Conformal Heating of the Prostate for the Treatment of Localized Cancer using MRI-guided Transurethral Ultrasound

• Main Author: Burtnyk, Mathieu
• Other Authors: Bronskill, Michael
• Language: en_ca
• Published: 2011
• Subjects: MRI-guided ultrasound therapy; Feedback temperature control; Prostate therapy; 0760; 0541
• Online Access: http://hdl.handle.net/1807/29673

Prostate cancer is the most prevalent cancer and the third-leading cause of cancer-related death among men in the developed world, with the number of cases expected to double within the next 15 years. Conventional therapies offer good control of local disease but are associated with high complication rates reducing long-term health-related quality-of-life significantly. MRI-guided transurethral ultrasound therapy has emerged as an attractive, minimally-invasive alternative for the treatment of localized prostate cancer, where the entire gland is heated to temperatures sufficient to cause irreversible thermal coagulation. A device inserted in the urethra uses multiple ultrasound transducers to produce directional heating patterns directly in the prostate. Adjusting the ultrasound power, frequency and device rotation rate enables high spatial control of the thermal lesion. MRI provides information essential to the accurate targeting of the prostate; anatomical images for device positioning and treatment planning, and quantitative temperature measurements within the prostate to compensate for dynamic tissue changes, using feedback control. This thesis develops a complete treatment delivery strategy for producing conformal regions of thermal coagulation shaped to whole-gland prostate volumes, while limiting the thermal impact to the surrounding important anatomy. First, acoustic and thermal simulations incorporating a novel temperature feedback controller were used to model and shape regions of coagulation to human prostate geometries with a high degree of accuracy. Second, treatment delivery strategies were developed and simulated to reduce thermal injury to the surrounding anatomy, below the threshold for sustained damage. Third, experiments in tissue-mimicking gel phantoms confirmed the predictive accuracy of the simulations and the feasibility of producing conformal volumes of coagulation using transurethral ultrasound devices and MRI-temperature feedback. This work forms the basis of clinical treatment delivery methods and supports the use of the simulations as a planning tool to enhance the inherent compromise between safety and efficacy on a patient-specific basis.