I was also wondering why the sizes change from one scan to another and was told that this is very normal, I was checked with PET scan along with a CT scan and also an MRI and each one the measurements varied. All I was told when I asked why this is happening and they said that each machine takes pictures but they are never the same due to different cameras and how the pictures are taken. I'm not sure if I explained this any better than they did but at the end of the day it's all good and very normal, they will inevitably get the correct information. As cancer patients we want to know every little detail and none of us are what they refer to as ostriches, we truly are facing up to everything that comes our way. This is to say that even though we express our fears hear, we are truly a courageous group of people and even able to lend support to others during our own troubles, I say bravo to all of you.