Li Jun-Lun, Liu Xiao-Zhou, Zhang Dong, Gong Xiu-Fen
Key Laboratory of Modern Acoustics, Ministry of Education, Institute of Acoustics, Nanjing University, Nanjing, China.
Ultrasound Med Biol. 2007 Sep;33(9):1413-20. doi: 10.1016/j.ultrasmedbio.2007.05.001. Epub 2007 Jul 13.
This article theoretically and experimentally studies the influence of ribs on the nonlinear sound field in ultrasound thermal therapy. A three-dimensional (3-D) numerical algorithm is developed to solve the Khokhlov-Zabolotaskaya-Kuznetsov equation in the frequency domain for description of the asymmetrical nonlinear ultrasound field. Two kinds of rib configurations are used to simulate the typical situations in the therapeutic treatment of liver tissues. Both numerical simulations and experimental measurements are made to evaluate the effect of the rib cage on the nonlinear ultrasound field. Results indicate that (1) when the ultrasound propagates through the space between the ribs, the position of the maximum amplitude of the fundamental component is shifted toward the transmitter surface up to 20 mm in some configuration; the maximum sound intensity can be either enhanced to 106% or decreased to about 20% compared with the value in the free field and the beam width in situ is affected by the sound diffraction; and (2) in the case of a rib positioned in the way of ultrasound propagation, the sound energy is significantly decreased and severe interference is observed. Satisfactory agreement between the theoretical prediction and measured results demonstrates the validity of the theoretical model and its solution.
本文从理论和实验两方面研究了肋骨对超声热疗中非线性声场的影响。开发了一种三维（3-D）数值算法，用于在频域中求解霍克洛娃-扎博洛塔斯卡娅-库兹涅佐夫方程，以描述非对称非线性超声场。使用两种肋骨配置来模拟肝脏组织治疗中的典型情况。通过数值模拟和实验测量来评估肋骨对非线性超声场的影响。结果表明：（1）当超声在肋骨间的空间中传播时，在某些配置下，基波分量最大振幅的位置会向发射器表面偏移达20毫米；与自由场中的值相比，最大声强可增强至106%或降低至约20%，且原位波束宽度受声衍射影响；（2）在肋骨位于超声传播路径上的情况下，声能会显著降低，并观察到严重干扰。理论预测与测量结果之间的良好一致性证明了理论模型及其解的有效性。
