During the scan a thin beam of x-ray is focused on a specific part of your body. The x-ray beam is picked by an electronic detector which records the information and constructs an image on a TV screen. During some CT Scans, a contrast material is used to outline blood vessels or fill in organs of the body (ie: liver, kidney) so that they can be seen more easily.
Most abdominal CT examinations require that you not eat or drink from the midnight prior to your exam. All other CT examinations requiring the administration of contrast material require 2 hours of additional fasting prior to exam. A CT Scan can take from 30-90 minutes.