My endo said to me that they can detect whether the I-131 is successful just by taking a blood test..
Full body scan checks for other cancer throughout the body to see if thyroid cancer spread to other parts of the body.
Good questions....the one thing my doctor told me is they look at your chest to see if there is cancer on your lungs since that is the first place it goes. The other part, I do not know. Congrats on the clear scan.