Colleen,
you have it backwards. The PET/CT is very accurate because it is a PET combined with a CT scan and shows very clear anatomical reference points and bone structures. The PET by itself is less accurate. Many times PET scans are given only once in the diagnostic work up as a triage technique to determine if the cancer has spread. Although a few here have regular PET scans, many do not. It is not part of the NCCN Oncology Practice guidelines for regular followup so I suspect that many insurance companies won't pay for them. In early post Tx they are also prone to false positives because of the glucous uptake of the scar tissue. It is also the most expensive scan, the radioisotope, injected by IV, has to be manufactured on a cyclotron and delivered within hours of use by courier. It is also a very long scan taking about an hour to complete.