I thought I would add a little here to voice a perspective that few will agree with 100%. I don't believe that any technology like PET, which is designed to look for things that have high metabolic activity at a cellular level is a valuable tool by itself. (High metabolic activity means many things most of which are not cancer, and the resulting false positives are a fact of life.) We also know that PET's are really good at showing the bodies high metabolic rate when it comes to healing an area after radiation, surgery etc. which panics plenty of inexperienced doctors, and too many patients. I also don't believe that CT or MRI's are the gift of accuracy, since they can't see things as rule less than 2 mm, or if the slice/view view misses that area they are in, (some take views at 5mm) they will miss it. I also don't believe that any doctor's fingers palpating my neck or his trained eyes looking in my mouth are any guarantee that he will see something that is wrong or feel something out of whack