Modeling And Simulation Of Dynamics Of Microvessel Containing Microbubble In Ultrasound Field

Contrast agent microbubble imaging has manifested distinctive value in disease diagnosis, treatment, and hemodynamic measurement. It is a crucial task to reveal the relationship between the microbubble and the complex surrounding physiology environment, and the nonlinear acoustic response characteristics of the microvessel. It will provide the important theoretical basis for microbubble-based quantitative imaging, detection of early vascular disease, and ultrasound microbubble targeting therapy.The lumped-parameter model was the theoretical basis of this study, including the model assumption, blood flow, microbubble dynamics, vascular deformation and boundary conditions. It was applied to describe the multi-field coupling model of microvessel containing microbubble in ultrasound field, so as to investigate the interaction between the microvessel, blood flow and microbubble. The COMSOL Multiphysics software was adopted to reveal the qualitative and quantitative relationships between microbubble oscillation and microvessel structure and wall elasticity.The experimental results were obtained:(1) The frequency of microbubble oscillation increased with the increase of the excitation ultrasound frequency, while the amplitude changed in the quite contrary. The intensity of contracting and expanding of the microvessel reduced with the increase of reduction of the excitation ultrasound frequency, whereas, the excitation ultrasound pressure had the opposite affects on the microbubble and microbubble;(2) The microvessel size(length, diameter and wall thickness) was smaller, the restriction on the microbubble was stronger, the frequency and amplitude of microbubble oscillation was bigger, and vice versa;(3) Young’s modulus and Poisson’s ratio of wall increased, frequency of microbubble oscillation increased accordingly, but its amplitude decreased.(4) With the increase of microbubble radius, the amplitude and frequency of contracting and expanding of the microvessel increased. In particular, it was the first time to demonstrate that the elasticity of the microvessel wall was approximate linear positive correlative with the amplitude of the microbubble oscillation. This study has valuable potentials to determine the optimum ultrasonic irradiation conditions, measure the microvessel wall elasticity, evaluate the safety of microbubble in the body, guide and develop the ultrasound targeted therapy.