Patients who meet eligibility criteria and are enrolled will undergo whole-body imaging with 18F-choline PET/CT at 3 time points during the course of treatment that is indicated for castrate resistant prostate cancer. The 1st PET/CT scan is performed at baseline before treatment initiation. The 2nd and 3rd scans are performed at two other treatment-releated timepoints or at approximately 1 month and 3 months after treatment initiation. Change in lesion 18F-choline uptake from baseline measured at each time point will be determined. Cancer 18F-choline uptake will be evaluated as a marker of therapeutic response in comparison to PSA response and symptom scores. Treatment-related changes in tumor 18F-choline uptake occur will be studied after the second and third PET scans to determine the acuity by which changes in tumor 18F-choline uptake can be expected following specific treatments for castrate-resistant prostate cancer. The study evaluates a diagnostic intervention and the treatments themselves are not considered part of the investigation. All treatment decisions will be made independent of the study and must be deemed clinically-warranted by a treating physician.