Takashi Yamane

Kobe University, Kōbe, Hyōgo, Japan

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Publications (143)139.2 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study is to evaluate a spiral groove geometry for a thrust bearing to improve the hemolysis level in a hydrodynamically levitated centrifugal blood pump. We compared three geometric models: (i) the groove width is the same as the ridge width at any given polar coordinate (conventional model); (ii) the groove width contracts inward from 9.7 to 0.5 mm (contraction model); and (iii) the groove width expands inward from 0.5 to 4.2 mm (expansion model). To evaluate the hemolysis level, an impeller levitation performance test and in vitro hemolysis test were conducted using a mock circulation loop. In these tests, the driving conditions were set at a pressure head of 200 mm Hg and a flow rate of 4.0 L/min. As a result of the impeller levitation performance test, the bottom bearing gaps of the contraction and conventional models were 88 and 25 μm, respectively. The impeller of the expansion model touched the bottom housing. In the hemolysis test, the relative normalized index of hemolysis (NIH) ratios of the contraction model in comparison with BPX-80 and HPM-15 were 0.6 and 0.9, respectively. In contrast, the relative NIH ratios of the conventional model in comparison with BPX-80 and HPM-15 were 9.6 and 13.7, respectively. We confirmed that the contraction model achieved a large bearing gap and improved the hemolysis level in a hydrodynamically levitated centrifugal blood pump. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
    No preview · Article · Jul 2015 · Artificial Organs
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    ABSTRACT: The relative permittivity ε′ and the dielectric loss ε″ for various hematocrit values H for static bovine blood condition have been measured using the dielectric relaxation method to detect thrombosis in real time. The suitable measurement frequency f m ranged within 60 kHz to 1 MHz, and the relaxation frequency of red blood cells (RBCs) f rc was observed to be 2 MHz. In the f m, the temporal change of normalized ε′ exhibited a minimum (called as bottom point). The bottom point was observed to be exponentially shortened as H increased. This characteristic of the ε′* minimum is discussed from three viewpoints: during fibrin formation, direct thrombus formation, and rouleaux formation processes. ε′* during the fibrin formation process decreased over time, irrespective of f. However, ε′* in f m during the direct thrombus formation process and during the aggregation formation process increased immediately and rapidly over time. Therefore, the ε′* bottom point in f m might be the indication of micrometer-scale thrombus formation by RBC aggregation due to fibrin formation.
    No preview · Article · Jun 2015 · Journal of Artificial Organs
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    ABSTRACT: Primary gastric choriocarcinoma (PGC) is highly malignant and metastatic; hence, the median survival period remains at less than five months in recurrent or unresectable cases where the patient has been treated with a chemotherapy regimen for advanced gastric carcinoma. Furthermore, the complication of metastasis worsens the clinical state of patients. For these reasons, there is no concurrence regarding the optimal management strategy for metastasis of PGC. A 79-year-old man underwent a comprehensive medical examination during which he was found to have PGC with liver, lung and lymph node metastases. Cystoscopy and pelvic computed tomography for survey of further metastasis demonstrated a tumor in the right side wall of the bladder. Histological examination following transurethral resection of the bladder tumor revealed metastasis of PGC. After this diagnosis, the patient was maintained on chemotherapy using capecitabine, cisplatin, TS-1, paclitaxel and Trastuzumab. The patient survived for a period of 9 months following the diagnosis of PGC. No recurrence of the bladder tumor was observed during the clinical course. © 2015, Nishinihon Section of Japan Urological Association. All rights reserved.
    No preview · Article · May 2015 · Nishinihon Journal of Urology
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    ABSTRACT: A 57-year old man was given a diagnosis of left renal pelvic carcinoma (cT4N1M0). The tumor was considered to be unresectable, and it was pathologically proven to be urothelial carcinoma, Grade 3, by percutaneous needle biopsy. The patient was treated with external-beam radiotherapy and MVAC chemotherapy (Methotrexate, Vinblastine, Adriamycin and Cisplatin). The size of the renal pelvic tumor was markedly decreased and paraaorta lymph node metastasis was markedly reduced following treatment. As of now, more than seven years after the commencement of treatment, the left renal pelvic carcinoma and paraaorta lymph node metastasis have both been controlled by UFT administration. © 2015, Nishinihon Section of Japan Urological Association. All rights reserved.
    No preview · Article · May 2015 · Nishinihon Journal of Urology
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    ABSTRACT: Various extracorporeal circulation devices require a real time thrombus detection system. This paper presents a study toward the establishment of real-time thrombus detection by measuring the electrical properties of blood. We conducted experiments on static bovine blood samples and determined the change in relative permittivity of the samples by changing the size and red blood cell (RBC) concentration of the thrombus in each sample. Results show that the relative permittivity increases linearly with increases in the number of RBCs that form the thrombus. Similarly, permittivity also increases linearly with increases in the volume of the blood that forms the thrombus. These results are consistent with the numerical simulations. However, we found the linear relationship to be dependent on the AC frequency of the applied voltage. We compare and explain this dependency on the basis of earlier studies.
    Preview · Article · Jan 2015 · Journal of Biorheology
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    ABSTRACT: We have developed a hydrodynamically levitated centrifugal pump as a bridge-to-decision device. The purpose of the present study is to determine the optimal bearing gap of a multiarc radial bearing in the developed blood pump for the reduction of hemolysis. We prepared eight pump models having bearing gaps of 20, 30, 40, 80, 90, 100, 180, and 250 μm. The driving conditions were set to a pressure head of 200 mm Hg and a flow rate of 4 L/min. First, the orbital radius of the impeller was measured for the evaluation of the impeller stability. Second, the hemolytic property was evaluated in an in vitro hemolysis test. As a result, the orbital radius was not greater than 15 μm when the bearing gap was between 20 and 100 μm. The relative normalized index of hemolysis (NIH) ratios in comparison with BPX-80 were 37.67 (gap: 20 μm), 0.95 (gap: 30 μm), 0.96 (gap: 40 μm), 0.82 (gap: 80 μm), 0.77 (gap: 90 μm), 0.92 (gap: 100 μm), 2.76 (gap: 180 μm), and 2.78 (gap: 250 μm). The hemolysis tended to increase at bearing gaps of greater than 100 μm due to impeller instability. When the bearing gap decreased from 30 to 20 μm, the relative NIH ratios increased significantly from 0.95 to 37.67 times (P < 0.01) due to high shear stress. We confirmed that the optimal bearing gap was determined between 30 and 100 μm in the developed blood pump for the reduction of hemolysis.
    No preview · Article · Sep 2014 · Artificial Organs
  • A. Sapkota · T. Fuse · O. Maruyama · R. Kosaka · T. Yamane · M. Takei
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    ABSTRACT: The ventricular assistance devices (VAD) have been very useful to the patients with chronic heart failures. But, regular consumption of anticoagulants to suppress the thrombosis results into many bleeding related complications. Such complications are also observed in the patients getting hemodialysis and patients undergoing heart surgery using heart-lung machine. Currently, the anticoagulation management is based on offline tests. But, the real-time non-invasive blood monitoring system is highly desirable to optimize the anticoagulation therapy. As a basic study in that direction, we employed electrical impedance spectroscopy (EIS) method to study the electrical chacteristics of bovine blood under thrombogenic condition. The resistance and reactance were measured in the frequency range of 1 kHZ to 5MHz. The measured values were then analyzed using equivalent circuit fitting. It was observed that the capacitance of the blood can be used to quantitatively measure the degree of aggregation of red blood cells in the blood undergoing thrombosis. © 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.
    No preview · Article · Aug 2014 · Transactions of Japanese Society for Medical and Biological Engineering
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    ABSTRACT: Dielectric relaxation method has been proposed for the possibility of real-time detection of thrombosis by exploiting the electrical properties of the blood. In-vitro experiments were conducted with bovine blood to measure relative permittivity and dielectric loss in the case of various hematocrit values under static blood condition. As a result, the relaxation frequency of the electrode and red blood cells were observed at 20 kHz and 2 MHz respectively. The characteristics frequency showing the permittivity of the red blood cells membrane was in the range of 60 kHz to 1 MHz. The time variations of resistivity and relative permittivity were observed at this frequency range of characteristics frequency of red blood cell membrane. Resistivity and relative permittivity measured at this frequency range increased in the case of the increase in the hematocrit values. Additionally, a peak was observed in the temporal change in relative permittivity only in the case of that frequency range. Moreover, from the results of visual check of thrombosis, this peak indicated the start of the micro-thrombus formation. This phenomenon was specific to the thrombosis, and was observed only in the presence of red blood cells. The experiments showed the possibility of the real time detection of thrombosis for implantable ventricular assistance devices, heart-lung machines and artificial kidney.
    No preview · Article · Jan 2014
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    ABSTRACT: Currently, patients who undergo extracorporeal blood circulation require regular antithrombotic drugs which cause side-effects. In order to minimize the side-effect, the thrombus needs to be detected in its early stage. In this study, we have investigated the effects of calcium ion on thrombus formation by measuring time variation of the relative resistivity. The visualization of thrombus formation after adding an aqueous solution of calcium chloride (CaCl2) of different concentrations to the blood has been accomplished using electrical resistivity tomography technique. The thrombosis started earlier with relatively large thrombus at the end for increased concentration of calcium ions. © 2014 International Society for Industrial Process Tomography.
    No preview · Article · Jan 2014
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    ABSTRACT: The purpose of the present study is to establish an optimal design of the multi-arc hydrodynamic bearing in a centrifugal blood pump for the improvement of bearing stiffness and hemolysis level. The multi-arc bearing was designed to fulfill the required specifications: (i) ensuring the uniform bearing stiffness for various bearing angles; (ii) ensuring a higher bearing stiffness than the centrifugal force to prevent impeller whirl; and (iii) adjusting the bearing clearance as much as possible to reduce hemolysis. First, a numerical analysis was performed to optimize three design parameters of the multi-arc bearing: number of arcs N, bearing clearance C, and groove depth H. To validate the accuracy of the numerical analysis, the impeller trajectories for six pump models were measured. Finally, an in vitro hemolysis test was conducted to evaluate the hemolytic property of the multi-arc bearing. As a result of the numerical analysis, the optimal parameter combination was determined as follows: N = 4, C = 100 μm, and H ≥ 100 μm. In the measurements of the impeller trajectory, the optimal parameter combination was found to be as follows: N = 4, C = 90 μm, and H = 100 μm. This result demonstrated the high reliability of the numerical analysis. In the hemolysis test, the parameter combination that achieved the smallest hemolysis was obtained as follows: N = 4, C = 90 μm, and H = 100 μm. In conclusion, the multi-arc bearing could be optimized for the improvement of bearing stiffness and hemolysis level.
    No preview · Article · Aug 2013 · Artificial Organs
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    ABSTRACT: A hydrodynamically levitated centrifugal blood pump with a semi-open impeller has been developed for mechanical circulatory assistance. However, a narrow bearing gap has the potential to cause hemolysis. The purpose of the present study is to optimize the geometric configuration of the hydrodynamic step bearing in order to reduce hemolysis by expansion of the bearing gap. First, a numerical analysis of the step bearing, based on lubrication theory, was performed to determine the optimal design. Second, in order to assess the accuracy of the numerical analysis, the hydrodynamic forces calculated in the numerical analysis were compared with those obtained in an actual measurement test using impellers having step lengths of 0%, 33%, and 67% of the vane length. Finally, a bearing gap measurement test and a hemolysis test were performed. As a result, the numerical analysis revealed that the hydrodynamic force was the largest when the step length was approximately 70%. The hydrodynamic force calculated in the numerical analysis was approximately equivalent to that obtained in the measurement test. In the measurement test and the hemolysis test, the blood pump having a step length of 67% achieved the maximum bearing gap and reduced hemolysis, as compared with the pumps having step lengths of 0% and 33%. It was confirmed that the numerical analysis of the step bearing was effective, and the developed blood pump having a step length of approximately 70% was found to be a suitable configuration for the reduction of hemolysis.
    No preview · Article · Jul 2013 · Artificial Organs
  • T Yamane · K Kitamura
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    ABSTRACT: We are developing an axial-flow pump with a cylindrical-impeller without airfoils. In the mock experiments of HA02 model a pressure of 13.3 kPa was obtained at a rotational speed of 12500 rpm and flow of 5L/min. The obtained pressure with HA02 was almost double than an airfoil-type impeller. The 2D analysis of hydrodynamic bearings for the pump revealed that a section with 3 or more arcs is stable with respect to angular position, and a minimum bearing gap of 100µm can be attained at a design bearing gap of 150 µm and at a groove depth of 100µm.
    No preview · Article · Jul 2013 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
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    ABSTRACT: The effect of a cutout on the pump pressure-flow characteristics and the impeller stability was quantified using computational fluid dynamics analysis in order to provide good hemocompatibility of the monopivot extracorporeal circulation pump. As a result, the following findings were clarified. The pump pressure is lower in the cutout model than in the no-cutout model. The impeller stability with respect to the buoyancy of the impeller is better in the cutout model than in the no-cutout model. The impeller stability with respect to the impeller tilt is better in the cutout model than in the no-cutout model. Therefore, the cutout model, in which the geometry corresponds to the commercialized pump, was likely to be better than the no-cutout model because the stability that has the possibility to decrease the gap instantaneously to increase hemolysis despite the impeller rotational speed slightly.
    No preview · Article · Jul 2013 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
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    ABSTRACT: In order to monitor the condition of a patient using a left ventricular assist system (LVAS), blood flow should be measured. However, the reliable determination of blood-flow rate has not been established. The purpose of the present study is to develop a noninvasive blood-flow meter using a curved cannula with zero compensation for an axial flow blood pump. The flow meter uses the centrifugal force generated by the flow rate in the curved cannula. Two strain gauges served as sensors. The first gauges were attached to the curved area to measure static pressure and centrifugal force, and the second gauges were attached to straight area to measure static pressure. The flow rate was determined by the differences in output from the two gauges. The zero compensation was constructed based on the consideration that the flow rate could be estimated during the initial driving condition and the ventricular suction condition without using the flow meter. A mock circulation loop was constructed in order to evaluate the measurement performance of the developed flow meter with zero compensation. As a result, the zero compensation worked effectively for the initial calibration and the zero-drift of the measured flow rate. We confirmed that the developed flow meter using a curved cannula with zero compensation was able to accurately measure the flow rate continuously and noninvasively.
    No preview · Article · Jul 2013 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
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    ABSTRACT: Monitoring of thrombogenic process is very important in ventricular assistance devices (VADs) used as temporary or permanent measures in patients with advanced heart failure. Currently, there is a lack of a system which can perform a real-time monitoring of thrombogenic activity. Electrical signals vary according to the change in concentration of coagulation factors as well as the distribution of blood cells, and thus have potential to detect the thrombogenic process in an early stage. In the present work, we have made an assessment of an instrumentation system exploiting the electrical properties of blood. The experiments were conducted using bovine blood. Electrical resistance tomography with eight-electrode sensor was used to monitor the spatio-temporal change in electrical resistivity of blood in thrombogenic and non-thrombogenic condition. Under non-thrombogenic condition, the resistivity was uniform across the cross-section and average resistivity monotonically decreased with time before remaining almost flat. In contrary, under thrombogenic condition, there was non-uniform distribution across the cross-section, and average resistivity fluctuated with time.
    No preview · Article · Jul 2013 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
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    ABSTRACT: We have developed a hydrodynamically levitated centrifugal blood pump for extracorporeal circulatory support as a bridge to decision pump. The impeller is levitated using hydrodynamic bearings without any complicated control circuit or displacement sensor. However, the effect of the outer circumferential velocity and the bearing area on the hemolytic property has not been clarified, even if the bearing gap is same size. The purpose of this study is to experimentally evaluate the effect of the outer circumferential velocity and the bearing area in the bearing gaps on the hemolytic property in a hydrodynamically levitated centrifugal blood pump. We prepared three models for testing. These models have the same bearing gap size by adjusting the impeller levitation position. However, the outer circumferential velocity of the impeller and the bearing area in the minimum bearing gaps are different. The outer circumferential velocity of the impeller and the bearing area were assumed to be related to the maximum shear rate and the exposure time. For the evaluation, we conducted an impeller levitation performance test and an in vitro hemolysis test. As a result, the normalized index of hemolysis (NIH) was reduced from 0.084 g/100L to 0.040 g/100L corresponding to a reduction in the outer circumferential velocity and a reduction in the bearing area, even if the minimum bearing gaps were same size. We confirmed that, even if the bearing gap was same size under the stably levitated condition, the outer circumferential velocity and the bearing area should be decreased in order to improve the hemolytic property.
    No preview · Article · Jul 2013 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
  • H. Hayami · H. Enokida · T. Yamane · M. Nakagawa · M. Takei

    No preview · Article · Jun 2013
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    ABSTRACT: We have developed a hydrodynamically levitated centrifugal blood pump with a semi-open impeller for long-term circulatory assist. The pump uses hydrodynamic bearings to enhance durability and reliability without additional displacement-sensors or control circuits. However, a narrow bearing gap of the pump has a potential for hemolysis. The purpose of this study is to develop the hydrodynamically levitated centrifugal blood pump with a semi-open impeller, and to evaluate the effect of a bearing gap on hemolytic property. The impeller levitates using a spiral-groove type thrust bearing, and a herringbone-groove type radial bearing. The pump design was improved by adopting a step type thrust bearing and optimizing the pull-up magnetic force. The pump performance was evaluated by a levitation performance test, a hemolysis test and an animal experiment. In these tests, the bearing gap increased from 1 to 63 μm. In addition, the normalized index of hemolysis (NIH) improved from 0.415 to 0.005 g/100 l, corresponding to the expansion of the bearing gap. In the animal experiment for 24 h, the plasma-free hemoglobin remained within normal ranges (<4.0 mg/dl). We confirmed that the hemolytic property of the pump was improved to the acceptable level by expanding the bearing gap greater than 60 μm.
    No preview · Article · Feb 2013 · Bio-medical materials and engineering
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    ABSTRACT: In this paper, we present an application of electrical resistance tomography to analyze the formation of thrombosis in blood. Experiments were conducted using bovine blood under thrombogenic conditions. The concentration of red blood cells in the blood was varied to see the cell concentration dependent detection of thrombogenic process. The initial changes in thrombogenic conditions, which are due to change in plasma proteins, were noticed in cell-free condition. But, it was difficult to notice the changes caused by plasma proteinsin the presence of natural level of cell concentration. © 2014 International Society for Industrial Process Tomography.
    No preview · Article · Jan 2013

  • No preview · Article · Jan 2013

Publication Stats

772 Citations
139.20 Total Impact Points

Institutions

  • 2012-2015
    • Kobe University
      • Department of Mechanical Engineering
      Kōbe, Hyōgo, Japan
  • 2002-2015
    • National Institute of Advanced Industrial Science and Technology
      • National Institute of Advanced Industrial Science and Technology (AIST)
      Tsukuba, Ibaraki, Japan
  • 1999-2008
    • University of Tsukuba
      • Institute of Clinical Medicine
      Tsukuba, Ibaraki, Japan
  • 2000
    • Ibaraki University
      • Department of Mechanical Engineering
      Mito-shi, Ibaraki, Japan
  • 1999-2000
    • Mohawk Innovative Technology, Inc.
      Albany, New York, United States