CT scan can be done with or without contrast. Contrast is used to lighten up the vascular structure. Sometimes they will test your renal function prior to contrast, patient who has impaired renal function don't really tolerate contrast. If you are a healthy 20 year old, it should be fine. Some say it taste like pineapple juice....

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Added on February 14, 2011, 6:24 pmyup and CT scan is definitely more hazardous in terms of radiation. However, it does provide very good anatomical details

This post has been edited by d(@@)b: Feb 14 2011, 06:24 PM