, class I quantification theory was applied to construct the statistical mathematical model. As a result, the following interaction effect was observed in the statistical model. (1) The impact force generated at valve closure had a lower value in valves of smaller diameter. (2) The ranking of 29-mm-diameter valves by impact force was different for the flow region. Under the physiological flow condition of 4-61/min, high impact forces were generated in all valves, in the order Björk-Shiley monostrut, ATS, St. Jude medical, CarboMedics. We consider that low impact force at valve closure is desirable, upon consideration of the influence on the annulus tissue at valve replacement. From these findings, the results of the multiregression analysis provide indications for choosing the optimal valve for patients with severe mitral insufficiency (MI).

    DOI

  • In vitro performance tests of a newly-developed bileaflet polymer valve

    Iwasaki K, Umezu M, Imachi H, Iijima K, Morita M, Ye CX

    10th International Conference On Biomedical Engineering     343 - 343  2000.12

  • Accelerated fatigue testing method for heart valves

    Umezu M, Iwasaki K, Imachi h

    10th International Conference On Biomedical Engineering     51 - 51  2000.12

  • Development of a miniature undulation pump for the distributed artificial heart

    Y Abe, T Ono, T Isoyama, S Mochizuki, K Iwasaki, T Chinzei, Saito, I, A Kouno, K Imachi

    ARTIFICIAL ORGANS   24 ( 8 ) 656 - 658  2000.08

     View Summary

    Research of the distributed artificial heart is important not only to acquire the means of individual organ perfusion but also to clarify the characteristics of the organ and the mechanism of blood distribution. To investigate the distributed artificial heart, the miniature undulation pump was developed. The outer diameter and the thickness of the developed pump were 38 mm and 11 mm. respectively. The priming volume of the pump was 3.2 ml. The total size including the motor unit was 38 mm in diameter and 32 mm in length. The total weight was 67.5 g. The total volume was 27.5 ml. The pump was driven with pulse width modulation by using a 1 chip motor controller. More than 5 L/min of continuous output could be obtained. The results showed that the developed miniature undulation pump system had enough performance for individual organ perfusion.

    DOI

  • Development of a miniature undulation pump for the distributed artificial heart

    Y Abe, T Ono, T Isoyama, S Mochizuki, K Iwasaki, T Chinzei, Saito, I, A Kouno, K Imachi

    ARTIFICIAL ORGANS   24 ( 8 ) 656 - 658  2000.08

     View Summary

    Research of the distributed artificial heart is important not only to acquire the means of individual organ perfusion but also to clarify the characteristics of the organ and the mechanism of blood distribution. To investigate the distributed artificial heart, the miniature undulation pump was developed. The outer diameter and the thickness of the developed pump were 38 mm and 11 mm. respectively. The priming volume of the pump was 3.2 ml. The total size including the motor unit was 38 mm in diameter and 32 mm in length. The total weight was 67.5 g. The total volume was 27.5 ml. The pump was driven with pulse width modulation by using a 1 chip motor controller. More than 5 L/min of continuous output could be obtained. The results showed that the developed miniature undulation pump system had enough performance for individual organ perfusion.

    DOI

  • 人工弁加速耐久試験のISO基準の拡張:高分子製人工弁への適用に関する検討

    岩﨑清隆, 梅津光生, 井街宏, 藤本哲男

    人工臓器   29 ( 2 ) 385 - 385  2000.03

    DOI

  • 高分子製人工弁の加速耐久試験確立に向けての力学的検討

    岩﨑清隆, 梅津光生, 井街宏, 藤本哲男

    人工臓器   29 ( 2 ) 489 - 489  2000.03

    DOI

  • 冠動脈ステントの力学的挙動試験

    梅津光生, 堀切芳一, 岩崎清隆, 藤本哲雄

    人工臓器   29 ( 1 ) 99 - 99  2000.02

    DOI

  • 高速ビデオカメラを用いた人工弁の回転に関する検討

    藤本哲男, 比留間信義, 堤祐一, 岩﨑清隆, 白石泰之, 梅津光生, John Begg, John Woodard

    人工臓器   29 ( 1 ) 117 - 117  2000.02

    DOI

  • 冠動脈ステントの力学的挙動試験

    梅津光生, 堀切芳一, 岩﨑清隆, 藤本哲男

    人工臓器   29 ( 1 ) 99 - 99  2000.02

    DOI

  • A step forward for the undulation pump total artificial heart

    Yusuke Abe, Tsuneo Chinzei, Takashi Isoyama, Toshiya Ono, Shuichi Mochizuki, Itsuro Saito, Kiyotaka Iwasaki, Mitsuhiko Ishimaru, Atsushi Baba, Akimasa Kouno, Toshinaga Ozeki, Takahiro Tohyama, Kazunori Baba, Kou Imachi

    Journal of Artificial Organs   3 ( 2 ) 70 - 74  2000

     View Summary

    In the University of Tokyo, various types of total artificial heart (TAH) have been studied. Based on the experiences of TAH research, the development of the undulation pump total artificial heart (UPTAH) started in 1994. The undulation pump is a small-size, continuous-flow, displacement-type blood pump, and the UPTAH is a unique implantable total artificial heart that uses the undulation pump. To date, three models of UPTAH have been developed. The first model, UPTAH1, was developed to investigate the possibility of reducing the size of the device so it could be implanted in small adults, such as Japanese patients, in 1994. The second model, UPTAH2, which was the prototype of the animal experimental model, was developed in 1996 to investigate the possibility of survival with the UPTAH. The third model, UPTAH3, which is the present model, was developed in 1998 to enable long-term survival in animal experiments and to investigate the pathophysiology of the UPTAH. From July 1996 to October 1999, 22 implantations of UPTAH2 or UPTAH3 were performed in goats. In spite of the limitation of their small chest cavity, the UPTAH could be implanted into the chest of all goats. Using UPTAH3, survival of 31 days could be obtained. The research and development of UPTAH are ongoing.

    DOI

  • A new approch for the improvement of accelerated fatigue testing methodology

    Iwasaki K, Umezu M, Kobayashi Y, Fujimoto T, Imachi K

    Proceedings of inaugural Japan-Australia cardiovascular bioengineering meeting     29 - 30  1999.05

  • Contribution of mechanical engineering to the field of artificial organs

    Umezu M, Fujimoto T, Shiraishi Y, Iwasaki K, Kohno K, Arita M

    Proceedings of inaugural Japan-Australia cardiovascular bioengineering meeting     2 - 3  1999.03

  • 人工弁5

    藤本 哲男, 岩崎 清隆, 松居 喜郎

    人工臓器   28 ( 4 ) s77 - s78  1999

    DOI CiNii

  • 耐久性向上を目指した高分子製人工心臓弁の開発とその総合的評価, ライフサポート

    岩﨑清隆

    ライフサポート   11 ( 2 ) 12 - 14  1999

    DOI

  • 耐久性向上を目指した高分子製人工心臓弁の開発とその総合的評価

    岩﨑清隆

    ライフサポート   11 ( 2 ) 12 - 14  1999

    DOI

  • Three types pf in vitro evaluation test system for blood pump performance

    Umezu M, Fujimoto T, Shiraishi Y, Iwasaki K, Zhonggang Feng

    ICBME/ISBMRE/JCCCAS’98, 第8回コンピュータ支援画像診断学会大会,第7回日本コンピュータ外科学会大会     1 - 2  1998.09

  • 人工心臓<人工心臓用弁ほか>

    富永 隆治, 岩崎 清隆, MORSI Yos S., 田山 栄基, 大塚 吾郎, 田山 栄基, 大塚 吾郎

    人工臓器   27 ( 4 ) S39 - S41  1998

    DOI CiNii

  • 有限要素法を用いたひずみ解析によるJellyfish弁のカルシウム沈着発生位置の検討

    岩﨑清隆, 梅津光生, 藤本哲男, 井街宏

    人工臓器   27 ( 2 ) 545 - 550  1998

    DOI

  • Improvement of dynamic conditions in the accelerated fatigue testing for prosthetic heart valves

    Iwasaki K, Umezu M, Wakui H, Kawada H, Fujimoto T, Imachi K

    Proc. of the 9th International Conference on Biomedical Engineering     342 - 344  1997

  • Improvement of dynamic conditions in the accelerated fatigue testing for prosthetic heart valves

    Iwasaki K, Umezu M, Wakui H, Kawada H, Fujimoto T, Imachi K

    9th international conference on biomedical engineering     342 - 345  1997

  • 冠動脈ステントの力学的挙動試験

    梅津光生, 堀切芳一, 岩﨑清隆, 藤本哲男

    人工臓器   29 ( 1 ) 99 - 104

    DOI

  • Regional myocardial behaviour cardiac surface under arrhythmic conditions

    Uematsu M, Shiraishi Y, Sekine K, Yambe T, Saijo Y, Ando H, Park Y, Takeda S, Iwasaki K, Umezu M

    Proceedings of 12th International Conference on Biomedical Engineering   12   1A5 - 05

  • 医工融合に基づく先進医療研究の展開

    岩﨑清隆, 梅津光生

    可視化情報   30 ( 1 ) 3 - 6

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Books and Other Publications

  • 体内で組織再構築し自己組織化する新しい価値を生む膝前十字靭帯再建治療機器;医用工学ハンドブック(監修;佐久間一郎;秋吉一成;津本浩平)

    岩﨑清隆(pp.417-424)

    NTS  2022.02

  • 冠動脈ステントの効果的治療法と研究開発を促進する新規評価法;医用工学ハンドブック(監修;佐久間一郎;秋吉一成;津本浩平)

    岩﨑清隆(pp.368-378)

    NTS  2022.02

  • 基礎工学から;流体解析から得られる理想的分岐部ステント治療とは;Coronary Intervention

    岩﨑清隆(pp. 10-14)

    メディアルファ社  2021.03

  • 膝前十字靭帯損傷の治療に用いる脱細胞化腱;監修;岸田晶夫;山岡哲二;干場隆志

    岩﨑清隆, 伊藤匡史(pp.205-212)

    シーエムシー出版  2019.03

  • One-point advice;Experimental comparison;between the reimplantation method;remodeling method;Aortic Valve Preservation;Concepts a;Approaches

    K. Sasaki, K. Iwasaki(pp. 123-126)

    Springer Singapore  2019

  • 血液適合性評価法の開発、バイオテクノロジーシリーズ

    植松美幸, 宮島敦子, 野村祐介, 蓜島由二, 伊佐間和郎, 岩崎清隆, 梅津光生(pp.26-40)

    シーエムシ―出版・医療用バイオマテリアルの研究開発  2017.02

  • 脱細胞化組織を用いた腱索機能を有する人工僧帽弁の開発, バイオ・医療への3Dプリンティング技術の開発最前線

    岩崎清隆, 村真人(pp. 162-166)

    シーエムシー・リサーチ  2016.12

  • eimplantation法とremodeling法の比較、実験,大動脈弁形成術のすべて

    佐々木健一, 岩崎 清隆, 國原孝, 高梨秀一郎(pp. 66-68)

    文光堂  2015

  • 医療機器・材料の血液適合性評価と,生体外(in vitro)で可能な評価手法の展望, 生体適合性制御と要求特性掌握から実践する高分子バイオマテリアルの設計・開発戦略

    岩崎 清隆(pp. 247-258)

    サイエンス&テクノロジー  2014.05

  • A proposal for redesigning aortofemoral prosthetic Y graft for treating abdominal aortic aneurysms, Aortic aneurysm recent advances

    T. Fujimoto, H. Iwamura, Y. Shiraishi, T. Yambe, K. Iwasaki, M. Umezu

    2013.04

  • 理工学の立場からの医工学人材育成

    岩﨑清隆, 梅津光生

    Biophilia  2013

  • 先端医療シリーズ43 循環器疾患の最新医療 人工心臓弁

    岩﨑清隆

    寺田国際事務所/先端医療技術研究所  2012.10

  • 拍動循環バイオリアクター:動脈血管の創生、再生医療のための培養システム

    岩﨑清隆

    CMC出版  2010.01

  • 人工臓器の非臨床性能評価法の開発

    岩﨑清隆

    2008.07

  • 心臓弁の再生—体内で自己細胞により再生・自己化を誘導する無細胞化心臓弁の創生—

    岩﨑清隆

    再生医療技術の最前線・CMC出版  2007.05

  • 再生医療、生命・医療・福祉ハンドブック

    岩﨑清隆

    2007.02

  • 人工弁、生命・医療・福祉ハンドブック

    岩﨑清隆

    コロナ社  2007.02

  • 人工臓器で幸せですか?(梅津光生編)『心臓弁膜症と治療』

    岩﨑清隆

    コロナ社  2005.10

  • Artificial Heart: Heart Replacement 7, eds. By T.Akutsu and Koyanagi H

    K. Iwasaki, M. Umezu, K. Imachi, Y. Abe, T. Chinzei, T. Isoyama, I. Sato, T. Fujimoto

    Isis Medical Media Limited  2001

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Misc

▼display all

Awards

  • 令和3年度 科学技術分野の文部科学大臣表彰 科学技術賞(研究部門)

    2020   革新的循環型非臨床試験系によるクラスIV治療機器開発の研究

  • 2020年度日本機械学会標準事業表彰

    2020   先進的治療機器の有効性と安全性評価のための実臨床を模した非臨床試験機器と評価法の開発

  • ARIA INNOVATION AWARD 2018

    2018  

  • 2013 Best Abstract Award

    2013   TCTAP (Transcatheter Cardiovascular Therapeutics Asia Pacific Conference)   "Flexibiity and Stent Fracture Potensials Against Cyclically Bending Coronary Artery Motion: Comparison Between 2-Link and 3-Link DESs"

  • Outstanding Paper Award

    2008   "Successful reproduction of In-Vitro fracture of an endovascular stent in superficial femoral artery utilizing a novel multi-loading durability test system"

  • 第10回早稲田ベンチャーフォーラム最優秀賞

    2007   無細胞化組織の事業化プラン

  • 各ステントの構造の違いがもたらす留置後のステント形状の検討

    2007  

  • 12th International Conference on Biomedical Engineering, Outstanding Paper Award受賞

    2005  

  • 第31回人工心臓と補助循環懇話会若手研究奨励賞

    2003  

  • 第41回日本人工臓器学会オリジナル賞受賞

    2003  

  • 第47回アメリカ人工臓器学会ASAIO Fellowship Award

    2001  

  • 第38回日本人工臓器学会オリジナル賞(阿部裕輔らと)

    2000  

  • ライフサポート学会研究奨励賞

    1999  

▼display all

Research Projects

  • 治験実施に向けた膝前十字靭帯再建術に用いる脱細胞化動物組織由来の医療機器の開発

    日本医療研究開発機構  医工連携事業化推進事業

    Project Year :

    2019.04
    -
    2022.03
     

    岩﨑清隆

  • 脱細胞化組織を用いた膝前十字靭帯再建大動物実験による生体内靭帯化に関する研究

    文部科学省  科学研究費 基盤研究(B)

    Project Year :

    2017.04
    -
    2020.03
     

    岩崎 清隆

  • 革新的医療機器の先進的非臨床試験法に関するガイドライン

    厚生労働省  革新的医療機器等国際標準獲得推進促進事業

    Project Year :

    2017.04
    -
    2020.03
     

    岩崎 清隆

  • 不具合情報の効率的解析手法に関する研究

    日本医療研究開発機構  医薬品等規制調和・評価研究事業

    Project Year :

    2017.04
    -
    2019.03
     

    岩崎 清隆

  • 高強度NiTiを用いた下肢用セルフエキスパンダブルステントの開発・海外展開

    日本医療研究開発機構  医工連携事業化推進事業

    Project Year :

    2016.04
    -
    2018.03
     

    岩崎 清隆

  • 医療機器の安全対策充実のためのリスク・ベネフィット評価のフレームワーク構築に関する研究

    日本医療研究開発機構  医薬品等規制調和・評価研究事業

    Project Year :

    2016.04
    -
    2018.03
     

    岩崎 清隆

  • 植込み型医療機器の最適な使用成績評価期間の設定方法に関する研究

    日本医療研究開発機構  医薬品等規制調和・評価研究事業

    Project Year :

    2015.04
    -
    2018.03
     

    岩崎 清隆

  • 革新的医療機器の開発を加速する性能試験法拡充のための研究

    日本医療研究開発機構  医薬品等規制調和・評価研究事業

    Project Year :

    2015.04
    -
    2018.03
     

    岩崎 清隆

  • 大動脈ステントグラフトを用いた治療目標達成度を評価する拍動流シミュレータ開発

    文部科学省  科学研究費 挑戦的萌芽

    Project Year :

    2015.04
    -
    2017.03
     

    岩崎 清隆

  • 無細胞化技術と生体組織滅菌技術による自己組織化する前十字靭帯再建デバイスの開発

    文部科学省  科学研究費 基盤研究(B)

    Project Year :

    2014.04
    -
    2017.03
     

    岩崎 清隆

  • 前十字靭帯再建手術に用いる動物由来無細胞化腱の事業化

    文部科学省  イノベーションシステム整備事業大学発新産業創出拠点プロジェクト(プロジェクト支援型)

    Project Year :

    2014.04
    -
    2017.03
     

    岩崎 清隆

  • 抗血栓性評価の新展開

    文部科学省  科学研究費 挑戦的萌芽

    Project Year :

    2012.04
    -
    2014.03
     

    岩崎 清隆

  • 自己治癒能力を引き出す無細胞化組織実用化のための総合的基礎研究

    文部科学省  基盤研究(B)

    Project Year :

    2012.04
    -
    2014.03
     

    岩崎 清隆

  • 自己治癒能力を引き出す再生促進型滅菌済無細胞腱:無細胞ウシ腱を用いたラット前十字靭帯再建実験による再生・安定性評価

    国立研究開発法人 科学技術振興機構  研究成果最適展開支援プログラムA-STEP FSステージ探索タイプ

    Project Year :

    2011.04
    -
    2012.03
     

    岩崎 清隆

  • 大動脈ステントグラフトを用いた治療目標達成度を評価する拍動流シミュレータ開発

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(挑戦的萌芽研究)

  • 1ヶ月保証の超低価格血液ポンプの実用化を阻む要素の徹低解明

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(萌芽研究)

  • Establishment of support technology for the development of surgical training simulator

  • 信頼性の高い抗血栓性評価方法の提案:完全大気非接触型拍動流循環回路の開発

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(若手研究(B))

  • Development of evaluation system for artificial organs from the viewpoints of clinical study, engineering, and statistics.

  • Flow field analysis of the flow around and inside the valsalva and of the coronary flow influenced by the prosthetic aortic valve

  • 生体血液循環を代替する拍動バイオリアクターによる強度を有する再生大動脈弁の開発

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(若手研究(B))

  • The research and development of durable decellularized aortic valves in collaboration with engineers.

  • Mechanical stimulation-induced vascular elastogenesis

  • Developement of a new stentless mitral valve for clinical application

  • 無細胞化技術と生体組織滅菌技術による自己組織化する前十字靭帯再建デバイスの開発

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(B))

  • 生物学をベースとした骨格系運動生理モデルの構築と医療応用

    文部科学省 

▼display all

Presentations

  • 脱細胞化組織を用いた靭帯再建の現状と展望

    岩崎 清隆

    第21回日本再生医療学会総会 

    Presentation date: 2022.03

  • Unrelenting challenge to create future of clinical treatment through Biomedical Engineering

    Kiyotaka Iwasaki

    第86回日本循環器学会学術集会 

    Presentation date: 2022.03

  • 新しい人工臓器開発に向けて:レギュラトリーサイエンス委員会/医療産業促進委員会の取り組み

    岩﨑清隆

    日本人工臓器学会大会 

    Presentation date: 2021.11

  • 人を模した非臨床試験の研究開発による治療機器の研究開発・事業化促進

    岩﨑清隆

    第59回日本人工臓器学会大会 

    Presentation date: 2021.11

  • LMT Bifurcationモデルを用いた新たな血栓性試験法の開発

    岩﨑清隆

    ARIA21 

    Presentation date: 2021.11

  • 医工・産学協働で治療機器開発

    岩﨑清隆

    ARIA;TWIns 合同企画 

    Presentation date: 2021.11

  • 組織脱細胞化技術を基盤とした生体内組織再構築

    岩﨑清隆

    日本機械学会 第33回バイオエンジニアリング講演会 

    Presentation date: 2021.06

  • 組織再生バイオマテリアル-脱細胞化生体組織-の最前線 靭帯の再生

    岩崎清隆, 伊藤匡史, 今井伸哉, 畑中淳, 権美旋, 内山晃大, 伊藤淳哉, 岡崎賢, 梅津光生

    第20回日本再生医療学会総会 

    Presentation date: 2021.03

  • Flow from entry and re-entry tears in chronic type B aortic dissection

    K. Iwasaki

    第48回日本血管外科学会 

    Presentation date: 2020.11

  • レギュラトリーサイエンス:先進的医療機器の迅速な実用化と安全な普及を促進する非臨床試験法の開発

    岩﨑清隆

    日本人工臓器学会教育セミナー 

    Presentation date: 2020.11

  • TWInsの今: 医工学研究の進展

    岩崎清隆

    Alliance for Revolution;Interventional Cardiology Advancement 2020 

    Presentation date: 2020.11

  • レギュラトリーサイエンス;医療をより良くする医療機器の実用化に向けて

    岩﨑清隆

    第36回日本人工臓器学会教育セミナー 

    Presentation date: 2020.03

  • 医療機器開発;効果的使用法の基盤となる非臨床試験の開発とTWIns共同大学院の取り組み

    岩﨑清隆

    ARIA2019 

    Presentation date: 2019.11

  • Patient-data based experimental simulator for developing and investigating effective use of transcatheter aortic valvevvvv

    K. Iwasaki

    IFAO2019 

    Presentation date: 2019.11

  • 先進的医療機器の効率的開発を促進する患者を模した非臨床試験系の開発

    岩﨑清隆, 松橋祐輝, 坪子侑佑, 朱暁冬, 高田淳平, 笠貫宏, 梅津光生

    第58回日本生体医工学会大会 

    Presentation date: 2019.06

  • ヒツジ膝前十字靭帯再建実験による脱細胞化腱の生体内組織再生の評価

    岩﨑清隆

    第45回日本臨床バイオメカニクス学会 

    Presentation date: 2018.11

  • 屈曲運動する病変;左主幹部でのOrsiroステントの性能;医工学評価

    岩﨑清隆

    第32回日本冠疾患学会 

    Presentation date: 2018.11

  • 実臨床を模した先進的非臨床試験法の開発と活用

    岩﨑清隆, 山崎健二, 加瀬川均, 松橋祐輝, 高田淳平, 朱暁冬, 梅津光生

    第56回日本人工臓器学会大会 

    Presentation date: 2018.11

  • 脱細胞化腱を用いたヒツジ膝前十字靭帯再建実験による生体内組織再生に関する評価

    岩﨑清隆, 伊藤匡史, 奥田慶也, 岡村昭慶, 八木優大, 江虹暁, 井桝浩貴, 高野和也, 岡崎賢, 梅津光生

    第56回日本人工臓器学会大会 

    Presentation date: 2018.11

  • Development of a clinically-relevant thrombogenicity testing method of an inflow cannula at the interface with left ventricle: Contribution to the approval of titanium-mesh in flow cannula of EVAHEART without clinical trial

    K. Iwasaki, K. Yamazaki, Y. Matsuhashi, A. Takahashi, M. Hirata, M. Umezu

    26th Annual Meeting of the International Society for Mechanical Circulatory Support (ISMCS2018) 

    Presentation date: 2018.11

  • 心膜の力学的特性;患者の年齢と採取部位が力学特性に与える影響に関する研究

    岩﨑清隆, 金一, 井桝浩貴, 加瀬川均, 高梨秀一郎, 梅津光生

    第7回ステントレス僧帽弁臨床研究会学術集会 

    Presentation date: 2018.09

  • 患者のための循環器工学の進展;現在そして未来へ;回日本心血管インターベンション治療学術集会

    岩﨑清隆

    CIVIT 2018 

    Presentation date: 2018.08

  • 開発における非臨床試験の役割と可能性;その限界について

    岩﨑清隆

    第2回 実践に基づく医療イノベーション研究会 

    Presentation date: 2018.06

  • 先進的非臨床試験法開発と国際標準化;グローバル展開

    岩﨑清隆, 松橋祐輝, 坪子侑佑, 朱暁冬, 笠貫宏, 梅津光生

    第57回日本生体医工学会大会 

    Presentation date: 2018.06

  • 脱細胞化腱を用いたヒツジ膝前十字靭帯による生体内での細胞浸潤の評価

    岩﨑清隆, 伊藤匡史, 井枡浩貴, 高野和也, 岡村昭慶, 奥田慶也, 八木優大, 吉本伸之, 梅津光生

    第32回日本整形外科学会 

    Presentation date: 2017.10

  • 3 times kissing balloon technique

    K. Iwasaki, Y. Hikichi

    European Bifurcation Club 2017 

    Presentation date: 2017.10

  • 持続的血液濾過器の血栓性評価in;vitro試験法の提案

    岩﨑清隆

    第28回日本急性血液浄化学会学術集会 

    Presentation date: 2017.09

  • 流体力学からみ;分岐部病変

    岩﨑清隆

    第26回 日本心血管インターベンション治療学会学術集会 

    Presentation date: 2017.07

  • 脱細胞化組織を用いたヒツジ膝前十字靭帯再建実験による生体内での細胞浸潤に関する検討

    岩﨑清隆, 伊藤匡史, 井枡浩貴, 高野和也, 岡村昭慶, 奥田慶也, 八木優大, 梅津光生

    第40回日本バイオレオロジー学会 

    Presentation date: 2017.05

  • 先進的医療機器開発の迅速化とリスクマネジメントを促進する非臨床評価法の開発意義と展望

    岩﨑清隆, 笠貫宏, 梅津光生

    第54回日本人工臓器学会大会 

    Presentation date: 2016.11

  • 膝前十字靱帯再建術に用いる無細胞化靱帯組織の開発

    岩﨑清隆, 伊藤匡史, 井枡浩貴, 高野和也, 岡村昭慶, 奥田慶也, 吉本伸之, 加藤義治, 梅津光生

    第54回日本人工臓器学会大会 

    Presentation date: 2016.11

  • Flow after stenting at left main bifurcation

    K. Iwasaki, Y. Hikichi

    European Bifurcation Club Meeting, Rotterdam 

    Presentation date: 2016.10

  • 膝前十字靭帯再建に用いる動物由来脱細胞化靭帯組織の開発;ヒツジ膝前十字靭帯再建による安定性と強度評価

    岩﨑清隆, 伊藤匡史, 井桝浩貴, 岡村昭慶, 高野和也, 奥田慶也, 吉本伸之, 加藤義治, 梅津光生

    第43回日本臨床バイオメカニクス学会 

    Presentation date: 2016.10

  • 膝前十字靭帯再建に用いる脱細胞化ウシ腱の開発;ラット膝前十字靭帯再建による再生能と炎症反応評価

    岩﨑清隆, 伊藤匡史, 高野和也, 井桝浩貴, 奥田慶也, 岡村昭慶, 吉本伸之, 加藤義治, 梅津光生

    第43回日本臨床バイオメカニクス学会 

    Presentation date: 2016.10

  • ヒト左心室モデルを有する拍動循環シミュレータを用いたNormo弁の拍動動態に関する研究

    岩﨑清隆, 加瀬川均, 臼井一晃, 高田淳平, 朱暁冬, 梅津光生

    第5回ステントレス僧帽弁臨床研究会学術集会 

    Presentation date: 2016.09

  • 革新的医療機器実用化促進のための非臨床性能評価系と評価法の確立;Engineering Based Medicine

    岩﨑清隆

    第6回 レギュラトリーサイエンス学会学術総会 

    Presentation date: 2016.09

  • 無細胞化腱を用いた異種動物の前十字靭帯再建による再性能評価

    Presentation date: 2016.06

  • 革新的医療機器実現化のためのEngineering Based Medicineに基づく非臨床性能評価系と評価法の開発

    Presentation date: 2016.01

  • 滅菌済無細胞化ウシ腱を用いたラット膝前十字靭帯再建による再生能と炎症反応評価

    Presentation date: 2015.11

  • 先進的人工弁・弁膜治療法の実用化と安全な普及を加速する非臨床評価試験法の開発

    Presentation date: 2015.11

  • Novel insigts from flow visualization in the bench

    K. Iwasaki, Y. Hikichi

    11th European Bifurcation Club Meeting 

    Presentation date: 2015.09

  • 左心補助人工心臓の耐久試験法:日本初補助人工心臓の非臨床評価において留意した点

    Presentation date: 2015.09

  • 先進的医療機器の迅速な実用化と安全な普及を促進する非臨床評価試験法の進展

    Presentation date: 2015.09

  • 冠動脈分岐部でのステント不完全圧着と血流~先進的な非臨床試験からの洞察~

    Presentation date: 2015.07

  • 有限要素解析を用いた繰り返し屈曲下での冠動脈ステントの疲労破断予測

    Presentation date: 2015.05

  • Angulation range of coronary artery during the cardiac cycles is a key;factor inducing;stent;fracture;Demonstration by;an;i;i;ro accelerated durability test

    Iwasaki, J. Arai, T. Ohba, H. Tokutake, Z. Xiaodong, M. Umezu

    American Heart;Association Scientific Sessions;Circulation 

    Presentation date: 2014.11

  • 先進医療機器開発と普及のための医工学的非臨床評価法の進展

    Presentation date: 2014.11

  • 体組織無細胞化技術と組織滅菌技術による膝前十字靭帯再建デバイスの開発

    Presentation date: 2014.10

  • 下肢ステントと血管に生じる力学的負荷環境

    Presentation date: 2014.10

  • Stent!!〜冠動脈から抹消まで〜

    Presentation date: 2014.08

  • 先端医療機器・治療法の開発と普及のための非臨床評価の進展

    Presentation date: 2014.08

  • The Ultimate DES has Arrived 〜PREMIER® Performance〜

    Presentation date: 2014.07

  • 最先端医療機器の開発における医用工学

    Presentation date: 2014.04

  • 最先端医療機器の開発における医用工学

    Presentation date: 2014.04

  • 循環器医工学〜ステント性能評価法の進展〜

    Presentation date: 2014.04

  • ステントの特性

    Presentation date: 2014.03

  • EVAHEART脱血管改良による血栓症リスク低減評価のための血栓飛散量評価試験法の開発

    Presentation date: 2014.03

  • 新規In vitro 血栓評価法による補助人工心臓の平滑及びメッシュ脱血管周囲に形成される血栓の飛散リスク比較評価

    Presentation date: 2014.01

  • Fracture potentials and dynamic flexibility of peripheral stents: Insights into clinical practice from durability tests simulating multi-loaing environments of superficial femoral and popliteal arteries

    Presentation date: 2013.11

  • Comparison of flexibility and stent fracture potentials against cyclically bending coronary artery motions between2-link and 3-link DES

    Presentation date: 2013.05

  • Flexibility and Stent Fracture Potensials Against Cyclically Bending Coronary Artery Motion: Comparison Between 2-Link and 3-Link DESs

    Presentation date: 2013.04

  • 医療機器の非臨床評価

    Presentation date: 2013.01

  • Bending flexibility of Stents: Comparison among four different DES platforms with different design and materials deployed in in-vivo simulated cyclically-bending coronary artery model

    Presentation date: 2012.11

  • 人工臓器の溶血試験評価−再現性のある試験法−

    Presentation date: 2012.11

  • Decellularized and sterilized xenogeneic tissues inhibit complement and neutrophil activation: In vitro investigation using a novel blood-compatibility screening system

    Presentation date: 2012.09

  • ヒト鮮血を用いた無細胞化処理及び滅菌した動物由来組織の非臨床超急性免疫反応評価

    Presentation date: 2012.06

  • レギュラトリーサイエンスにおける評価科学で重要なこ と

    Presentation date: 2012.05

  • Neointimal coverage reduses a potential risk of stent separation of sirolimus eluting stent: Accelerated durability tests under in-vivo simulated cyclically-bended proximal right coronary artery environment

    Presentation date: 2011.11

  • ヒト前十字靱帯再建に適用可能なサイズの無細胞化ウシ腱の開発と力学的特性の検 討

    Presentation date: 2011.10

  • A novel in-vitro immune-response screening system?: Assessment of human blood response to decellularized, freeze-dried, and sterilized xenogeneic tissues

    Presentation date: 2011.08

  • ヒト血液性状を保持した超急性免疫反応評価実験システムの開発と無細胞組織の補体活性の評価

    Presentation date: 2011.06

  • 梅津光生,ヒト血液性状を保持した超急性免疫反応評価実験システムの開発と無細胞組織の補体活性の評価

    Presentation date: 2011.06

  • 治療機器開発に貢献する機械工学技術

    Presentation date: 2011.01

  • Development of in vitro test system to assess hyperacute immune response to decellularized bovine pericardium using human donor blood

    Presentation date: 2010.12

  • ヒト血液と無細胞化組織の超急性免疫反応評価実験系の開発

    Presentation date: 2010.11

  • Two stenting at coronary artery bifurcation yields show-flow region at carina :In vitro pulsatile flow investigation using elastic 3-dimensional stenotic bifurcated artery replica

    Presentation date: 2010.11

  • Fracture Potentials of Five Drug-Eluting-Stent Platforms in Proximal Right Coronary Artery Replica Under in-vivo Simulated Cyclically-Bended Environment

    Presentation date: 2010.03

  • 心臓の収縮・拡張に伴うヒト右冠動脈基部の屈曲変形環境下での5種類のステントの破損に関する加速耐久試験

    Presentation date: 2010.01

  • 組織無細胞化処理が心臓弁を構成する弁葉・血管壁・バルサルバ洞の細胞外マトリクス成分に及ぼす影響の検討

    Presentation date: 2010.01

  • Construction of elastic bifurcation model with stenosis for stent performance test

    Presentation date: 2010.01

  • ステント性能の実際:実臨床を踏まえたin vitro実験法開発の現状

    Presentation date: 2009.12

  • Recent Advance of Biomechanical Technology for Artificial Organs and Tissue Engineering

    Presentation date: 2009.11

  • 人工心臓を駆使した組織無細胞化技術による大動脈弁の再生と抗石灰化

    Presentation date: 2009.11

  • Repeated 3-times-balloon-inflation for stent deployment increases luminal patency of cobalt alloy stent: in vitro investigation using 75% stenotic mechanically-equivalent coronary artery replica

    Presentation date: 2009.11

  • 人工臓器の非臨床性能評価法の開発-現況とTWInsでの展開-

    Presentation date: 2009.10

  • Decellularized bovine ligaments using microwave irradiation and pulsatile detergent-circulation

    Presentation date: 2009.09

  • 医工融合研究に基づく冠動脈ステントの3回拡張法の提案

    Presentation date: 2009.08

  • Decellularized porcine aortic heart valve: Regeneration and calcification-prevention in one-year implantation in porcine descending aorta

    Presentation date: 2009.08

  • Biomechanical Investigation on optimal sterilization of decellularized pericardium

    Presentation date: 2009.08

  • ステントに関する医工融合研究 破断と拡張実験

    Presentation date: 2009.07

  • 工学的側面から覗いたStentの実際

    Presentation date: 2009.06

  • 医工融合による再生する心臓弁・小口径動脈血管の開発

    Presentation date: 2009.06

  • 再生・成長する大動脈弁の開発

    Presentation date: 2009.06

  • Flow Study at Bifurcation

    Presentation date: 2009.05

  • 冠動脈ステントプラットフォームに関する医工融合研究,各種DES のフラクチャー耐久性試験及びEndeavor ステント至適留置方法の考察

    Presentation date: 2009.05

  • 医工融合による再生医療技術の開発〜先端生命医科学センターでの取り組み〜

    Presentation date: 2009.03

  • 血漿タンパク質程度の大きさの表面粗さが抗血栓性に及ぼす影響

    Presentation date: 2009.02

  • 機械工学と医学の融合による再生組織開発への挑戦

    Presentation date: 2009.02

  • Tissue engineered small-diametaer blood vessel for coronary artery bypass grafting

    Presentation date: 2008.12

  • Successful reproduction on in-vivo fracture of an endovascular stent in superficial femoral artery utilizing a novel multi-loading durability test system

    Presentation date: 2008.12

  • Successful reproduction on in-vivo fracture of an endovascular stent in superficial femoral artery utilizing a novel multi- loading durability test system

    Presentation date: 2008.12

  • A novel multi-loading accelerated durability test system for peripheral vascular stents

    Presentation date: 2008.07

  • Tissue engineering artery utilizing the physiologic pulsatile bioreactor

    Presentation date: 2008.07

  • The novel decellularized bovine medial collateral ligaments for regenerative medicine,6th International Conference of The International Society for Gerontechnology

    Presentation date: 2008.06

  • 人工臓器開発の経験を駆使した再生医療基盤技術の開発

    Presentation date: 2008.03

  • A Robust Artery Engineered Using the Novel Pulsatile Pressure and Flow Bioreactor Sustem Controllable of Favorable Gas Concentration

    Presentation date: 2007.12

  • Tissue Engineered Three-layered Artery Using Hemodynamically-equivalent Pulsatile Bioreactor

    Presentation date: 2007.10

  • In vitro quantitative assessment of thrombogenicity of a pulsatile ventricular assist device using the original circulation system

    Presentation date: 2007.10

  • In vitro quantitative assessment of thrombogenicity of a pulsatile ventricular assist device using the original circulation system

    Presentation date: 2007.10

  • 独自の組織無細胞化技術による体内で再生・自己化を促す心臓弁及び血管の創生

    Presentation date: 2007.03

  • 生体内に酷似したバイオリアクターシステムによる強度のある3層血管の創生

    Presentation date: 2006.11

  • マイクロ波と拍動循環を駆使した無細胞化技術による再生促進型大動脈弁

    Presentation date: 2006.11

  • マイクロ波と拍動循環を駆使した無細胞化技術による再生促進型大動脈弁

    Presentation date: 2006.11

  • 末梢ステントの加速耐久試験装置の開発〜短期間で長期の有用性を予測する技術〜

    Presentation date: 2006.06

  • 末梢ステントの加速耐久試験 装置の開発〜短期間で長期の有用性を予測する技術〜

    Presentation date: 2006.06

  • Innovative bioreactor technologies produced a completely decellularized and pre-endothelialized functional aortic valve

    Presentation date: 2005.12

  • マイクロ波照射かつ拍動循環による処理は大動脈弁を強度維持したまま完全無細胞化しα1-3ガラクトース抗原も除去する

    Presentation date: 2005.11

  • Microwave treatment combined with pulsatile circulation can completely remove cells and α1-3 galactose antigen; vortex pump

    Presentation date: 2005.10

  • In vitro anti-thrombogenic screening of biomaterials under practical pulsatile circulation

    Presentation date: 2005.09

  • Microwave treatment combined with pulsatile circulation can completely remove cells and α1-3 galactose antigen

    Presentation date: 2005.09

  • 生理的拍動環境を創出可能な 血液適合性評価装置による医療用具及び医用材料のin vitro抗血栓性スクリーニン グ試験

    Presentation date: 2004.10

  • 生理的拍動環境を創出可能な血液適合性評価装置による医療用具及び医用材料のin vitro抗血栓性スクリーニング試験

    Presentation date: 2004.09

  • 急性心不全患者の心機能改善を目的とした超低価格拍動型の旋回渦流型補助人工心臓の開発戦略と性能試験

    Presentation date: 2004.09

  • 拍動循環下でのマイクロ波照射による組織脱細胞化及び生理的拍動環境での細胞播種技術に基づく動物実験用大動脈弁の開発

    Presentation date: 2004.09

  • Innovative decellularization and pre-endothelialization technologies to develop a tissue-engineered aortic valve

    Presentation date: 2004.09

  • A completely decellularized and pre-cellularized tissue engineered aortic valve using innovative bioreactor technologies,Advances in tissue engineering and biology of heart valves

    Presentation date: 2004.09

  • Development of a completely decellularized and precellularized functional porcine aortic valve

    Presentation date: 2004.07

  • A novel methodology for pre-screening anti-thrombogenicity of artificial organs under physiologically identical pulsatile environments

    Presentation date: 2004.07

  • In vitro accelerated calcification tester for biomaterials using real blood

    Presentation date: 2004.06

  • Innovative dynamic bioreactor technologies to realize a pre-endothelialized decellularized aortic heart valve

    Presentation date: 2004.06

  • 革新的動的バイオリアクター技術による再生・自己化促進型組織大動脈弁の開発

    Presentation date: 2004.05

  • A novel in vitro device to investigate a calcification mechanisum on cardiovascular implants

    Presentation date: 2004.01

  • 脱細胞化異種大動脈弁の開発:拍動循環下でのマイクロ波均一照射による完全脱細胞化および拍動循環での組織再内皮細胞化手法の検討

    Presentation date: 2004.01

  • 医用高分子材料の長期血液循環使用下で問題となるカルシウム沈着特性のin vitro 評価試験手法の新開発

    Presentation date: 2004.01

  • 新規の完全大気非接触型拍動流循環回路による人工臓器のin vitro 抗血栓性評価方法の確立に向けての挑戦

    Presentation date: 2004.01

  • 自分が使いたくなる再生型人工臓器の開発,及び人工臓器の開発のスピード化に寄与する協会領域の性能評価試験方法の確立に向けて

    Presentation date: 2004.01

  • Complete decellularization of xenogeneic aortic heart valves and in vitro re-endothelialization in a pulsatile circulation using novel bioreactors

    Presentation date: 2003.12

  • A novel in vitro methodology for blood compatibility tests for artificial organs in pulsatile flow and pressure environments

    Presentation date: 2003.08

  • A novel methodology to investigate a calcification potential of polymeric cardiovascular biomaterials under accelerated condition

    Presentation date: 2003.07

  • 拍動循環下でのマイクロ波照射によるブタ大動脈弁の完全脱細胞化手法の開発

    Presentation date: 2003.06

  • 大動脈弁置換用を目指したブタ組織弁の脱細胞化手法の検討及びin vitro拍動下での細胞播種用バイオリアクターの開発

    Presentation date: 2003.03

  • 人工臓器の血液適合性評価を目的とした生体内圧力・流量環境に合致した完全大気非接触in vitro評価回路の開発

    Presentation date: 2003.01

  • 長期機械的寿命の実現と同時にカルシウム沈着の長期抑制に成功した人工心臓用高分子製弁Jellyfish弁の開発

    Presentation date: 2003.01

  • 人工臓器のin vitro抗血栓性評価を目的とした完全大気非接触型拍動流試験回路の開発

    Presentation date: 2003.01

  • An inexpensive pulsatile blood pump:Fabrication strategies and in vitro reliable methodology to evaluate blood compatibility

    Presentation date: 2002.12

  • 高分子製人工弁Jellyfish弁の開発:カルシウム沈着の抑制と長期耐久性の実現

    Presentation date: 2002.10

  • 高分子製人工弁Jellyfish弁の開発: カルシウム沈着の抑制と長期耐久性の実現

    Presentation date: 2002.10

  • Development of a novel in-vitro closed circuit for anti-thrombogenic tests of cardiac prostheses under physiologic hemodynamic conditions

    Presentation date: 2002.06

  • カルシウム沈着抑制のための高分子製人工弁設計指標の提案

    Presentation date: 2002.03

  • Importance of dynamic-load conditions in the accelerated fatigue tests for polymer heart valves

    Presentation date: 2001.10

  • The improved jellyfish valve: Durability enhancement with Sufficient blood compatibility

    Presentation date: 2001.04

  • ダブルリム構造を有する改良型Jellyfish弁の動物実験による血液適応性評価

    Presentation date: 2000.08

  • Analysis of calification mechanism on jellyfish valve

    Presentation date: 2000.03

  • Extension of a duraaaability of jellyfish valve for long-term use in artificial hearts

    Presentation date: 2000.03

  • Analysis of calification mechanism on jellyfish valve

    Presentation date: 2000.03

  • 高分子製人工弁の加速耐久試験確立に向けての力学的検討

    Presentation date: 1999.09

  • Development of a durable of a durable polymer valve based on finite element analysis

    Presentation date: 1999.09

  • 耐久性向上を目指した高分子製人工心臓弁の設計改良と試作

    Presentation date: 1998.10

  • 医療用高分子材料の疲労が血液適合性に与える影響の基礎検討

    Presentation date: 1998.10

  • 医療高分子材料の疲労が血液適合性に与える影響の基礎検討

    Presentation date: 1998.10

  • In vitro performance of coronary stents

    Presentation date: 1998.08

  • 有限要素法を用いたひずみ解析によるJellyfish弁のカルシウム沈着発生位置の検討

    Presentation date: 1997.09

  • 有限要素数を用いたJellyfish弁の弁膜破断位置の検討

    Presentation date: 1997.04

  • コーティング材料の異なる拍動ポンプのIn vitro拍動流抗血栓性試験における凝固因子の比較評価

  • 無細胞化技術及び拍動バイオリアクター培養技術による心臓弁再生

  • Tissue-engineered robust vascular grafts utilizing the physiologically equivalent pulsatile bioreactor

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Specific Research

  • 大動脈弁の外側から取り付けて逆流を抑制する革新的低侵襲大動脈弁形成デバイス

    2022  

     View Summary

    本邦では超高齢化社会を迎え、弁機能不全等の慢性疾患は増加傾向にある。高齢者に対して人工心肺を必要とせずに低侵襲に治療できるデバイスの開発は患者のQOL向上・健康寿命延伸に貢献できる。本課題では血管を切り開かずに外側から大動脈弁に取り付けて弁機能を改善する革新的低侵襲治療デバイスの開発に着手した。まず治療対象となる大動脈弁閉鎖不全症モデルを研究開発した。新規開発に着手した低侵襲大動脈弁逆流抑制デバイスを大動脈弁閉鎖不全症モデルに取り付けて拍動循環シミュレータを用いて性能評価試験を実施した結果、大動脈弁逆流率が減少し、弁機能改善に有用であることが明らかになり、Proof of Conceptを取得できた。

  • 力学的完全異方性を踏まえた生体組織に生じるひずみの有限要素解析手法の開発

    2019   坪子 侑佑, 松橋 祐輝, 朱 暁冬

     View Summary

    &nbsp; 革新的医療機器や治療技術の開発においては、適用する生体組織の非線形かつ完全異方性で複合材料であるという特徴のモデル化が重要である。本課題では生体組織の三次元力学特性評価技術の確立を目的として、二軸引張試験による三次元力学特性評価機構を考案した。マイクロメータを用いた引張機構と三次元測定機からなる、組織の三次元形状を同時計測可能な二軸引張試験系を構築した。ウシ心膜を用いた引張試験から、応力集中が原因と考えられる組織局所での破断が観測された。今後、チャック部の改良、および、生体組織に均一に張力負荷を作用する機構の開発を進め、動的な変形に伴うひずみ・応力分布を高精度に計測可能な手法を提案する。

  • 脳血管血栓回収ステントの有効性向上の設計指針を取得する先進的生体代替試験法の開発

    2017   松橋祐輝

     View Summary

    心臓で血流停滞により形成された血栓により脳血管が閉塞すると、死亡や重度の障害を招く。そこで発症から8時間以内の急性期脳梗塞患者に対して、NiTi合金製の網目状構造を有する血栓回収デバイスで血栓を絡め、血管内で引き抜いてカテーテル内に収納して回収し、血流の再開通を図る治療法がある。本研究では、血栓回収デバイスの安全で有効な使用方法を開発することを目指し、血液を用いて血栓を作製し、その力学的特性を調整する方法、また、血栓の圧縮剛性等を計測する評価系を開発した。さらに、デバイス展開後にどのくらい待つと血栓が押し広げられて拡張径が一定値に漸近するのかを検証し、実臨床に貢献する知見を得ることができた。

  • 大動脈ステントグラフトを用いた治療目標達成度を評価する拍動流シミュレータ開発

    2015   植松美幸, 山崎健二

     View Summary

    弓部大動脈瘤の治療は、治療効果の高いステントグラフトの開発が望まれ、手技の難易度の高い挑戦的領域である。その理由は、心臓から拍動血流による負荷を受ける中でステントグラフトを展開し、ステントグラフトを曲がってねじれた血管壁に圧着させて瘤への血流を遮断しつつ、脳を還流する三分枝血管への血流を阻害しないことが要求されるためである。新規デバイスを患者に使う前に拍動流環境で操作性を体感でき、留置結果を定量評価できると、治療戦略立案に役立ち、治療手技の向上にも貢献し得る。本研究では、ステントグラフトの挿入から留置を弾性血管モデル内で拍動流存在下に体験し、留置結果を定量評価できるシミュレータを開発した。

  • 心臓の収縮・拡張に伴う冠動脈屈曲運動下でのステント破損予測解析

    2013  

     View Summary

    冠動脈ステント治療は,本邦で年間7%程度のステント破断が生じ,破断したステントでの再狭窄率は85%程度と非常に高い報告もある.一度留置すると取り出せないため,冠動脈に留置されるステントには高い破損耐久性が求められる.我々は心臓の収縮・拡張に伴う右冠動脈の屈曲変形に着目し,実臨床に即した冠動脈ステントの屈曲加速耐久試験装置を開発した.患者から得た右冠動脈屈曲角度の平均値である収縮期105deg,拡張期125degの角度を屈曲冠動脈モデルに作用する加速耐久試験装置を開発し,デザイン・材質の異なるステントに対し,屈曲加速耐久試験を実施してきた.本研究では,耐久試験結果でのステント破断の原因を明確化し,ステント破断予測を行うシステムを構築するため,有限要素法を用いた冠動脈屈曲変形下におけるステントの応力解析方法の構築を目的とした.解析はステント製造から実臨床で使用される一連の手順を踏まえ,以下の3ステップに分けた.(1)ステントをバルーンにかしめる圧縮解析(2)血管モデル内で円筒状にモデル化したバルーンを用いたステントの拡張・留置解析(3)ステントに屈曲負荷を作用させる屈曲負荷解析(3)の屈曲負荷解析は,血管モデルに収縮期105deg,拡張期125degを屈曲角度とする屈曲変形を作用させ,ステントへ間接的に屈曲負荷を作用させた.臨床で使用されているCoCr製のステントを対象とし,解析には非線形有限要素解析ソフト(ADINA8.9,ニュートンワークス)を使用した.解析より得たMisesの相当応力から応力振幅と平均応力を求め,疲労安全率を算出した.疲労安全率は屈曲中央のリンク部およびリンクが接合しているクラウン部で小さいことが明らかとなった.本解析対象ステントは耐久試験において,屈曲中央のリンク部でステント破断が生じており,疲労安全率の小さい部位と一致する傾向を確認できた.以上より,ステントをバルーンにかしめ,バルーンでステントを血管内に拡張し,屈曲変形を作用させる一連の有限要素解析方法を構築した.

 

Syllabus

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Committee Memberships

  • 2022.04
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    Now

    日本医療機器テクノロジー協会ISO/TC194, ISO/TC150 (SC2, SC6)  国内委員会 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  庶務会則委員会 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  財務委員会 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  学会活性化(循環系)WG 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  学会活性化(広領域)WG 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  選奨委員会 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  論文賞選出(循環系)委員会 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  選出評議員候補者選出委員会 委員

  • 2022.02
    -
    Now

    日本人工臓器学会  研究推進委員会 副委員長

  • 2022.02
    -
    Now

    日本人工臓器学会  医療産業促進委員会 委員長

  • 2022.02
    -
    Now

    日本人工臓器学会  大会賞萌芽研究ポスター賞WG 委員長

  • 2022.02
    -
    Now

    日本人工臓器学会  レギュラトリーサイエンス委員会 委員長

  • 2021.05
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    Now

    日本バイオレオロジー学会  企画小委員会ティッシュエンジニアリング・人工臓器副査

  • 2021.05
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    Now

    日本バイオレオロジー学会  バイオレオロジー・リサーチ・フォーラム運営委員会委員長

  • 2021.05
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    Now

    日本バイオレオロジー学会  企画委員会委員

  • 2021.05
    -
    Now

    日本バイオレオロジー学会  理事

  • 2021.05
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    Now

    日本バイオレオロジー学会  企画理事

  • 2021.04
    -
    Now

    日本機械学会  医工学テクノロジー推進会議運営委員会委員

  • 2020.04
    -
    Now

    公益財団法人吉田育英会  選考委員

  • 2020.04
    -
    Now

    独立行政法人医薬品医療機器総合機構  専門委員

  • 2020
    -
    Now

    Artificial Organ  Editorial Board

  • 2019
    -
    Now

    日本循環器学会  重症心不全に対する植込み型補助人工心臓治療ガイドライン作成班協力員

  • 2018.05
    -
    Now

    ライフサポート学会  理事

  • 2017.06
    -
    Now

    日本機械学会バイオエンジニアリング部門  代議員

  • 2017.01
    -
    Now

    厚生労働省 薬事・食品衛生審議会  医療機器・再生医療等製品安全対策部会員

  • 2016.10
    -
    Now

    日本生体医工学会  新技術開発賞選定委員会幹事

  • 2016.09
    -
    Now

    日本生体医工学会  新技術開発賞選定委員

  • 2016.02
    -
    Now

    日本人工臓器学会レギュラトリーサイエンス委員会  委員

  • 2014.11
    -
    Now

    日本再生医療学会  代議員

  • 2013
    -
    Now

    日本バイオレオロジー学会  理事

  • 2013
    -
    Now

    日本医療機器テクノロジー協会 ISO10993-4 TC194 WG-9  国内委員会 副主査(Effects of blood)

  • 2011
    -
    Now

    日本循環制御学会  評議員

  • 2011
    -
    Now

    日本バイオマテリアル学会  評議員

  • 2010
    -
    Now

    ライフサポート学会フロンティア講演会  管理委員会委員

  • 2004
    -
    Now

    日本人工臓器学会  評議員

  •  
    -
    Now

    IEEE Engineering in Medicine and Biology Society  Conference Editorial Board

  • 2020.04
    -
    2022.03

    国立研究開発法人国立国際医療研究センター  臨床研究審査委員会 技術専門員

  • 2019.11
    -
    2021.10

    独立行政法人医薬品医療機器総合機構  コンピューターシミュレーションを活用した医療機器ソフトウェアの審査の考え方に関する専門部会 委員

  • 2019.04
    -
    2020.03

    日本機械学会  バイオエンジニアリング部門運営委員

  • 2018.09
    -
    2020.03

    独立行政法人医薬品医療機器総合機構  専門委員

  • 2016.04
    -
    2020.03

    (4) 日本医療機器テクノロジー協会 TC150 SC2 WG-3 (Vascular stent), SC2 WG-7 (Bioabsorbable stent)  国内委員会 委員

  • 2018.03
    -
    2019.06

    日本生体医工学会  第58回大会 プログラム委員

  • 2018.09
    -
    2019.03

    日本機械学会  学会賞委員会 委員

  • 2014.04
    -
    2019.03

    日本機械学会バイオエンジニアリング部門「Journal of Biomechanical Science and Engineering」  Associate Editor

  • 2018
    -
    2019

    日本生体医工学会  臨床研究法WG 委員

  • 2013.05
    -
    2018.05

    ライフサポート学会  評議員

  • 2016.08
    -
    2018.03

    厚生労働省 平成28年度・29年度次世代医療機器評価指標作成事業  「血流シミュレーションソフトウェア分野」審査ワーキンググループ委員

  • 2016.09
    -
    2017.03

    日本機械学会学会賞委員会  委員

  • 2015.10
    -
    2017.03

    厚生労働省 平成27年度・28年度次世代医療機器評価指標作成事業  「生体由来材料分野」審査ワーキンググループ委員

  • 2015.10
    -
    2017.03

    厚生労働省  ワーキンググループ委員

  • 2017
     
     

    JST CRDS ライフサイエンス・臨床医学分野  研究開発の俯瞰報告書、医療技術評価(医療機器) 作成協力者

  • 2015.05
    -
    2017

    日本生体医工学会  代議員

  • 2014.08
    -
    2016.03

    独立行政法人医薬品医療機器総合機構  科学専門部会委員

  • 2014.08
    -
    2016.03

    厚生労働省 平成27年度・28年度次世代医療機器評価指標作成事業  「生体吸収性ステント審査ワーキンググループ」委員

  • 2012
    -
    2016

    科学研究費委員会  専門委員

  • 2013.05
    -
    2015.03

    日本機械学会  バイオエンジニアリング部門企画委員会委員

  • 2010.04
    -
    2015.03

    日本機械学会バイオエンジニアリング部門  運営委員

  • 2014
     
     

    日本機械学会  年次大会委員

  • 2010
    -
    2013.04

    日本バイオレオロジー学会  評議員

  • 2012
    -
    2013

    日本循環器学会  重症心不全に対する植込み型補助人工心臓治療ガイドライン作成班協力員

  • 2012
    -
    2013

    補助人工心臓有害事象検討会  委員

  • 2007
    -
    2012.04

    日本人工臓器学会  英文誌「Journal of Artificial Organs」Editorial Board,Managing Editor.和文誌「人工臓器」 編集委員

  • 2007
    -
    2012.04

    日本人工臓器学会  編集委員

  • 2012
     
     

    ライフサポート学会フロンティア講演会  大会長

  • 2011
    -
    2012

    日本機械学会  出版センター委員

  • 2009
    -
    2012

    日本機械学会バイオエンジニアリング部門  関東支部代議員

  • 2010
    -
    2011

    内閣官房医療イノベーション推進室  医療機器ワーキングチーム委員

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