I am curious about a few things

alapah said:

are you sure you had a PET scan?
RAI is followed by a scan that is usually referred to as a WBS (Whole Body Scan). The WBS does not expose you to radiation, rather, it picks up radioactive iodine emitted from your body which indicates areas of uptake of RAI. The times I had a WBS the machine was a flat plate type of thing that hovered over my body as it scanned in sections. This type of scan is quite different from a PET scan which is rarely used on thyroid cancer patients (though I have had two because I have an advanced case of the disease and they were looking for metastases).

A PET Scan does expose you to radiation and the process takes a lot longer than a WBS. For a PET scan, patients first receive an IV injection of a radioactive glucose solution and then must sit still for about 45 minutes prior to laying in the machine. In both of my PET scans, the machine was like a CT scanner - the donut type.

My hunch is that you had a WBS, not a PET. That would be standard. BTW, if the WBS shows uptake after a large dose of RAI this is generally a good thing because the indication is that the remaining thyroid cells have absorbed the RAI and likely will be killed by it. For a small dose as follow up, a positive uptake can help the docs determine if you need another large dose. It's not uncommon for patients to get more than one large dose of RAI so don't be alarmed if that comes up - I hope it's all good though and that you don't need more. Be sure to write down your questions for the doctor so you can get answers and peace of mind.
Best to you!
e

alapah said:

ah, ok
That # must be your thyroglobulin level. They do like to see that at zero as it would indicate the absence of thyroid cells which produce thyroglobulin (Tg). But you did have RAI recently? Was that a 'large' dose, like 100 mci or was it a small dose to see if there was uptake? I seem to recall being told that after an ablation dose of RAI the Tg can sometimes rise before falling but this occurs within a certain timeframe (which I cannot remember exactly).

If you were sent for a PET then I assume they did a WBS following your RAI and found no uptake but your Tg # indicates thyroid cells are present somewhere. In that case, they do sometimes order a PET to see if they can locate the source of the Tg. It is possible it's in lymph nodes which don't typically take in RAI for some reason. Usually those are dealt with through surgery or alcohol ablation, rather than RAI.

Do you know what your past Tg readings have been? Are they steady, rising or falling? The trend is important, sometimes more so than the actual number itself. Also, if you happen to have Tg antibodies, the Tg number can be harder to use as a marker. Tg measures thyroid cell activity and not necessarily cancerous thyroid cells, just thyroid cells.

The waiting is definitely rough. Hope you can hang in there!
e