Applications of Acoustics and Cavitation to Noninvasive Therapy and Drug Delivery

Abstract

Biomedical acoustics is rapidly evolving from a diagnostic modality into a therapeutic tool and acoustic cavitation is often found to be the common denominator in a wide range of new therapeutic applications. High-intensity focussed ultrasound (HIFU) waves generated outside the body can be used to deposit heat deep within the body. Through a quantitative analysis of heat deposition by ultrasound, it is shown that inertial cavitation can help address some of the major challenges of HIFU therapy by providing a means of enhancing and monitoring treatment non-invasively. In the context of drug delivery, both inertial and stable cavitation are found to play a role in enhancing drug activity and uptake. In particular, shape oscillations arising during stable cavitation are shown to provide an effective micro-pumping mechanism for enhanced mass transport across inaccessible interfaces.

Enhanced-heating effect during photoacoustic imaging-guided high-intensity focused ultrasound

“…Cavitation has been demonstrated to enhance HIFU heating by increasing the effective ultrasound absorption. 12,13 Therefore, the HIFU heating enhancement at a relatively low HIFU intensity when the PAI system was operating in this study was due to the induced acoustic cavitation in soft tissue. While the application of HIFU therapy is expanding, the concerns related to HIFU treatment include prolonged treatment time for large tumors and skin burns.…”

“…The introduction of cavitation has been investigated as a mechanism to increase the local ultrasound absorption and enhance heating in HIFU. 12,13 Cavitation has been shown to yield elevated heating rates above those produced by classical absorption in tissue 14,15 and can provide a means for improving the efficacy of HIFU treatment. However, preexisting nucleation sites for cavitation are not omnipresent in most tissues in vivo.…”

“…Either ultrasound contrast agents (UCA) [16][17][18] or nanoparticles have been studied as methods of delivering nuclei into the target region. 13 The use of UCA and nanoparticles, however, requires the systematic injection of foreign particles into the blood stream and would cause much concern regarding the toxicity, efficiency, etc. This letter reports a particle-free, photo-enhanced HIFU heating method with the utilization of a diagnostic laser system.…”

Enhancement of heat and mass transfer by cavitation

“…HIFU generates a high intensity focused ultrasonic beams on the target, leading to the significant rise of the local temperature for killing the tumors. For a comprehensive review, readers are referred Coussios and Roy [64]. Figure 15 shows the temperature rise increment versus pressure amplitude of HIFU.…”

Factors Affecting Bacterial Propagation towards Tumor Microenvironments

“…The current state of the art investigates various remote-controlled delivery strategies to overcome poor lo calization of drug carriers to disease sites. Ultrasonic waves and light directed targeting of nanoparticles to disease sites have been recently investigated and show great promise for remote-controlled DDS [11][12][13][14][15]. Despite these promising advances, self-propelling/ autonomous swimmers remain the most encouraging active DDS platforms.…”