ABSTRACT Prostate cancer is the leading cancer diagnosis and the second leading cause of death in men, affecting one of every six men in the United States. Radiation therapy or surgery are considered the gold standard of treatment modalities for prostate cancer for organ confined disease with generally excellent outcomes, but can result in incontinence, impotence, rectal bleeding and urethral burning. Procedure costs, complete procedure duration, and therapy delivery duration remain issues. Recent advances in multi-parametric MRI and registered biopsy techniques can identify regions of dominant intraprostatic lesions (DIL) to stage and target tumors. In consideration of an alternative to ionizing radiation or prostatectomy and their associated morbidity, recent clinical studies have demonstrated the potential role of thermal ablative techniques. Although promising, these interventional technologies have limited control of the shape and extent of the ablation zone, require multiple or overlapping insertions, often with unnecessary complications. Image-guided HIFU produces multiple small ablation zones and require repositioning of focus to increase volume, but targeting regions immediately adjacent to the rectum or in the anterior prostate is difficult, MRI guided systems require complex and costly infrastructure, and long treatment durations. Intervening normal tissues, gas, and bone are problematic. There are inherent characteristics of currently applied ablation systems that (i) limit their ability to deliver truly conformal destruction of focal disease while minimizing damage to the rectum or neurovascular bundle (NVB), (ii) require significantly long procedure times, and/or (iii) are complex, at limited number of centers, and require expensive infrastructure. Proposed minimally invasive interstitial needle high-intensity ultrasound applicators with highly conformal and penetrating heating patterns, coupled with 3D tracked ultrasound image guidance, treatment planning, intraprocedure therapy monitoring, can be combined to provide an ideal mechanism for conformable precise thermal surgery in prostate. The objective of this project is development of an image- guided interstitial ultrasound ablation system combined with MP-MRI to US image registration, electromagnetic tracking, and biopsy maps for truly 3D controllable and conformal thermal ablation for treatment of both early stage localized and identified high-risk prostate cancer, which is faster and more practical than existing technologies. Unlike HIFU, our device is placed directly into the target under image guidance to treat disease focally without affecting other tissues, with a much shorter 510(k) FDA clearance path. Our approach and technology will provide sophisticated, highly-integrated 3D conformal therapy which is readily disseminated and is practical for mainstream acute care hospitals and outpatient surgery centers. We propose to develop a short duration treatment, precisely targeted therapy for prostate cancer with less side effects than radiation or surgery. The major goal of the proposed project is to complete an ultrasound image guided ultrasound ablation system to treat prostate cancer and performance validation in FDA GLP study.