Image-based computational model for focused ultrasound ablation of liver tumor

Abstract

High-intensity focused ultrasound (HIFU) is a rapidly developing medical technology that allows non-invasive thermal ablation of tumors. Thermal treatment of liver tumor, which is one of the most common malignancies worldwide, is problematic because large blood vessels act as a heat sink. Convective cooling protects the cancer cells from thermal destruction and decreases the necrosed volume. A major objective of the method development is to achieve a virtually complete necrosis of tumors close to major blood vessels and to avoid blood vessel damage and, hence, the needed treatment planning. The present study is aimed at predicting liver tumor temperature during HIFU thermal ablation in a patient-specific liver geometry. The model comprises the nonlinear Westervelt equation and bioheat equations in the liver and blood vessels. The nonlinear hemodynamic equations are also taken into account with the convected cooling and acoustic streaming effects being taken into account. We found from this three-dimensional three-field coupling study that in large blood vessels, both convective cooling and acoustic streaming may change the temperature considerably near the blood vessel. More precisely, acoustic streaming velocity magnitude can be several times larger than the blood vessel velocity. The results presented in the current work can be further used to construct a surgical planning platform.

Temperature elevation by HIFU inex vivoporcine muscle: MRI measurement and simulation study

“…Gas bubbles are formed in the focal area and this region can be seen as an echogenic region. Treatment planning [10][11][12][13] becomes therefore very important for US imaging. Before the treatment acoustic parameters of the transducer should be well adjusted in the case of US guided focused ultrasound therapy.…”

Numerical study of high‐intensity focused ultrasound (HIFU) in fat reduction

“…To obtain the acoustic pressure, the nonlinear propagation equation (Westervelt) of the ultrasonic waves is used. The following full‐wave Westervelt equation, which is based on the effects of diffraction, absorption, and nonlinear propagation, is used 19–25 : $$$$\begin{equation}{\nabla }^2p - \frac{1}{{{c}^2}}\frac{{{\partial }^2p}}{{\partial {t}^2}} + \frac{\delta }{{{c}^2}}\frac{\partial }{{\partial t}}({\nabla }^2p) = \frac{\beta }{{{\rho }_0{c}^4}}\frac{{{\partial }^2}}{{\partial {t}^2}}\left( {{p}^2} \right)\ \end{equation}$$$$ $$$$\begin{equation}\delta = \frac{1}{{{\rho }_0}}\left( {\frac{4}{3}\mu + {\mu }_B + \frac{{\left( {\gamma - 1} \right)k}}{{{c}_p}}} \right)\end{equation}$$$$where p , c , ρ , and δ are the acoustic pressure, speed of the sound propagation in the medium, density, and the diffusivity of sound (Equation 2), respectively, and β $$( {1 + \frac{B}{{2A}}} )$$ is a nonlinearity coefficient. In Equation (2), μ , μ B , γ , k , and c p are the dynamic viscosity coefficient, the bulk viscosity coefficient, the heat capacity ratio, the thermal conductivity, and the specific heat capacity, respectively.…”

Numerical analysis of thermal response of tissues subjected to high intensity focused ultrasound

“…The third term represents attenuation due to thermal conductivity and fluid viscosity. The last term describes the acoustic nonlinearity, which explains the distortion of a wave due to the nonlinear effects and affects the thermal and mechanical changes inside the tissue medium [21].…”