DEVELOPMENT OF A PORTABLE EXTRACORPOREAL LITHOTRIPTER USING A NEW PIEZOCERAMICS

为了研制一种新颖的压电陶瓷体外碎石机，本文对以下几个方面进行了系统的研究。新研制的样机目前正处于临床试验阶段，初步结果令人满意，可用于未来的实际应用。1)体外基础实验：作为第一步，开发了一种大块压电陶瓷元件作为冲击波发生器。然而，焦点处的峰值压力太小（200巴），不足以破坏石头。经过几次改进，最终开发出24片元件（峰值压力1500 bar，焦点面积2x19 mm）。结石定位采用超声诊断系统。超声观察下，病灶区出现高回声区。研究了高回声区的起源，结果表明声空化气泡可能是高回声区的产生原因。研究了所施加的冲击波（峰值压力和暴露率）与岩石破坏程度的关系。2)动物实验：将人肾结石或模型结石植入狗肾，体外崩解。那块石头令人满意地分散了注意力，安全可靠。镜下观察发现，在聚焦冲击波作用下，肾组织损伤发生在病灶区。损伤以动脉损伤为主。3)原型碎石机临床应用：常规超声诊断系统可轻松检测出结石。初步结果显示结石清除率为52%，自然通体率为24%。33例患者总有效率为76%，术后常出现3 ~ 5次血尿，无其他主要并发症。结果表明，该机器可用于实际应用，具有良好的破坏性和安全性。

In order to develop an original extracorporeal lithotripter using piezoceramics following subjects have been systematically investigated. A newly developed prototype machine is at present under clinical trial and its preliminary results shows satisfactory for future practical use.1) In vitro basical experiments: As a first step a large-piece piezoceramic element was developed as a shock wave generator. However, a peak pressure in the focus was too small (200 bar) to destruct the stone. Following several improvements, a 24-piece element was finally developed (peak pressure 1500 bar, focal area 2x19 mm). For stone targeting an ultrasonic diagnostic system was adopted. Under ultrasonic observation a hyperechoic region developed in the focal region. Origin of the hyperechoic region was investigated and results indicated that acoustic cavitaion bubbles was probably responsible for its generation. The relationship between the applied shock waves (peak pressure and exposure rate) and the stone destructibility was also investigated.2) Animal experiment: The human renal calculi or a model calculi was implanted in a dog kidney and the stone was extracorporeally disintegrated. The stone was satisfactorily distracted with reliable safety. microscopic observation revealed that the renal tissue injury occurred in the focal region, when exposed to focused shock waves. The injury was mainly attributable to the arterial damage.3) Clinical application of a prototype lithotripter: The stone was easily detected by the ultrasonic diagnostic system as usual manner. Preliminary result showed that a stone-free rate was 52%, and spontaneous passage was expected in 24%. Therefore, total effectiveness was 76% in 33 patients, As a complication 3 to 5 times of hematuria were always observed postoperatively, but no other major complications. The results indicated that the machine was applicable to the practical use with satisfactory destructiveness and safety.