相控阵激励信号对经颅HIFU焦域影响的仿真研究

Numerical simulation of the effect of driving signals by phased transducer on transcranial focal region

目的:研究相控阵激励信号对高强度聚焦超声(HIFU)经颅骨聚焦形成焦域的影响,解决HIFU经颅聚焦焦点偏离并对颅骨及其周边组织造成热损伤的问题。方法:基于时间反转法提出利用互相关关系调制阵元激励信号相位及幅值的方法,根据临床实际建立人头颅CT数据和相控阵的三维头颅数值仿真模型,以时域有限差分法数值仿真HIFU经颅形成的声压及温度场,分析相控阵激励信号对HIFU经颅形成焦域的影响。结果:通过调制相控阵激励信号的相位,可使HIFU在设定焦点处聚焦;通过调制激励信号的幅值,可使焦点处最大声压和最高温度升高;通过调制不同环阵元激励信号的幅值,可降低聚焦时颅骨处的温度。结论:调制相控阵激励信号可实现经颅HIFU精准高效聚焦,增大在焦点处的声能量聚积;调制不同环阵元激励信号的幅值,可降低颅骨的温度,防止对颅骨周边组织造成热损伤。

Objective：To investigate the effect of driving signals by phased transducer arrays on the transcranial focal region and to solve the problem of transcranial defocusing and thermal damage to the skull and tissue around it. Methods：Method was put forward by modulating phase and amplitude of driving signals based on the time reversal and cross-correlation among signals. A numerical simulation model was established based on skull CT data and phased transducer. The finite difference time domain method was used to simulate the distribution of transcranial HIFU pressure and temperature fields to study the influence of driving signals by phased array on transcranial HIFU focal region. Results：Results of numerical simulation indicated that focus was formed accurately at the target by modulating the phase of driving signals of transducer arrays;the maximum pressure and temperature at focus were increased by modulating the amplitude of driving signals by transducer arrays;temperature in skull was decreased by modulating the amplitude of different arrays of transducer. Conclusion：By modulating driving signals of phased array, we can achieve precise and effective transcranial focusing and the acoustic energy deposited at focus would increase. By modulating driving signals of different arrays, temperature decreases in skull thus avoiding thermal damage to skull and the surrounding tissue.