My mom had a PET scan done back last October. I can tell you some about it. They inject you or you drink this fluid similar to an MRI (I don't know if it's similar in taste or not). The fluid then attaches to the glucoses in your body. Those glucoses then attach to areas and those areas will show up on the PET scan. This is a much newer scan but they are now concluding that it is becoming more and more accurate as they use it. It was first used for cancer diagnosis for colon cancers, lung cancers, etc. but was not very accurate. They are now determining that these can be more accurate than a spiral scan because it does attach to places and that is what shows up on the scan.
Can I be nosey and ask why she is having the scan??? If you have posted about this I'm sorry if I have missed it. It is not painful at all but like an MRI I believe she has to lay very still. The whole thing lasted a few hours and that included letting the liquid get through the body. I was not with her when she had this done, my brother was.
Please feel free to PM me if you need any more info.