Tissue Temperature Effects on Cavitation During Focused Ultrasound Nerve Modulation

Focused ultrasound (FUS) neuromodulation can induce therapeutic effects, such as decreasing perceived pain. To ensure safety during FUS and to better understand the role of cavitation during in vivo neuromodulation, factors influencing cavitation activity must be well understood. Tissue temperature may change between patients and heat may accumulate during therapy. Previous studies have shown a dependence of inertial cavitation thresholds on tissue shear modulus, which changes with temperature. Tissue temperature may therefore affect the intensity of cavitation in the tissue, yet this has not been well-characterized. This study sought to assess the relationship between tissue temperature and levels of cavitation under FUS in vivo. Cavitation was recorded during each sonication and analyzed using calculated passive cavitation images and cavitation doses. Two study designs were used to evaluate cavitation across tissue temperatures of 30-38°C. Our results showed that greater cavitation intensities occurred at higher tissue temperatures. Thus, temperature elevation and cavitation events should be monitored during FUS therapies.