通过测量组织体模瞬时温升描述HIFU声场特征

 针对高声压下高强度聚焦超声（High Intensity Focused Ultrsound,HIFU）声场测量难题，提出通过测量组织体模中瞬时温升来描述HIFU声场特征的方法。采用水听器测量声功率为5W的HIFU声场分布；采用热电偶测量声功率为40、70、100、150、200W，辐照时间1s下HIFU作用于组织体模时的焦域温场分布，由瞬时温升■与■αi p2i 成正相关关系，得到在考虑声吸收系数改变和非线性条件下HIFU声场分布特征。结果显示，水听器测量得到的HIFU焦域径向-6dB宽度和轴向-6dB宽度，远小于通过热电偶检测得到的不同高功率下HIFU焦域径向和轴向大小；高功率下，随声功率增加，焦域径向-6dB宽度、轴向-6dB宽度逐渐增大，且温场分布图的峰值部分较尖，反映出能量比较集中。用热电偶测量组织体模焦域瞬时温升，能反映在考虑声吸收系数改变和非线性条件下HIFU声场分布特征。

Measuring Instantaneous Temperature Rise in Tissue Phantom to Describe Sound Field Characteristics of High Intensity Focused Ultrasound

In view of the difficulty in the measurement of High Intensity Focused Ultrsound(HIFU) at high pressure, this paper presents a method of characterization of the sound field of HIFU by measuring the instantaneous temperature in a tissue phantom. The HIFU field in water is measured by using hydrophone when the power is 5W. The temperature distribution of the focal region in tissue phantom with the HIFU exposure time of 1 second, is measured by using thermocouple, with expected US power of 40，70，100，150 and 200W, respectively. The instantaneous temperature rise and the acoustic pressure are positively correlated through the sound absorption coefficient and the HIFU field nonlinear characterization is obtained through the variations of the sound absorption coefficient. The results show that the -6dB width of the radial focal region and the axial focal region measured by Hydrophone is much smaller than the radial and axial size focal region obtained by thermocouple under different high-power HIFU; under high power,as the power increase,the -6 dB width of the radial focal region and the axial focal region gradually changes, and the peak of the temperature field distribution is more pointed, reflecting the fact that the energy is more concentrated.