高强度聚焦超声场中空化泡群的结构及其形成过程

Cavitation bubble structure and its formation process in high-intensity focused ultrasound field

空化是高强度聚焦超声(HIFU)引起组织损伤的作用机制之一。本文使用高速摄影技术研究了HIFU场中空化泡群结构的空间分布特征、超声功率对空化泡群结构的影响、空化泡群结构的建立过程尤其是起始过程。空化泡群的结构以空化泡在声场中的区域化分布为特征．在一定功率范围内空化泡群的结构保持稳定。从建立过程来看,空化泡群首先出现在焦区,然后在焦后区(远离换能器的区域)形成,焦前区(靠近换能器的区域)空化泡群最后形成。在对空化泡群起始的研究中发现最初拍摄到的空化泡群形状与焦区形状接近,并且观察到空化泡在焦区发生聚集然后破裂的现象。

Cavitation is one of the mechanisms that lead to tissue erosion by high intensity focused ultrasound （HIFU）. High-speed photography was used to study spatial distribution characteristics of cavitation bubble cloud structure in HIFU field, the influence of ultrasonic power to the structure, and its formation process with special attention to its inception process. The structure of the cavitation bubble cloud is featured by the regional distribution of cavitation bubbles. Within a range of ultrasonic power levels the structure remains stable. In terms of its formation process, cavitation bubble cloud first emerges in the focal region, then appears in the post-focal region （far from the transducer） and finally forms in the pre-focal region （near to the transducer）. During the inception process of the cavitation bubble cloud, the initial photographed bubble cloud is approximately the same shape as the focal region, and cavitation bubbles are observed to coalesce and collapse in the focal region.