In most cases, Medicare does cover PET scans, as long as they are considered medically necessary.
A Medicare Supplement Insurance (Medigap) plan can help pay for your out-of-pocket Medicare costs when you get a PET scan, such as deductibles and copays.

Understanding PET Scans
PET scans help detect cancer and other diseases, including those in the heart and brain.
Positron emission tomography scans (PET scans) allow doctors to check for a number of diseases in your body.
These include:
With PET scans, patients are given a special dye, injected in their veins. Bodily organs absorb this dye. Then, when highlighted under a PET scan, these images reveal characteristics such as blood flow and oxygen use.
These important measures help physicians diagnose illnesses by providing a clear window into complex diseases, including:
Coronary artery disease
Memory disorders
Brain tumors
Additionally, PET scans help your physician judge whether you have a cancer that has spread through your body and can even reveal how chemotherapy is affecting a tumor.