Applications, mechanisms and real-time monitoring of enhanced drug transport by sustained inertial cavitation

Sustained inertial cavitation seeded by microbubbles, sub-micron cavitation nuclei or even without any cavitation nucleation agent has been shown to enable increased delivery and penetration of drugs and vaccines across the skin, into solid tumours and across the blood-brain barrier. The safety and efficacy of these applications are typically monitored using single-element passive cavitation detectors, or more recently using multi-element arrays that enable real-time passive acoustic mapping of cavitation activity. We will provide an overview of the different types of cavitation nucleation agents which are available to use, the type and persistence of acoustic emissions that they are typically associated with, and, where possible, a direct comparison between the performance of different nucleation strategies to achieve the desired drug delivery bioeffect in the target of interest. We will then turn our attention to the presently available strategies for real-time monitoring of safety and efficacy, with specific reference to the benefits offered by the ability to achieve spatiotemporal monitoring of cavitation activity to correlate it with bioeffects in subsets of the overall region of interest.