In vitro validation of three-dimensional cavitation-based pressure mapping for quality assessment of clinical high intensity focused ultrasound devices.

Abstract

Sufficiently robust and reliable quality assessment (QA) procedures are vital in assuring the widespread adoption of high intensity focused ultrasound (HIFU) for use in both thermal ablation and enhanced drug delivery. Mapping of broadband cavitation emissions in a tissue-mimicking material with a repeatable cavitation threshold offers the potential for rapid, 3-D, cavitation-based pressure mapping of the field produced by a given HIFU transducer. Previous work has demonstrated the viability of this concept, including the design and optimization of a 50-element, cylindrical array capable of mapping a collection of broadband sources distributed throughout a region comparable to the size of a typical HIFU focal volume. The work presented here relates to in vitro experimentation using the array to map cavitating fields produced by a number of HIFU transducers at a range of insonation amplitudes. Results are compared to the predicted size of the cavitation region determined via hydrophone-based characterizations of the HIFU field. Future work will involve using the array to map the instigation and evolution of cavitating fields in three-dimensions in ex vivo tissue during HIFU exposure.