I've had a it several times. It's not big deal, just an ultrasound of your arteries. A common by-product of their exposure to radiation is the formation of scar tissue n them, reducing blood flow to the brain. This scar tissue can become a problem, but not like occlusion of the carotids by plaques (from a life of eating to many fats and having high blood lipids) that can break off and cause a stroke. It is a permanent thickening of the wall, and isn't going to get better - nor have a small portion break off causing strokes. But it in some cases it causes the need for a shunt to have to be placed in them to open the area up. I am about 50% occluded, enough where I can get dizzy getting up too quickly or pulling too many G's in my airplane. It started getting worse ironically about year 7. I don't care for the data on coated inserts, nor uncoated ones, so I am living with things the way they are.