Curra F P, Mourad P D, Khokhlova V A, Cleveland R O, Crum L A
Appl. Phys. Lab., Washington Univ., Seattle, WA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2000;47(4):1077-89. doi: 10.1109/58.852092.
The results of this paper show-for an existing high intensity, focused ultrasound (HIFU) transducer-the importance of nonlinear effects on the space/time properties of wave propagation and heat generation in perfused liver models when a blood vessel also might be present. These simulations are based on the nonlinear parabolic equation for sound propagation and the bio-heat equation for temperature generation. The use of high initial pressure in HIFU transducers in combination with the physical characteristics of biological tissue induces shock formation during the propagation of a therapeutic ultrasound wave. The induced shock directly affects the rate at which heat is absorbed by tissue at the focus without significant influence on the magnitude and spatial distribution of the energy being delivered. When shocks form close to the focus, nonlinear enhancement of heating is confined in a small region around the focus and generates a higher localized thermal impact on the tissue than that predicted by linear theory. The presence of a blood vessel changes the spatial distribution of both the heating rate and temperature.
本文的结果表明，对于现有的高强度聚焦超声（HIFU）换能器，当存在血管时，非线性效应对于灌注肝脏模型中波传播的时空特性以及热生成具有重要意义。这些模拟基于声传播的非线性抛物方程和温度生成的生物热方程。HIFU换能器中高初始压力的使用与生物组织的物理特性相结合，会在治疗性超声波传播过程中诱导激波形成。诱导产生的激波直接影响焦点处组织吸收热量的速率，而对所传递能量的大小和空间分布没有显著影响。当激波在焦点附近形成时，加热的非线性增强局限于焦点周围的小区域，并且对组织产生比线性理论预测更高的局部热影响。血管的存在会改变加热速率和温度的空间分布。
