Courtesy of Intermountain Medical Imaging, Boise, Idaho.

Figure 1 shows an angiogram (a type of X-ray) of a normal neck artery (carotid artery) with smooth walls. Figure 2 shows a narrowed carotid artery with ulcerated plaque (the surface of the plaque is irregular and broken) that is the source of clots. The clots travel to the brain and cause TIA symptoms.