Passive Cavitation Detection During Skin Sonoporation

Abstract

Passive cavitation detectors (PCDs) have been effectively employed in high-intensity focused ultrasound (HIFU) and cell sonoporation studies to monitor variations in inertial cavitation activity during the course of ultrasound application. As inertial cavitation is the mechanism responsible for many ultrasound induced bioeffects, this monitoring can provide valuable information in real time about the effectiveness of the ultrasound treatment. Despite the well-established benefits of employing PCD techniques in HIFU and cell sonoporation applications, little attempt has been made to utilize such techniques in the field of low-frequency skin sonoporation. This study presents an attempt to employ a confocal PCD system to monitor inertial cavitation activity during sonoporation in a Franz diffusion cell setup. To determine whether inertial cavitation activity was effectively monitored, the output of the PCD system was compared to the cavitation enhanced transport of caffeine through porcine skin. The correlation between caffeine transport enhancement and PCD response was poor relative to similar correlations presented in the literature. This result should not be seen as an indictment on the concept as the present study was only a first attempt at employing a confocal PCD in a skin sonoporation setup. The authors intend to refine their methodology and repeat the study.