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.