Analysis of cavitation induced stresses on blood vessel wall during photo-mediated ultrasound therapy using finite-element based numerical models

Abstract

Photo-mediated ultrasound therapy (PUT) is a novel technique, which utilizes spatio-temporally synchronized pulsed laser and ultrasound to produce enhanced cavitation inside blood vessels. Vascular bio-effects during PUT, such as reduced perfusion rate and rupture of blood vessel, are thought to be due to shear and circumferential stresses induced on vessel wall. We have developed a 2D axisymmetric and a 3D finite-element method (FEM)-based models in COMSOL Multiphysics to calculate the stresses induced on vessel wall during PUT. The 2D axisymmetric model simulation showed that drastic increase in bubble size with PUT application resulted in higher shear and circumferential stresses as compared with ultrasound application only in the beginning phase of PUT. The 3D model simulation showed increase in stresses when a bubble moves towards the vessel wall, and found relatively higher increase in shear stress as compared to circumferential stress. The 2D results were imperative in understanding of PUT inception resulting in stronger stresses on vessel walls, which were otherwise almost zero for ultrasound-only. The 3D results demonstrated that the stresses on vessel walls further increased during the subsequent phase of PUT, enough to induce vascular bio-effects.