高强度聚焦超声辐照离体牛肝组织后回声与空化、沸腾的关系

目的 高强度聚焦超声(high intensity focused ultrasound,HIFU)辐照离体组织过程中焦域处空化、沸腾与回声强度的关系.方法 采用不同的声功率(50 W、100W、150 W、200 W、250W)辐照新鲜离体牛肝组织5s,辐照深度30 mm.在辐照过程中,使用热电偶组成的测温系统对焦域处的温升进行实时采集.5 MHz接收换能器和Labview软件组成的被动空化检测(passive cavitation detection,PCD)系统对焦域处空化信号进行采集,在Labview平台上对空化信号进行定性和定量分析,观察空化信号随时间的变化规律,并计算累积空化剂量.对比HIFU辐照前后的B超图像,计算焦域处的灰度差值.结果 声功率为50 W和100 W的HIFU辐照时,空化和沸腾均未发生,B超图像上未出现回声变化；声功率150W的HIFU辐照时,空化发生(1/2分谐波和宽带噪声)但无沸腾,累积空化剂量和靶区灰度差值增大,辐照后即刻出现弱回声；声功率200 W的HIFU辐照时,空化和沸腾均发生,累积空化剂量和靶区灰度差值继续增大,辐照后即刻观察到强回声出现；声功率250W的HIFU辐照时,空化和沸腾均发生,累积空化剂量和靶区灰度差值略有增大,观察到“明亮”的强回声出现.除声功率为50 W的HIFU辐照后未见凝固性坏死产生,其余各声功率组均产生了凝固性坏死.结论 空化在HIFU辐照后即刻回声的出现中有贡献,但强回声的出现来自于沸腾.

Relationship of Cavitation, Boling and Echo after High Intensity Focused Ultrasound Exposure in Ex Vivo Tissue

Objective To explore the relationship between cavitation, boling and echo after exposed immediately in the focal region during high intensity focused ultrasound exposure in ex vivo tissue. Method Using different acoustic power （50 W, 100 W, 150 W,200 W,250 W） irra- diation of fresh bovine tissue in vitro for 5s,irradiation depth of 30mm. Thermocouple consisting of a temperature measurement system focu- sing field at the real-time temperature rise acquisition. 5 MHz receiving transducer and Labview software consisting of a passive cavitation de- tection （PCD） system focusing field at the cavitation signal passive cavitation detection, qualitative and quantitative analysis of cavitation sig- nal in Labview platform,observe the cavitation signal variation with time, as well as calculate the cumulative cavitation does. Contrast the B ultrasonic images before and after HIFU irradiation to calculate the changes of the focal region at the gray. Results When the power of 50 W andl00W was not observed cavitation activity and boling, without changes of gray level difference of the focal region on B-mode ultrasound image, when the power of 150 W was observed cavitation actiyity（ 1/2 harmonic and broadband noise） but no boling,With increase of gray level difference and the accumulated cavitation does＇, echo began to appear, when the power of 200W was observed cavitation activity and bo- ling, with continued increase of gray level difference and the accumulated cavitation does, the hyperecho was observed, when the power of 250 W was observed cavitation and boling, with slight increase of gray level difference and the accumulated cavitation does, observed ＂bright＂ hy- perecho. The coagulation necrosis was, seen in all bovine livers except 50W after the exposures. Conclusions Cavitation contribute to the e- mergence of echo after exposed, but the hyperecho is mainly due to boiling after irradiation immediately.