What is involved in a sinus cat scan and why can't I eat?

With a CAT scan or CT scan. Physicians will inject an intravenous contrast dye that will help to improve the quaility of images that develop. Some of the side-effects of the dye are: nausea and discomfort and in certain cases severe allergic reactions.

It is recommended that patients do not eat before a CT scan to reduce the possible risk of feelings of nausea turning into a bout of vomiting. If you vomit while lying on your back for the scan, you may aspirate some of your stomach contents and possibly develop pneumonia.