【作者】 唐治德；

【导师】 孙才新；

【作者基本信息】 重庆大学 ， 电气工程， 2007， 博士

【摘要】 各类植入电子器件的公共技术问题之一是如何有效地向植入电子器件提供足够的电能,维持其长期、稳定、可靠地运行,实现其预期的功能。尽管植入电子器件存在多种可能的供电方案,但目前只有电池供电和磁感应供电技术得到广泛的临床应用。对电池供电的植入电子器件,由于电池容量受限,导致植入电子器件的使用寿命较短,例如心脏起搏器的实际寿命是2-5年。当然,磁感应耦合技术可将丰富的体外电能传递到体内植入电子器件,但由于生物体中存在着大量的离子型体液,其传导作用使磁感应耦合效率低;同时,为了向植入电子器件提供足够的能量,磁感应耦合的发射线圈必须发射较强的射频功率,它又将对附近的医学设备等形成较强的射频干扰。为了克服磁感应技术的缺点和延长植入电子器件的使用寿命,本文提出利用生物组织的体导电特性将体外电能跨皮肤地传递到植入电子器件的可充电电池来维持植入电子器件长期、稳定、可靠地运行。本文重点研究了体导电能量传递的原理,即采用紧贴皮肤的电极组(称为电极皮肤单元),利用生物组织的离子型传导电流将激励到体外电极组的电能耦合到体内电极组,并传递到植入电池和电子器件。考虑到电极的极化效应和离子型传导电流的特点,体导电能量传递系统的电流应为交流电流,从而形成了体导电能量传递的技术方案。为了有效地分析体导电能量传递系统的特性,建立了具有明确物理意义的电极皮肤单元的X型等效电路模型,导出了X型等效电路参数与电极开路阻抗关系的计算公式;以电极皮肤单元的X型等效电路模型为基础,提出了分析体导电能量传递系统特性的电路分析方法。与数值计算电极皮肤单元的泊松方程或拉普拉斯方程比较,电路分析方法具有计算简单、概念明确的特点,能分析体导电能量传递系统的整体特性。用电路分析方法系统地分析了体导电能量传递电路的特性:交流电流传递效率、植入电池的充电条件、充电电流传递效率、能量传递效率。通过电路分析,发现了决定体导电能量传递系统特性的主要参数:输入回路阻抗比(ILIR)、输出回路阻抗比(OLIR)和电压比(V1/V2),这些参数确定了体导电能量传递的效率。由此,提出了提高体导电能量传递效率的方法:阻抗法和电压法。通过电路分析,还发现了体导电能量传递系统的另一些重要特性:植入电池的充电条件和充电电流传递效率极限。根据植入电池的充电条件和实验验证,作用在体外电极组的最佳信号波形是交变方波。根据体导电能量传递技术方案和电路分析结果,设计和制作了体导电能量传递原型电路。实验结果是:在工作频率为5 kHz时,通过新鲜的猪皮传递到电池的充电电流是2.8 mA,相应的充电电流传递效率达到27%,能量传递效率为11%。理论和实验均证明:生物组织的体导电特性可以有效地将体外电能跨皮肤地传递到体内的植入电子器件。更多还原

【Abstract】 The power supply is a common concern for implantable devices. There are several possible approaches to power implants, however, only battery and magnetic inductive coupling are practical. The service life of an implantable device powered by a battery is short because of the limited battery capacity. For example, the real service life for a cardiac pacemaker is 2-5 years. On the other hand external rich energy can be transformed into implantable devices by magnetic inductive coupling. But its conversion efficiency in power delivery is generally poor due to the energy loss in conductive biological tissue . In order to maintain a sufficient amount of power transfer, a large RF power must be transmitted. This causes RF interference to nearby medical instruments.In order to avoid the major drawback of magnetic inductive coupling method and expand the service life of implantable devices this paper presents the energy delivery process based on volume conduction across skin and connective tissue. An x-type equivalent circuit model for the energy delivery process has been constructed and a circuit analysis method based on the model has been proposed. The circuit analysis method is useful and can be applied for whole volume conduction energy delivery system. Theoretical analyses and experiments had been conducted to evaluate the characteristics of energy delivery based on volume conduction, such as, AC current transmission efficiency, implantable battery recharging condition, recharging current transmission efficiency, energy transmission efficiency. According to circuit analysis three important parameters were defined to evaluate performance of power delivery. These parameters are Input Loop Impedance Ratio (ILIR), Output Loop Impedance Ratio (OLIR) and Voltage Ratio (VR) for determining recharging current transmission efficiency. Two methods for enhancing recharging current transmission efficiency have been proposed: those are impedance method and voltage method. According to the implantable battery recharging condition derived from circuit analysis, it is concluded that square wave is the best one for exciting external electrodes in energy delivery based on volume conduction.According to the circuit analysis results, a circuit prototype based on volume conduction had been developed. In our preliminary experiment, it had delivered a 5 kHz current of up to 2.8 mA across freshly harvested pigskin with a current transmission efficiency of 27%.Theoretical analyses and experiments have proved that electrical energy can be transformed efficiently from an external body into implantable devices in the body through volume conduction.更多还原