Development of a tomographic cavitation sensor for quality assessment of clinical high intensity focused ultrasound systems.

Abstract

High‐intensity focused ultrasound (HIFU) fields are known to nucleate and excite inertial and noninertial cavitation in tissue and tissue‐mimicking materials once a threshold negative acoustic pressure is reached. In the context of ablative HIFU treatment, inertial cavitation has been correlated with significantly enhanced rates of heating, while in histotripsy, cavitation is the very mechanism that causes tissue damage. Characterizing the extent of the cavitation region produced by clinical HIFU devices is therefore important to ensure safe, efficient, and effective treatment. A novel, multielement sensor is being developed to enable accurate axial and radial mapping of the cavitation region during HIFU exposure by passive detection and tomographic reconstruction of the broadband emissions arising from bubble collapse. Computational modeling has shown that the application of a cross‐correlation algorithm to simulated received signals has the potential to localise individual sources of emissions with submillimeter accuracy. Initial experimental validation of models has been conducted using a prototype device developed in collaboration with the National Physical Laboratory. Future work will involve the refinement of the sensor design and reconstruction algorithm to improve spatiotemporal resolution, along with the development of a tissue mimicking material which matches the acoustic properties and cavitation threshold of real tissue.