Miniaturization and Performance Enhancement of the Magnetically Levitated Centrifugal Pump as an Implantable Ventricular Assist Device

本研究的目的是提高磁悬浮叶轮离心泵作为左心室辅助装置的性能和生物相容性，最终开发一种植入式心脏辅助系统。本研究取得的主要成果如下：1.悬浮控制电路的小型化和稳定性增强设计了控制转子(叶轮)径向悬浮和旋转的电子电路，并在紧凑型离心泵中实现。通过数值模拟，得到了定子内外径和匝数的最佳值。在分析结果的基础上设计了试验台泵，实现了作为左心室辅助装置的足够的流体动力性能。采用零功率控制方法，并将其应用于悬浮系统中。零功率系统设置t…将目标控制在径向流体作用力最小的位置，从而节省了悬浮系统所需的电能。建立了电磁元件的数值模型，得到了永磁体厚度、定子直径和线圈匝数的优化设计方案。最后将定子直径设置为55 mm，成功地将总功率降至11瓦。在定子和转子之间的间隙处，血液通道的最小间隙为0.5 mm。并进行溶血试验，以确定其对红细胞的机械损伤在临床可耐受范围内。结果表明，该泵对血液的机械性损伤与市售美敦力BP-80泵(美敦力BP-80)相当，流量为5.0mHg.min，压头为100mmHg.并对泵的流量估算方法进行了研究。由于零功率控制的结果，叶轮位置在每种流动状态下都会移动到平衡位置。我们发现叶轮偏离几何中心的位移与流量成正比。这种基本原理可以发展成不需要任何流量计的流量测量系统。较少

The purpose of the present study is enhancement of the performances and the biocompatibility of the centrifugal pump with magnetically levitated impeller as a left ventricular assist device, with the final goal of development of an implantable ventricular assist system.The primary results obtained through this study are as follows;1. Miniaturization and Stability Enhancement of the Levitation Controlling CircuitThe electronic circuits which control both radial levitation and rotation of the rotor (impeller) were designed to be implemented in the compact centrifugal pump. Numerical Simulations were carried out to obtain the optimized values of the inner/outer diameters of the stator, and the number of turns. The test rig pump was designed based on the analyses results, and the sufficient hydrodynamic performances were realized as a left ventricular assist device.2. The zero-power control method was employed and implemented into the present levitation system. The zero-power system sets t … More he control target onto the position where the radial fluid forces are minimized, and consequently save the electric power required to the levitation system. We built the numerical modeling of the electromagnetic components and then obtained the optimized thickness of the permanent magnets, diameter of the stator, and the number of turns of electric coils. Finally the diameter of the stator was set to 55 mm and we have succeeded in reducing the total electric power to 11 watts.3. The smallest clearance of the blood passage was 0.5 mm at the gap between the stator and the rotor. The hemolysis tesing was carried out to confirm the mechanical damage exerted to the red blood cells are within tolerable range toward clinical application. The results showed that the mechanical blood damage caused by the pump are compatible to that by the commercially available pump (Medtronic BP-80) at the flow rate of 5.0 L/min against the pressure head of 100 mmHg.4. The method of estimating the flow rate of the pump are also investigated. As the result of the zero-power control, the impeller positions shift to the balanced position on each flow condition. We have found the displacement of the impeller from the geometrical center are proportional to the flow rate. This basic founding can be developed into the flow rate measurement system which does not require any flow meter in the system. Less