PET scans are done by first giving an IV of glucose that has a radioactive marker. Cancer cells have a higher uptake of sugar than regular cells so it tends to concentrate the radiation which is then read by the scanner. It is a long scan and painless. The accuracy is enhanced if combined with CT. If you are healing from radiation and/or surgery there is a possibility of more false positives where healing is taking place. All scan modalities have a certain degree of false positives and are never used as a single diagnostic tool, merely an adjunct to the biopsy, palpation exam, nasolarynoscope, MRI, blood work, tumor markers, CT and mirrors.

PET/CT's have shown reading up to 98% accuracy. PET alone is a little lower.

Most of us have had PET scans for the original workup. Some have regular PET scans as part of their follow-up protocol.