ND means "Neck Disection.

PET/CT's are reportedly 98% accurate. Recent healing can give false readings as others have mentioned. Since the scan has the advantage (over a plain PET) to locate regions of interest with great accuracy, because of the CT aspect, I would think that the doctors would ignore the areas where healing is happening and simply look for metastasis elsewhere. The NCCN Oncology Practice Guidelines do not recommend post Tx PET or PET/CT scans, although some institutions routinely order them. My CCC recommended an annual MRI.

Early scans of any type, particularly post Tx, will show all kinds of regions of interest so don't freak out (if you get the raw scan report) before its interpreted by your team.

When I was being set up for radiation, I got all 3, pre Tx, PET, CT and MRI. They needed them to plan the radiation treatment protocol.

My PET scan was a full body scan.

3 months, post surgery, is not that close. Some here have have PET scans 3 weeks post surgery. He still may get false positives at the surgical site, as the uptake in sugar (and radioisotope) is very similar to the uptake from a tumor.

If it were me I want want to know the "risks and benefits" of the scan and why the RO is ordering it, before simply refusing it. Tongue cancer tends to be more aggressive so extra vigilance is in order.