A prostate-specific membrane antigen positron emission tomography (PSMA PET) scan is an imaging test used to detect prostate cancer throughout the body. It uses a radioactive substance that targets a protein called PSMA, or prostate-specific membrane antigen, which is expressed by prostate cancer. This makes it more accurate for prostate cancer than other types of imaging tests. The exam doesn’t require fasting. And patients are encouraged to drink fluids before and after their exam.