Can at pt and ct scan be used to diagnose cancer?

I am: Not sure what you mean by noncancer. However, a pet scan is a targeted exam used to either diagnose or follow human disease, usually cancer. Some cancers will not be seen because they don't accumulate sufficient glucose or are very small. There are multiple other causes of increased uptake of glucose that are noncancerous in origen.

Sometimes....: The ct that is done with a pet is primarily to improve the pet image by correcting the data the pet camera receives from the patient's body for differences in density (bones denser than muscles, then fat, then air (lung) density). Some scanners have better ct images. So, sometimes the ct makes an incidental diagnosis. However, the ct is not the same as a diagnostic ct with IV and oral contrast.