Magnetic Resonance Angiography

Magnetic resonance angiography (MRA) is a noninvasive, radiation-free test that uses radio waves and a magnetic field to show tissues and structures inside the body, such as blood vessels and blood flow.

MRA equipment consists of a table that slides in and out of a large cylinder-shaped machine. The machine is attached to a computer that processes the radio waves and magnetic fields to create two-dimensional (2D) or three-dimensional (3D) images. Contrast agents, such as gadolinium, are often used with MRA to improve the quality of the images. Contrast agents help make sure that blood flow is detected by the magnetic field regardless of flow pattern.

MRA can help physicians diagnose the following conditions:

Stroke;
Brain aneurysm;
Arteriovenous malformations; and
Blockage in carotid arteries.

PRE-TEST GUIDELINES

Typically, there is no preparation. Occasionally, some patients are asked to fast for 4 to 6 hours before the test.

Patients who may be unsuited for MRA include those who:

Weigh more than 300 pounds;
Have a pacemaker or other metallic devices or implants;
Have worked in an environment where metal shavings may have gotten into the eyes;
Take transdermal medication;
Require continuous life-support;
Suspects or knows she is pregnant;
Have claustrophobia; or
Are extremely anxious, confused, or agitated.

WHAT TO EXPECT

An MRA lasts between 30 to 90 minutes.

The patient changes into a hospital gown and removes any jewelry or wristwatch, then lies on the MRA table. If a contrast agent will be used, it will be injected into a vein in the patient's hand or forearm. Because MRA images can become blurred with motion, the technician may offer the patient a sedative.

During the test, the MRA table automatically slides through a hollow, donut-shaped chamber that exposes the patient to a magnetic field and pulses of radio waves. Throughout the procedure, the scanner produces humming and thumping sounds. The only discomfort from MRA may be from lying still on the hard table.

POST-TEST GUIDELINES

If patients receive a sedative for the MRA, they will need to arrange a ride home. Otherwise, patients can resume normal activities immediately.

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