MRI (magnetic resonance imaging) uses a large magnetic field to produce an image of the brain. Like the CT scan, it shows the location and extent of brain injury. The image produced by MRI is sharper and more detailed than a CT scan so it's often used to diagnose small, deep injuries.
Several blood flow tests exist; most use ultrasound technology. A probe is placed over the suspect artery — especially arteries in the neck (carotid) or at the base of the skull (vertebral) — and the amount of blood flow through a blood vessel is determined.
Examples of blood flow tests are B-mode imaging, Doppler testing and duplex scanning. These tests give detailed information about the condition of arteries.
Another blood flow test is a medical procedure called angiography (arteriography or arteriogram). This test is like a cardiac catheterization, only the catheter is placed in the arteries of the brain rather than in the arteries of the heart. In this test, a special dye is injected into the blood vessels and an X-ray is taken.
Angiography gives a picture of the blood flow through the vessels. This allows the size and location of blockages to be evaluated. This test can be especially valuable in diagnosing aneurysms and malformed blood vessels and providing information before surgery.