DEVELOPMENT OF A PORTABLE EXTRACORPOREAL LITHOTRIPTER USING A NEW PIEZOCERAMICS

为了研制一种新颖的采用压电陶瓷材料的体外碎石机，本文对以下课题进行了系统的研究。一台新开发的样机目前正在进行临床试验，初步结果表明，它可以满足未来的实际应用。1)体外基础实验：作为第一步，研制了一种大片压电陶瓷元件作为冲击波发生器。然而，焦点中的峰值压力太小(200巴)，无法破坏结石。经过几次改进，最终开发出了24件式单元(峰值压力1500巴，焦区2x19 mm)。对于结石靶向，采用了超声诊断系统。超声观察，病灶内可见高回声区。研究了高回声区的起源，结果表明，声空化气泡可能是产生高回声区的原因。2)动物实验：将人肾结石或模型结石植入狗肾，体外碎石。令人满意的是，这块石头被安全地分散了注意力。显微镜观察发现，当暴露于聚焦冲击波时，肾组织损伤发生在焦点区域。3)原形碎石机的临床应用：常规超声诊断系统可以很容易地检测到结石。初步结果显示，结石排净率为52%，可自然排出结石的比例为24%。33例患者总有效率为76%，术后总有3~5次血尿，未见其他主要并发症。结果表明，该机具有较好的破坏性和安全性，适用于实际应用。

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.