Bio-acoustic thermal lensing and nonlinear propagation in focused ultrasound surgery using large focal spots: a parametric study
Bio-acoustic thermal lensing and nonlinear propagation in focused ultrasound surgery using large focal spots: a parametric study
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DOI：
10.1088/0031-9155/47/11/306
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发表时间：
2002-06-07
影响因子：
3.5
通讯作者：
Hynynen, K
中科院分区：
文献类型：
--
作者：
Connor, CW;Hynynen, K
众所周知，软组织的声学特性与组织温度有关。这在聚焦超声手术中特别有趣，因为聚焦超声手术的作用机制是通过超声吸收诱导局部加热来杀死目标组织，从而烧灼该组织。然而，局部加热的行为会引起目标组织及其周围组织的声学特性的变化。这种现象使入射声波前变形，因此被称为热透镜效应。此外，声学传播中的非线性效应在治疗作用所需的超声强度下变得不可忽略。本文通过模拟各种临床应用的相控阵换能器配置来研究热透镜效应和非线性组织特性的重要性，这些配置尚未使用声学传播的全三维非线性处理进行适当分析。通过对比声热耦合模拟与不耦合模拟，说明了热透镜效应的重要性；忽略热透镜通常会产生1到2毫米的运动，在预测的焦点位置向传感器。结果还表明，在某些临床相关的换能器配置下，经典的声传播方法可能产生严重错误的结果，并且用水听器进行声场扫描可能无法准确预测治疗效果。
It is well known that the acoustic properties of soft tissue have a dependence on tissue temperature. This is of particular interest in focused ultrasound surgery since the mechanism of action of focused ultrasound surgery is to kill targeted tissue by inducing localized heating by ultrasound absorption, and hence cautery of that tissue. However, the act of localized heating induces a change in the acoustic properties of the targeted tissue and tissue surrounding it. This phenomenon distorts the incoming acoustic wavefront, and has been termed the thermal lens effect for this reason. Furthermore, nonlinear effects in acoustic propagation become non-negligible at the ultrasound intensities required for therapeutic action.This paper examines the importance of the thermal lens effect and nonlinear tissue properties by simulating a variety of clinically applicable phased array transducer configurations that have not yet been appropriately analysed using a full three-dimensional nonlinear treatment of acoustic propagation. The significance of the thermal lens effect is characterized by comparing the simulation of coupled acoustic and thermal propagation with an uncoupled treatment; neglecting thermal lensing typically produces a movement of 1 to 2 mm in the predicted position of the focus towards the transducer.The results also show that the classical methods of acoustic propagation can produce grossly erroneous results under certain clinically relevant transducer configurations and that an acoustic field scan with a hydrophone may not accurately predict therapeutic effect.