I've had three CT scans - abdominal, chest & sinus. None showed cancer.
A sinus CT scan is no big deal - less radiation than a mammogram, and it took three doctors pushing for the abdominal CT before I finally agreed. But I seriously regret the chest CT scan. I got it eight years ago to reassure myself. Sure, it reassured me for a year or so, but now it's out of date and I'm stuck with ongoing radiation concerns.
If you have to push for a test, I like MRIs, sonograms and simple, low-dose X-rays. Do not get a CT scan unless your doctor genuinely thinks it's necessary (not just because you've convinced him or her that you might need it).