Browsing by Author "Edsall, Connor William"

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    Ultrasonic Effervescence: Investigations of the Nucleation and Dynamics of Acoustic Cavitation for Histotripsy-Based Therapies
    Edsall, Connor William (Virginia Tech, 2023-01-23)
    Histotripsy is a noninvasive mechanical ablation method that uses focused ultrasound to disintegrate target tissues into acellular homogenate through the generation of acoustic cavitation and is currently being developed for numerous clinical applications. Histotripsy uses high-pressure (>10 MPa), short-duration (<15 cycles) pulses to cause the rapid expansion and collapse of nuclei at the focus resulting in large applied stress and strain in the adjacent tissue. At a sufficiently high pressure above the target medium's intrinsic cavitation threshold and an adequate number of applied pulses, cavitation "bubble clouds" create precise lesions with high fidelity to the region of the focus. Despite advances in histotripsy, additional research is still needed to better understand the acoustic cavitation nucleation process and its effects on therapies using focused ultrasound. This understanding is critical to better predict and control pulse dose for more rapid and efficient ablation procedures, to reduce off-target cavitation events for safer focused ultrasound therapies, and to localize ablation for high-precision procedures near critical structures or treatments without active imaging guidance. In this dissertation, I investigate the nucleation and dynamics of ultrasonically generated acoustic cavitation for novel applications of focused ultrasound. My Ph.D. thesis focuses on (1) investigating the effect of histotripsy pulsing parameters on bubble cloud cavitation nucleation, bubble dynamics, and ablation efficiency, (2) investigating the effect of nuclei characteristics on the threshold for cavitation nucleation and resulting bubble dynamics for therapeutic applications, and (3) developing methods alter select characteristics and dynamics of acoustic cavitation by adjusting pulsing parameters to optimize ablation efficiency in conventional and nanoparticle-mediated histotripsy. The culmination of this thesis will advance our understanding of the nucleation and behavior of acoustic cavitation from pulsed focused ultrasound and develop innovative systems to improve the efficacy, efficiency, and safety of clinical focused ultrasound therapies.