An aneurysm is an abnormal dilatation of a blood vessel. The most severe complication of an aneurysm is rupture of the blood vessel. Ultrasound imaging techniques, CT, and MRI are usually used to diagnose aneurysm.

Aneurysm

http://www.web-books.com/eLibrary/Medicine/Cardiovascular/Aneurysm.htm

Angiogram

As seen in an angiogram