Effect of high intensity focused ultrasound on neural compound action potential : an in vitro study

Therapeutic ultrasound is a promising field with many novel applications in medicine and biology. High intensity focused ultrasound (HIFU) provides the ability to localize the deposition of acoustic energy within the body by thermal effect. In this work a brief description of how the HIFU system works and how it can be used to produce localized thermal lesions on the pathogenic tissues in the human body will be presented. Results of acoustic characterization of a hand-held HIFU system developed in our lab will also be presented. The capabilities of creating controlled reversible and irreversible changes in the compound action potential (CAP) values of a specific neural tissue, i.e. lobster abdominal nerves by adjusting different ultrasound parameters (intensity, exposure duration, etc.) in the HIFU system will also be described. Lobster abdominal nerves were exposed to a 10s HIFU exposure. The focal intensity values for this study were chosen as 100, 175, 275, 400, 525 and 700 W .cm ⁻². It was shown that a trend of small changes in the measured CAP values (increase in the CAP amplitude) could be achieved in the five intermediate intensities, while a drastic decrease in the measured CAP values and total degeneration of the nerve could be observed with the highest focal intensity of 700 W .cm⁻².