Debbie,
this depends on your docs order but they generally do full body scan. After all you are already there and are already injected with the tracer. The idea is to look for distant metastasis (hopefully not present). The CT portion may also be done with a contrast agent, which may give you a warm rush. (no big deal). This may take anywhere from 20-40 minutes, depending amongst other things on how new (sensitive) the equipment is. To my sense it is quite roomy in the scanner and the tube is rather short (probably depending on the model)... but you do have to keep still. Remember to follow the preparations for the scan.

Markus