Spatiotemporal quantification of therapeutically relevant cavitation for ablation and drug delivery by ultrasound

• Published in: Journal of the Acoustical Society of America 2012-04, Vol.131 (4)
• Main Authors: Rifai, Bassel, Gyongy, Miklos, Choi, James, Ritchie, Rob, Hockham, Natalie, Collin, Jamie R.T, Mylonopoulou, Eleonora, Jensen, Carl, Coussios, Constantin-C
• Format: Article
• ISSN: 0001-4966; 1520-8524

Stable and inertial cavitation have been shown to play a key role in several therapeutic ultrasound applications, ranging from non-invasive ablation to drug delivery. In order to achieve meaningful quantification of therapeutically relevant cavitation, a hypothesis as to the underlying mechanism by which bubbles enhance energy delivery and momentum transfer to their surroundings must first be formulated. Based on this hypothesis, correlations can be sought between time-based or frequency-based metrics of a relevant cavitation 'dose' and the desirable associated bioeffects, enabling the establishment of thresholds for therapeutically relevant processes to occur. However, the problem is complicated further by the fact that a single type of cavitation activity rarely occurs throughout an ultrasound exposure, or throughout the acoustic field of a therapeutic transducer. A recently developed method, known as passive acoustic mapping, makes it possible to obtain real-time maps of inertial and stable cavitation activity and could thus enable improved dosimetry of therapeutically relevant cavitational processes. The use of passive acoustic mapping for spatiotemporal classification and quantification of cavitation will be illustrated in the context of HIFU ablation, drug release from thermosensitive liposomes and drug delivery.