高强度聚焦超声治疗中基于电阻抗相对变化的组织温度监测技术

Relative Electrical Impedance Variation Based Temperature Monitoring Technology for High Intensity Focused Ultrasound Therapy

高强度聚焦超声(HIFU)通过聚焦超声的声热效应对肿瘤组织进行局部快速的热疗,是一种非侵入性的无创肿瘤治疗新技术,而其治疗过程中温度监测是HIFU治疗中剂量精准控制的关键.本文基于HIFU的声传播基本原理,建立了HIFU治疗和组织电阻抗测量的模型,数值模拟了治疗过程中焦域的声场、温度场和电导率分布,并通过电势和电流密度分布的变化,计算了模型的电阻抗的整体变化,结果表明在一个规定的HIFU声功率作用下,组织模型的电阻抗相对变化和治疗时间呈线性关系,其电阻抗相对变化率和HIFU声功率也呈线性关系.按照仿真条件,建立了HIFU治疗和电阻抗实时测量的联合实验系统,在不同声功率和治疗时间条件下,对组织模型的电阻抗相对变化进行了测量,实验结果和理论仿真结果基本一致.研究结果证明用电阻抗相对变化进行HIFU治疗中焦域温度监控的可行性,为其疗效检测和剂量控制提供了新方法.

High intensity focused ultrasound（HIFU）can kill the tumor cells with the acousto-thermo-coagulation effects in the focal region,and it is considered to be the noninvasive technology for therapy. Based on the principle of acoustic trans-mission for HIFU,a composite model of HIFU therapy and electrical impedance measurement is established. Numerical studies for the distributions of the acoustic,temperature and conductivity fields in the focal region are conducted and the relative variations of the electrical impedance of the model are also achieved. It is proved that,for a fixed acoustic power, the relative impedance variation（ RIV） shows a linear relationship with the treatment time and the rate of RIV increases linearly with the increase of the acoustic power.With the experimental setup,the measurements of the electrical impedance of the model are performed during the HIFU therapy,and good agreements to the simulation results are achieved. The favorable results verify the feasibility of noninvasive temperature monitoring using the RIV and also provide a new method for efficacy detection and dose control for HIFU therapy.