Histotripsy: Non-invasive ultrasound surgery.

Histotripsy is a method of ultrasonic surgical intervention using tissue disrupting effects of cavitating microbubbles in an intense sound field. Targets for this form of therapy include removal of malignant and benign growths in many parts of the body. While thermal methods of ultrasound tissue ablation have been in development for more than 50 years, recent availability of reliable, extremely high power transducers has made histotripsy methods practical. The dissertation work presented here is in three chapters. Chapter 2 presents designs of transducers and electronic systems specific for histotripsy. Included are some of the most powerful therapeutic ultrasound systems in the world and the first 512 channel phased-array therapy system. Chapter 3 presents experiments to analyze in detail the histotripsy process and construct models for ablation. Proper control of cavitation using low duty cycles to avoid bulk tissue heating is shown to produce very precise tissue ablation with sharp treatment margins. Avoidance of heating is shown to be aided by using an electronic scanning phased-array transducer system. Chapter 4 presents work on various non-invasive imaging feedback methods to verify targeting, monitor histotripsy treatment, and to assess treatment outcome. Ultrasound imaging is demonstrated for in-vivo and ex-vivo ablation guidance permitting real-time monitoring of treatment. Ultrasound imaging and magnetic resonance imaging are demonstrated to produce useful contrast between disrupted and surrounding tissue allowing non-invasive assessment of treatment effects. Results suggest that with additional optimization of treatment methods, clinical trials for histotripsy surgery should be possible. Chapter 5 presents some initial clinical targets for histotripsy with along with specific considerations for each.PhDApplied SciencesBiomedical engineeringHealth and Environmental SciencesMedicineUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126705/2/3276173.pd