DEVELOPMENT OF A PORTABLE EXTRACORPOREAL LITHOTRIPTER USING A NEW PIEZOCERAMICS

为了开发一种使用压电陶瓷的原始体外碎石机，对以下主题进行了系统研究。一个新开发的原型机目前正在临床试验，其初步结果表明，未来的实际应用是令人满意的。1）在体外基础实验：作为第一步，大片式压电陶瓷元件作为冲击波发生器的开发。然而，焦点中的峰值压力太小（200巴），无法破坏石头。经过几次改进，最终开发出24件式元件（峰值压力1500 bar，焦点区域2x 19 mm）。对于结石定位，采用了超声诊断系统。在超声观察下，病灶区出现强回声区。研究了高回声区的起源，结果表明，声空化泡可能是其产生的原因。2）动物实验：将人肾结石或模型肾结石植入犬肾，体外碎石。结石被满意地撑开，安全可靠。显微镜观察显示，聚焦冲击波暴露时，肾组织损伤发生在聚焦区域。3）原型碎石机的临床应用：超声诊断系统能正常检出结石。初步结果显示，结石清除率为52%，预计24%的患者可自行通过。33例患者总有效率为76%，术后均出现3 ~ 5次血尿，无其他严重并发症。试验结果表明，该装置具有良好的破坏性和安全性，适合于实际应用。

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.