Pilot Study to Investigate Magnetic Resonance (MR) Image Guided Focal Therapy in Prostate Cancer

Background: The ability to treat early prostate cancer is still limited. Thermal ablation methods are being tested for focal prostate cancer therapy. Researchers want to improve on these methods. Objective: To understand if Transurethral UltraSound Ablation (TULSA) in combination with MRI guidance is useful to treat localized prostate cancer. Eligibility: English-speaking adults ages 18 and older with localized prostate cancer that can be seen on MRI and can be treated by thermal ablation. Design: Participants will be screened with the following: * Medical history * Physical exam * Digital rectal exam * Blood and urine tests * Electrocardiogram * Tumor biopsy * Questionnaire to assess urinary tract symptoms * MRI of the pelvis. The MRI scanner is a long, narrow tube. Participants will lie on a bed that moves in and out of the scanner. Participants may also be screened with the following: * Echocardiogram * Chest x-ray * Bone scan * Urodynamic studies to see how well the bladder, sphincters, and urethra hold and release urine * MRI of the brain * Transrectal ultrasound * Computer tomography (CT) scan of the chest, abdomen, and pelvis. A CT scan is a series of x-ray images taken of parts of the body. Some screening tests will be repeated during the study. Participants will have the TULSA procedure. They will have an MRI for guidance. A small ultrasound applicator will be placed into their urethra. It uses heat to destroy the cancer areas in the prostate. It is controlled by a robotic arm. A cooling catheter will be placed into their rectum. Participants will use a urethral catheter for 1-7 days. Participants will have follow-up visits at 3, 6, 12, 18, 24, and 36 months.