Hi Heather...as far as i know these are routine tests so the Drs can have a 'baseline' picture of everything..then they can refer to them later when these scans are schedules again..
my oncologist likes to do a bone scan about every 12 mths, i have a chest/abdo CT scan every 3 mths. In my case i had chest pain 2 weeks after my mastectomy surgery and they did a CT to check for clots, but found tumours in my lungs which were not on the pre-surgery scan...so for me at least we knew that these were very young tumours and we were onto them really quickly-all going well so far and feeling great..
Hope this puts ur mind at ease at least a little..
Sam :)