I am scheduled to have this done in the morning. I am starting to get worried because I have been reading about serious side effects from the contrast like allergic reactions. Also, the radiation exposure..one cat scan equals like 750 xrays and I have to have it of my head and neck. I have had a cat scan of my head several years back and one of my heart a few years ago. I am really worried about the radiation, but I also feel that I need this test because they need to look at the blood vessels of my head and neck to make sure I am not having some type of tias..any input would be greatly appreciated!!