I had a PSMA PET scan done over a year ago with a PSA of 0.7 3 months after surgery. It showed several lesions, but none were in pelvic floor, all were higher in lymph nodes. None of these were seen in a regular PET or CAT scan. Based on the information I received from the scan lab, and the treatment center, 0.2 seems to be where these start to show up. There is some information if you google "Detection level and pattern of positive lesions using PSMA PET/CT for staging prior to radiation therapy"