Numerical Simulations of Ablation Mechanisms during Focused Ultrasound Therapies*

Focused ultrasound therapies such as histrotripsy or burst-wave lithotrispy are promising techniques for non-invasive stone comminution and tissue erosion. Such treatments effectively deliver acoustic energy to a target (such as renal calculi) inside the body with limited impact on surrounding tissue. They involve two important ablation mechanisms. First, the focused ultrasound itself can cause high stresses in the target, particularly as it resonates across a stone. Second, the acoustic energy can cause cavitation bubbles to form near the target, the violent collapse of which induces stone or tissue ablation. Our implementation of a hypoelastic material model in the open-source Multi-component Flow Code (MFC) enables the simulation of each mechanism by modeling the elastic response of stones along with the background fluid dynamics. Simulations of the stresses generated in stones due to focused ultrasound waves and the collapse of bubbles that form near the surface help elucidate the relative impact of each mechanism. To understand this relative impact, we present high resolution simulations of acoustic wave-bubble-elastic solid interactions, enabled by the GPU implementation of the code.