Prostate Cancer, the most prevalent male cancer and second leading cause of male cancer death, is currently detected by screening PSA and physical examination and confirmed with TRUS-guided prostate biopsy. Current diagnostic sensitivity is limited by poor visualization of tumor and inadequate sampling. Our fundamental hypothesis is that sonoelastography imaging can enable the detection of prostate cancer that otherwise appears normal in conventional in-vivo US imaging. A corollary of this hypothesis is that 3D sonoelastography can demarcate and help to calculate the volume of a suspected tumor region. Sonoelastic ultrasound imaging will enable earlier prostate cancer diagnosis due to better biopsy guidance and fewer false negative biopsies. Three-dimensional tumor volume analysis will provide quantification and localization for customized treatment, including tumor boost dose in brachytherapy. We propose a three-stage research plan to develop the technology of sonoelastography to test this hypothesis: Stage 1. Equipment optimization of vibration source, frequency, signal processing, 3D rendering and analysis will be tested in Phantom and ex-vivo tissue models using a GE Logiq 700MR with specially configured software. Stage 2. Optimized parameters will be applied to fresh, whole prostatectomy specimens from patients with prostate cancer, and correlated with step-section pathology. Volumetric and morphologic parameters of sonoelastic images and rendered volumes versus specimen dimensions will also be assessed. Further adjustments will be made to hardware and software as suggested by these results. Stage 3. In-vivo scans will be performed on consenting patients screened for prostate cancer subsequently referred for radical prostatectomy and in selected control patients without prostate cancer undergoing cystoprostatectomy. Comparisons will be made with specimen scans and pathology results as in Stage II. Successful verification of these postulates will permit significant improvement in prostate cancer detection and treatment.