猪肝脏灌流对脉冲高强度聚焦超声辐照致热沉积的影响

摘要

Objective To observe the impact on thermal deposition for in vitro pork liver exposed to pulsed high intensity focused ultrasound (pHIFU).Methods A circulated and a non-circulated pork liver were exposed to pHIFU for 20 s at a 20 mm depth,respectively,pHIFU was maintained at 80 W acoustic power,100 Hz pulse repetition frequency.The duty cycles were 40％,30％ and 20％.After 10 repeated pHIFU irradiations under every parameter,all 60 exposures were performed,with 30 in the circulated liver and the other 30 in the non-circulated liver.During pHIFU exposures,the temperatures in the focal region were detected using a thermocouple embedded into the liver.B-mode ultrasonic images were also collected at the moment after irradiations,and the area of hyperecho regions were calculated.After all irradiations,the livers were sliced into 1-2 mm,and the maximum lesions were photographed.Then,the volumes of the pictured necrosis were computed.Results During all pHIFU exposures,compared to non-circulated liver,the temperature raised slowly and the mean peak temperatures were significantly smaller in the circulated liver (P＜0.05).After the circulated liver exposed to pHIFU,less hyperecho regions and necrosis area were observed in the circulated liver (P＜0.05).However,the values of increased echoes in B-mode ultrasonic images were very nearly the same after the two liver irradiations.Conclusion The thermal deposition in pork liver tissues around vessels decreases because of circulation of blood flow during pHIFU irradiation.%目的 以离体猪肝脏灌流模型探讨脉冲高强度聚焦超声(pHIFU)辐照下血流对热沉积的影响.方法 采用pHIFU以定点方式辐照离体再灌注猪肝组织和非再灌注猪肝,辐照功率为80 W,辐照深度20 mm,脉冲重复频率为100 Hz.占空比为40％、30％、20％,辐照时间均为20 s.于每组参数下重复辐照10次,共60个辐照点(再灌注组30个辐照点与非再灌注组30个辐照点).辐照中使用热电偶测量靶区温度.辐照后即刻采集B超声像图,计算灰度增强区域的面积.辐照结束后,将猪肝切成厚为1～2 mm薄片,找出最大损伤所在层面,测量猪肝实际坏死体积.结果 各参数辐照下,离体再灌注猪肝中靶区温升均慢于非再灌注猪肝,且平均最高温度低于非灌注猪肝(P＜0.05).辐照后即刻,pHIFU辐照再灌注所致声像图中灰度增强区域的面积小于非再灌注猪肝(P＜0.05),但平均灰度变化值差异无统计学意义.辐照结束后,pHIFU所致再灌注猪肝中的坏死体积小于非灌注猪肝.结论 灌流条件下,血流循环的存在使pHIFU辐照所致血管周围猪肝组织中的热沉积减小.