In some institutions registered nurses in radiology are responsible for assessing patients who will receive oral or IV contrast for a CT exam. They will review your allergies and medications and make sure your kidneys are functions properly since IV contrast is eliminated from your body through your kidneys. They may be the ones to place your IV and inject the contrast. Normally the IV contrast used for a CT scan is injected very rapidly. A power injector is used for adult patients.
Nurses may also give rectal contrast or fill your bladder with a diluted contrast solution for specialized exams that image your bladder.