The only way to directly look at the coronary arteries was via a cardiac catheterization and coronary
angiogram This procedure uses intravenous dye which contains iodine and CT scanning to image the
coronary arteries. While the use of catheters is not necessary (thus the term “noninvasive” test applies to
this procedure), there are still some risks involved. In people allergic to iodine, pretreatment with
medications is necessary to prevent allergic reactions to the dye.