UCSF

Catheter-based ultrasound technology has demonstrated locally targeted heating for ablation or hyperthermia treatment of cancerous tissue with minimal heating of organs at risk. Site-specific selection of device parameters and treatment strategies is necessary for achieving thermal goals. This dissertation investigates the influences of applicator parameters and treatment strategies on heating patterns in the prostate and cervix using biothermal simulation, which translates into the design of an intrauterine ultrasound applicator that is experimentally characterized and implemented in clinical treatment. Thermal therapy offers potential for prostate cancer/BPH treatment with reduced morbidity. Ultrasound absorption by pelvic bones can cause pain and damage to adjacent nerves. Guidelines for device properties and treatment regimens in relation to prostate size and pelvic bone distance are developed by analyzing their impact on bone heating and treatment time during transurethral prostate ablation. A sectored tubular design is superior to planar and curvilinear designs in reducing bone heating and treatment time with bone <3 cm from the gland. The feasibility of the endocavity ultrasound device, consisting of an array of multi-sectored tubular transducers, to heat tumor targets in the cervix is explored with extensive theoretical analysis. Coverage of 4-5cm targets with therapeutic temperature (>41°C) is possible, using sector orientation for preferential avoidance of rectum and bladder. Hyperthermia delivery in conjunction with interstitial devices is investigated using treatment planning software for 14 patient cases. Temperatures >41°C throughout targets are achieved in most cases using sectoring and aiming to limit Tmax <47°C and rectum and bladder <41.5-42.5°C. Devices were characterized for acoustic emission, imaging compatibility, radiation attenuation, and thermal output using implanted thermometry and MR temperature imaging. Collimated acoustic output with independent power control to sectors and transducers is demonstrated and used to produce tailored heating along the device length and in angle with temperatures of 41°C >2cm in tissue. Thermal delivery is more penetrating than implantable RF devices and more controllable than deep heating technology. The applicator was implemented in two clinical treatments, demonstrating facile integration with HDR brachytherapy, delivery of temperatures >41°C throughout the target, and resulting in disease remission without adverse side effects in one patient.