组织声学特性对高强度聚焦超声温度场的影响

目的 数值仿真组织声学特性对高强度聚焦超声（HIFU）焦域处温度场的影响,为HIFU治疗安全性和可靠性提供理论依据.方法 以实测新鲜离体猪肝组织不同温度下的声速和衰减系数为依据,利用时域有限差分（FDTD）法数值仿真研究HIFU治疗过程中组织内声速、衰减系数的变化和温度场的分布,分析讨论声速和衰减系数变化对60 ℃以上可治疗区域大小、位置的影响.结果 随着照射时间的延长,焦域处肝组织温升增大,声速下降,声衰减系数增大.随着声速的变化,形成的可治疗区域变大,焦点位置向远离换能器方向移动;随着声衰减系数的变化,焦域大小和焦点位置几乎不变.结论 猪肝组织内声速的变化对可治疗焦域的位置和大小影响较大;声衰减系数的变化对焦域的影响较小.

Effect of tissue acoustic properties on HIFU temperature field

Objective To improve the safety and reliability in high intensity focused ultrasound(HIFU)therapy, the effects of tissue acoustic properties on the high intensity focused ultrasound temperature field were investigated. Methods Based on the measured data of sound velocity and attenuation coefficient at different temperature, the variation of sound velocity and attenuation coefficient, and the temperature distribution in tissue during HIFU therapy was simulated using FDTD method. Moreover, the effects of the two variable acoustic parameters on the therapeutic region above 60 ℃ were evaluated. Results Tissue temperature raise, sound speed decreased and the attenuation coefficient increased in the focal region, along with the passage of the exposure time. Therapeutic region increased slightly and the focal point slightly moved away from the transducer when the sound velocity varied. There were negligible changes in the therapeutic region and the position of focal point when the attenuation coefficient changed alone in the study. Conclusion The variation of sound velocity can affect the size and location of the focal region in pig liver, while the effect of the attenuation coefficient variation is negligible.