高强度聚焦超声换能器温度场的数值仿真

摘要

相控阵高强度聚焦超声换能器可以通过换能器上不同阵元发射超声波的时间不同来实现变焦、多焦点.该论文应用Westervelt方程的近似式,结合Pennes热传导方程,以人体乳房为例,FDTD(finite difference time domain)仿真对比研究平面阵列相控聚焦换能器与曲面阵列相控聚焦换能器形成温度场的特性,同时数值仿真研究不同占空比的正弦激励函数、不同治疗频率、声强对曲面阵列相控聚焦换能器超声温度场的影响.研究结果表明曲面阵列相控聚焦换能器能有效地减少皮肤处的温升,对皮肤的伤害较小;对于曲面阵列相控聚焦换能器,不同占空比的正弦激励函数形成的可治疗区域(60℃以上)大小差别不大,但最高温度不同;随着频率升高,形成的可治疗区域体积减小;随着输入声强的增大,可治疗区域变大,但焦距不变.%High Intensity Focused Uitrasound (HIFU) phased array transducer is capable of obtaining vari-focus and multiple-focus by application of different ultrasound timetables launched by different elements.In this paper,a numerical method of temperature field based on Westervelt equation and Pennes Bio-heat conduction equation was shown by taking the 3D breast tissues model as an example for analyzing the plane phased array transducer (PPAT) and the spherical-section phased array transducer (SSPAT).Here,aRer having comparatively examined temperature field formed of the PPAT and the SSPAT,temperature field is also did that formed at difierent sine excitation with vailable duty cycle,frequency and sound pressure intensity by the SSPAT.The simulation results obtained by the present method showed the temperature rise on the skin and the temperature field in focus region.The results illustrated that using SSPAT could reduce skin temperature significantly and cause less skin bums.These also turned out that the size of focal regions (with a temperature of 60℃ or above) that formed by excitation functions of different duty cycle ale nearly the same,while the peak temperature rise different.In addition.the focal regional size was proportional to the ultrasound power densities, inversely proportional to the frequency and without a conspicuous fluctuation of focal distance.