Numerical study of the interaction between focused ultrasound wave and brain-like soft material

Focused ultrasound is of great significance in the fields of medical ultrasound imaging, diagnosis, and treatment, yet little is known about the quantification of the physical effects of focused ultrasound and the analysis of the corresponding biological effects. In this paper, the acoustic-solid-thermal coupled computational model is developed to study the interaction between focused ultrasound and brain-like soft materials. Firstly, a hyper-viscoelastic constitutive model is established to describe the dynamic and thermal-mechanical behaviour of brain-like soft material. Due to the high compression resistance and low shear resistance of brain-like soft materials, it will appear in the focus area that Compression strain and shear strain are approximate, but compressive stress is much larger than shear stress. Secondly, the dynamic mechanical response of brain-like soft materials under focused ultrasound excitation with different frequencies and amplitudes were studied. By analyzing the hysteresis loop of the feature points in the focus area, it can be concluded that the loss angle of dynamic modulus of brain-like soft materials increases with the increase of load frequency and the increase of load frequency. The higher the load amplitude is, the greater the energy input to the focusing region is, and the faster the dissipation speed is. At last, through the multi-field coupled simulation, it is found that the focusing accuracy of the focused ultrasound increases with the increase of the frequency, but the focusing energy intensity will decrease. The input energy has an optimized value in a specific frequency range. The research is helpful for the improvement of focused ultrasound diagnosis, imaging and treatment technology, and the use of dynamic mechanical property inversion of brain-like soft materials.