Mechanical and Civil Engineering Seminar

Histotripsy is an emerging method of noninvasive focused ultrasound surgery that can controllably disintegrate tissue. This effect is accomplished by applying short, high-amplitude pressure pulses to nucleate cavitation bubbles in the tissue that mechanically stress it to the point of failure. Histotripsy has many potential applications, such as dissolving obstructions in the vasculature or ablating tumors. To develop a mechanistic framework for this technology, experiments have sought to characterize cavitation nucleation under relevant ultrasound exposures. Using extremely focused transducers, we have measured the likelihood of inertial cavitation during a single, short ultrasound pulse in tissues, and found that cavitation is consistently produced when the tensile pressure at the focus exceeds ~30 MPa. The probability curves and derived nuclei distribution are similar between several tissues and other water-based media. Observed trends with temperature and ultrasound parameters are accurately described by classical nucleation theory. This characterization may be applied to create a stochastic model of cavitation and tissue ablation for therapy planning and new strategies for focused ultrasound surgery.