I had a mri prior to my surgery that i think told them where and how large the tumor was. I am scheduled for a cat scan with the rad on'gist this friday to map out where he will be rad me. No one has mentioned a pet scan to me. What is the difference between the three different types of scans? I am confused as to the difference between these three different scans. Is one better than another in exposing any remaining cancer? Thanks for your help in advance. Dan