After a prostate is removed for cancer, the PSA should remain undetectable (<0.1). If the PSA starts to rise, traditional imaging often takes years to determine the location of the recurrence. New imaging techniques such as PET scans have shown an improved ability to detect these recurrences. Currently the 2 most popular types of PET for prostate cancer are C11-Choline or PSMA PET scans. A recent study indicates that between these 2, PSMA is better early on when the PSA remains below 1.5, while the results are similar above PSA of 1.5. A current limitation of these studies is the lack of availability in the community.
https://pubmed.ncbi.nlm.nih.gov/32068488/