The Style and Assessment of Transurethral Ultrasound Applicators for Precise MR-guided Prostate Ablation

Thermal ablation of benign prostatic hyperplasia (BPH) and prostate cancer is a minimally-invasive alternative to standard surgical prostate treatments. Minimally intrusive, numerous of the current prostate thermal ablation technologies lack the ability to specifically treat large prostate regions while preventing delicate surrounding structures. This Ph.D. dissertation describes the advancement and evaluation of directional transurethral ultrasound applicators capable of exact image-guided prostate ablation. MR compatible, transurethral ultrasound applicators were created and fabricated using either planar, sectored tubular, or somewhat focused curvilinear transducers. The applicator creates included a linear variety of separately powered transducers incorporated onto a custom multi-lumen catheter, which could be rotated within an inflatable urethral cooling balloon. A computer-controlled, MR suitable motor system was established to turn the applicators during thermal procedures. Controlled image-guided ablation of prostate tissue was demonstrated in numerous in vivo canine experiments. An open bore interventional MR system permitted direct gain access to throughout the thermal procedures with concurrent MR temperature level imaging. Single stationary sonications of the directive transurethral applicators ablated selective prostate regions (20-70 °) out to prostate capsule. Bigger ablation zones were then created by turning the directive applicators in discrete angular actions. The depth of ablation at each angle was managed by continuously controling the applied power level and sonication duration with MR temperature level feedback as assistance. An acoustic and biothermal model of transurethral ultrasound thermal treatments was also developed and verified in this work. Research studies with the biothermal design demonstrated that all three applicator types might conformably ablate prostate tissue out to the prostate capsule border while avoiding thermal damage to rectal tissues. The curvilinear applicator showed the most selective applicator and the tubular applicator required the shortest treatment times and was the simplest to control. In summary, this work represents a major advance in image-guided prostate thermal treatment. There is proven potential for instruction transurethral ultrasound applicators and the technologies developed herein can be easily modified to treat other intraluminal locations such as esophageal and rectal pathologies. With included development and confirmation, the biothermal design may offer a base for future thermal treatment planning systems.

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