There is general consensus or set standard for scheduled scanning after treatment with a PET/CT, MRI or CT scan, in absence of any suspicion for cancer. NCCN guidlines do recommend post treatment scanning, 3-6 months, but only for T3, T4 disease for oropharynx, larynx cancers, and oral cancer is not mentioned as one. It's basically up to the doctor, and hospital's policy. They do have other set scheduling for physical, visual and palpable examination the first year every 3-6 weeks, then progressively further apart each year, and chest x-ray yearly, TSH testing at least twice a year.

My scanning at several CCC seem to be 3 months post treatment, then 6 months after that. I never made it past that without a recurrence, but it would go to yearly, probably after the first year. Mine were all PET/CT scans, around 14, but one time I needed an MRI to help identify a smaller area that was too scattered on the PET scanning. My ENT wanted to do a CT last time, seems they alternate PET/CT then a CT, but my RO insisted on a PET/CT, which is highly sensitive, and can detect cancer as small as 5mm vs CT and MRI that is usually larger than 1cm. The PET did identify a tumor that was 3mm x 7mm in my cervical neck.

As to which type they use also depends on what thier looking for or at. In genetal CT is good for bone, is the cheaper and most often used. MRI is good soft tissue, blood, and vein lines, PET/CT the whole body. CT and MRI may show false positives after surgery since they may not be able to differentiate between that and a tumor, but the PET/CT works on metabolic activity, but can show false positives too due to being highly sensitive. In general, the least accurate is a CT, then an MRI and PET/CT, but again depends, and sometimes more than one type test may be required. Upon diagnosis I had a CT showing tumor activity, but then was a sceduled for a PET/CTto show the whole body activity, and scope larger than the CT.

I hope this helps.