植入式心脏起搏器的聚焦超声无线供能基础研究

The existing implantable cardiac pacemakers which use disposable batteries have a problem of re-operation to replace the pacemaker or battery when power is run out. In 2007, the EBR system Inc. in US proposed the first human wireless pacemaker with ultrasound energy delivery in non-invasive way to achieve a continuous power supply. Ultrasound wireless power transmission can overcome the poor penetrability, large volume, electromagnetic radiation and electromagnetic interference in electromagnetic coupling way. However, in the above study, the propagation of ultrasound in certain parts of the body was not yet clear. The fundamental research on the mechanism of efficient acoustic-electric conversion for ultrasound and the optimal operating rule of the system which caused the energy reception efficiency of only 0.063% were still blank. And another issue was substantial beat-to-beat variation observed in the receiver electrode output. To solve the above problems, combining with our preliminary research on this subject, we proposed a way of wireless energy transmission for cardiac pacemakers using the low frequency-pulsed-focused ultrasound. Phase-matching theory, energy trapping theory in vibration and electrode optimization theory for receiving transducer were employed to analyze the model of the implantable cardiac pacemaker. Then, the mechanical energy in focused ultrasound was converted into electricity efficiently. Finally the electricity generated in the receiving transducer was theoretically calculated. This study will provide theoretical support for implantable cardiac pacemakers with an efficient and stable wireless energy transmission using ultrasound.

现有植入式心脏起搏器都采用一次性电池供电，存在再次手术更换起搏器或电池的难题，2007年美国EBR系统公司制作出世界首个超声波供能无线心脏起搏器，用超声波以无线无创的方式实现了对起搏器的持续供电，并克服了电磁耦合无线供能方式存在穿透性不强、体积偏大、电磁辐射及电磁干扰等缺点。但是，以上研究对超声波在人体某些特定部位的传播过程还未明确，对超声波高效声电转化机制和系统最优工作规律的基础研究尚属空白，造成仅有0.063%的能量接收效率，且各起搏次之间差异性较大。为解决以上难题，本课题结合申请者前期在超声波无线供能理论的研究成果，拟采用低频脉冲聚焦超声实现起搏器的无线供能，将接收换能器的相位匹配理论、振动能陷理论及电极优化理论引入到起搏器模型分析中，高效提取聚焦超声波的机械能并将其转化成电能，并对接收换能器上产生的电能进行理论计算，为实现植入式心脏起搏器的超声波高效、稳定无线供能提供理论支撑。

针对现有植入式心脏起搏器都采用一次性电池供电，存在再次手术更换起搏器或电池的难题。为解决这个问题，本项目提出了用超声波无线供能驱动植入式器械的方法。主要进展包括，建立了1-3型压电复合材料俘能器Thickness stretch（厚度伸缩）理论模型，与阻抗分析仪实测结果吻合；在理论和实验上分析了压电俘能器接收超声纵波能量的工作规律及负载最优匹配规律，结果显示当负载阻抗等于俘能器阻抗时效率最高，且在正谐振点和反谐振点上输出效率最高；搭建了一套水中超声波无线传输的实验装置，结果显示超声波传输约5cm后，将与1-3型压电复合材料俘能器连接的LED灯泡点亮，功率为毫瓦级；建立了聚焦超声无线供能的植入式心脏起搏器的原理模型，为下一步临床实验提供了理论参考。