MRA—a type of magnetic resonance imaging (MRI) study that is obtained with the same scanning machine—uses a strong magnetic field combined with radiofrequency waves to create highly detailed images of blood vessels in the body. (MRA is most often used to examine vessels in the brain, neck, kidneys, and legs.)
The resulting scans, which provide information about blood flow and the condition of blood vessel walls, may then be saved on a computer or on film and examined for abnormalities. To provide better definition of blood vessels on the images, a weakly magnetic contrast dye, such as gadolinium, is sometimes injected into a vein in the arm.
Purpose of the Magnetic Resonance Angiography
- To evaluate people with symptoms of a stroke
- To diagnose lesions that significantly disrupt blood flow in the carotid and vertebral arteries leading to the brain, such as blockages or dissection (leakage of blood between layers of the blood vessel wall)
- To detect and evaluate blood vessel abnormalities within the brain, including aneurysm (abnormal outpouching that is prone to rupture), dilation, inflammation, and arteriovenous malformation (a congenital blood vessel defect)
- To detect and evaluate blood vessel abnormalities in the legs, kidneys and other parts of the body
- To define the blood supply to malignant (cancerous) vascular tumors in the brain
- To detect narrowing of the aorta or aortic coarctation
Who Performs It
- A radiologist or a qualified technician
- MRA is expensive and is often unavailable outside of large cities and major medical centers.
- People who experience claustrophobia may find it difficult to undergo this test, which takes place in a narrow, tunnel-like structure.
- This test may not be possible for severely overweight individuals (over 300 lbs).
- Because the MRI generates a strong magnetic field, it cannot be performed on people who have certain internally placed metallic devices, including pacemakers, inner ear implants, or intracranial aneurysm clips.
- The test should not be done in pregnant women because the long-term effects of MRI on the fetus are unknown.
Before the Magnetic Resonance Angiography
- Do not drink or eat 4 to 6 hours prior to the test.
- Tell your doctor if you suffer from claustrophobia. He or she may administer a sedative to help you tolerate the procedure.
- Tell your doctor if you are pregnant or suspect that you may be pregnant.
- Empty your bladder before the test.
- Tell your doctor if you are allergic to contrast medium (x-ray dye) or any medications.
- Remove any metallic objects, including watches, hair clips, belts, credit cards, jewelry, hearing aids and anything else that contains metal. You may be asked to disrobe and put on a hospital gown.
What You Experience
- You will lie down on a narrow padded bed that slides into a large, enclosed cylinder containing the MRI magnets. You must remain still throughout the procedure because any motion can distort the scan.
- If a contrast dye is to be used, it is injected intravenously, and imaging begins shortly after the injection.
- There is a microphone inside the imaging machine, and you may talk to the technician performing the scan at any time during the test.
- You will hear loud thumping sounds as the scanning is performed. To block out the noise, you can request earplugs or listen to music on earphones.
- The entire procedure takes 10 to 20 minutes, or twice that long if contrast dye is used.
Risks and Complications
- MRA does not involve exposure to ionizing radiation and is not associated with any risks or complications.
After the Magnetic Resonance Angiography
- Sedated patients may be monitored for a short period until the effects of the sedative have worn off.
- You may leave the testing facility and resume your normal activities.
- Blood may collect and clot under the skin (hematoma) at the injection site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
- Inform your doctor immediately if allergic or abnormal symptoms occur.
- A radiologist will examine the MRA images for evidence of any abnormality.
- If a definitive diagnosis can be made, appropriate treatment will be initiated, depending on the specific problem.
- In some cases, additional tests, such as a CT scan or a PET scan of the brain, may be needed to establish a diagnosis and determine the extent of the problem.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media