An aneurysm (aneurism) is a localized dilatation or swelling of an artery wall. The main risk factors for an aneurysm are arterial hypertension and atherosclerosis.
Aneurysms occur most commonly in cerebral arteries or the abdominal aorta. The swelling can measure up to several centimeters! The danger is that an aneurysm can rupture, which would cause internal bleeding. The internal bleeding would in turn cause complications that can come on very quickly and require emergency treatment.
If the aneurysm is discovered before any rupture, it can be treated in a noninvasive way using "coils" (small platinum springs).
In the case of a brain aneurysm, as illustrated in the animation, the coil is placed using a catheter. The catheter is introduced through the groin area (or the arm) and is guided to the brain. Once the catheter has reached its destination, the coils are deployed.
The use of medical imagery for treatment rather than diagnosis is called interventional radiology.