A cardiac PET scan involves the use of a radioactive tracer to create detailed images of the heart’s function and blood flow. The radiation dose from a cardiac PET scan primarily comes from the radiotracer injected into the patient, which emits positrons detected by the PET scanner to form images.
The amount of radiation contained in a cardiac PET scan varies depending on the specific radiotracer used and the protocol (rest and/or stress imaging). Typically, the administered activity for cardiac PET myocardial perfusion imaging ranges from about 93 to 352 megabecquerels (MBq), depending on whether the scan is done in one day or two days and whether stress is induced pharmacologically or by exercise. For example, a common dosing scheme might be around 93 to 111 MBq for rest imaging and 222 to 352 MBq for stress imaging in a one-day protocol.
In terms of absorbed radiation dose to the heart wall, values reported are approximately 5.3 milligray (mGy) for rest imaging and can rise to around 22 mGy or more for stress imaging, depending on the dose administered. The total radiation exposure to the patient from a cardiac PET scan is generally considered low compared to other imaging modalities like CT scans or conventional nuclear stress tests.
To put this in perspective, the effective radiation dose from a typical cardiac PET scan is often in the range of 2 to 5 millisieverts (mSv), which is roughly equivalent to the natural background radiation a person receives over about one to two years. This low dose is partly due to the short half-life of the commonly used PET tracer fluorodeoxyglucose (FDG) or other cardiac-specific tracers, which decay rapidly (with half-lives around 110 minutes), minimizing radiation exposure after the scan.
Patients undergoing cardiac PET scans are advised to avoid close contact with radiation-sensitive individuals such as infants, children, and pregnant women for a short period after the scan, typically around 12 hours, to allow the radioactivity to decay to safe levels.
Overall, cardiac PET scans provide a valuable diagnostic tool with a relatively low radiation burden, balancing the need for detailed cardiac imaging with patient safety considerations. The radiation dose is carefully controlled by adjusting the injected activity and using advanced PET/CT technology to minimize exposure while maintaining high-quality images.
