凹球面双频聚焦超声声场的线性声学分析

在线性声学条件下,研究了差频相干模式下的双频聚焦声场的空间-时间特性,分析了换能器分割面积、不同频差对声场的影响.通过计算两波在不同初始相位时轴上瞬时声压起伏的周期性变化规律,证明其合成声场是统计平稳和均匀的.结果表明,适当选择分割面积比和频差,双频声场的"损伤声焦域"相对于单频有明显扩大,并在离体牛肝的损伤实验中得到初步验证,为双频高强度聚焦超声(HIFU)换能器的设计及提高治疗效率提供参照.

Linear Acoustic Analysis of Concave Sphere Dual-frequency Focused Ultrasonic Field

The spatial and temporal characteristics of dual-frequency focused acoustic field of the differential frequency coherence mode were investigated in this paper under the linear acoustic condition, and the effect of partition area of HIFU transducer and various frequency differences on the dual-frequency HIFU acoustic field were also analyzed. It was proved that the composite sound field was smooth and uniform by calculating the periodic variational regularity of the fluctuation of instantaneous sound pressure generated by two waves at difference initial phases. The result indicates that with the proper choice of partition area proportion and frequency difference, the injury sound focal region of dual-frequency acoustic field is larger than that of a single frequency significantly. That has been preliminarily validated by the ex-vivo experiment of cattle liver ablation. It provides a reference to the design of dual-frequency focused transducer and the enhancement of treatment efficiency.