I will add to the pre-PET advice to not chew gum. That was on my hospital's instruction sheet. My son is a radiologist, and he says that, since the PET measures metabolic activity, you don't want to over-exercise your mouth tissues and cause inaccurate results, since our mouths and throats are what we need most to see clearly on the scan. I think that it would also apply to excessive talking.....just do all that you can do to ensure an accurate test, so if being a little quieter and calmer than usual...and not eating or chewing gum...will help, then it is a small price to pay.