A PET scan for prostate cancer, specifically a PSMA PET scan, involves injecting a small amount of radioactive tracer that binds to prostate cancer cells, allowing the scan to detect cancer locations in the body. The radiation dose from this PET scan typically ranges around 5 to 7 millisieverts (mSv). When combined with a CT scan, which is often done simultaneously to provide detailed anatomical images, the total radiation exposure can increase to about 20 to 25 mSv, depending on the CT protocol used.
To understand this better, a PET scan uses a radioactive substance called a radiotracer. In prostate cancer imaging, the tracer targets a protein called PSMA (prostate-specific membrane antigen), which is found in high amounts on prostate cancer cells. After injection, the tracer circulates and attaches to these cells. The PET scanner detects the radiation emitted as the tracer decays, creating images that highlight cancerous areas. The radioactive material used has a half-life, meaning it loses half of its radioactivity over a certain period, which influences how long it remains active in the body.
The radiation dose from the PET component alone is relatively low, roughly equivalent to a few years of natural background radiation exposure. The CT scan adds more radiation because it uses X-rays to capture detailed images of the body’s structure. Together, the PET/CT scan provides both functional information (where cancer cells are active) and anatomical detail (where exactly in the body the cancer is located).
Radiation exposure from these scans is carefully controlled and considered safe for most patients, especially when the diagnostic benefits outweigh the risks. The amount of radiation is higher than a standard X-ray but lower than many therapeutic radiation doses used in cancer treatment. Doctors recommend these scans when precise imaging is needed to guide treatment decisions, such as detecting cancer spread or recurrence.
In summary, a PSMA PET scan for prostate cancer involves a radiation dose of about 5 to 7 mSv from the PET tracer, with an additional 15 to 20 mSv from the CT scan if performed together, totaling around 20 to 25 mSv. This level of radiation is managed carefully to maximize diagnostic benefit while minimizing risk.
