BACKGROUND:Exploration on nonlinear acoustic response of the contrast agent microbubble contained in microvessel under ultrasound excitation is of great significance to maximizing ultrasonic energy deposition, promoting the development of quantitative imaging algorithm, revealing the damage mechanism or evaluating the targeted therapy, and overcoming the limitations of the traditional methods that are mainly used in large-size vessels, and measuring microvessel elasticity.
OBJECTIVE:To build a microvessel containing an ultrasound microbubble, revealing the internal mechanism among ultrasound, microbubble, blood flow and microvessel.
METHODS:Based on the finite element analysis and the lumped parameter model, three-dimensional microvessel containing microbubble model was built and simulated on Comsol Multiphysics 4.4 platform.
RESULTS AND CONCLUSION:Microbubble exhibited slower radial motion compared with axial motion due to vascular wal limitation, but maximum displacement and stress were found near the microbubble center because of the oscil ation coupling of the microbubble with the vascular wal . Under the same ultrasound pressure, the excitation frequency increased, accompanied by decreased and stabilized microvessl constriction and dilation;under the same frequency, with the enhancement of ultrasound pressure, the local microbubble oscil ation lasted longer. With the increase of Young’s modulus of the microvessel wal , the frequency of microbubble oscil ation was reduced, while the amplitude increased. Al these findings indicate that the frequency of microbubble oscil ation increased with the reduction of microvessel size, while its amplitude decreased. The frequency of microbubble oscil ation increased with the enhancement of ultrasound excitation, while the amplitude decreased. On the contrary, ultrasound pressure affected the dynamic characteristics of microbubble and microvessel. In particular, it was the first to demonstrate that the elasticity of microvessel has approximate linear positive correlation with the amplitude of microbubble oscil ation, which reveals the relationship between microvessel elasticity and microbubble response so as to provide theoretical basis for indirect measurement of microvessel elasticity.