What is magnetic resonance angiography?
MRI (magnetic resonance imaging) uses magnetic fields and radio waves to produce two-dimensional or three-dimensional images of the structures inside your body, such as your heart, brain or blood vessels. When this scanning method is applied to the blood vessels, it is also sometimes referred to as MRA (magnetic resonance angiography). MRA helps your physician diagnose the following conditions:
- Bulges in your aorta, called aneurysms
- Tears in your aorta, called dissections
- Problems with your heart that you may be born with, called congenital heart disorders
- Narrowing of the arteries in and around your kidneys, called renal artery stenosis
- Inflammation in your blood vessels, called vasculitis
- Hardening of the arteries (called atherosclerosis) involving the legs or arms
- Blockages in the major arteries that supply blood to your brain, called carotid artery disease
The MRA equipment consists of a table that slides in and out of a donut-shaped machine. A computer attached to the machine processes radio waves and magnetic fields to create two-dimensional or three-dimensional images.
MRA not only helps your physician diagnose your condition, it also helps him or her plan treatment. MRA also may, in some circumstances, have advantages that other tests do not. For instance, MRA does not require X-ray exposure to detect narrowing of arteries, unlike computed tomography (CT) scans or angiograms.
How do I prepare?
Your physician may ask you not to eat 4 to 6 hours before the test, but usually no other preparation is necessary.
You may not be eligible for an MRA if you:
- Weigh more than 300 pounds
- Have a pacemaker or other metallic devices inside your body, such as joints, pins, clips, or valves
- Are on continuous life support devices, such as oxygen
- Are pregnant
- Are claustrophobic
- Are extremely anxious, confused, or agitated and unable to lie still
If you are claustrophobic, your physician may recommend an open MRA. This method may not be useful for all situations, however.
What happens during an MRA?
Your physician will direct you to a special lab or room where a technician will perform the test. The technician will instruct you to change into a hospital gown and remove any jewelry or metallic objects that may be affected by the magnetic field. The technician may give you a sedative to make sure that you lie still during the procedure because motion can result in poor quality images.
The technician will ask you to lie on the MRA table. The table slides slowly through a hollow, donut-shaped chamber that exposes you to magnetic fields and pulses of radio waves. These magnetic fields and radio waves are harmless and painless. The only discomfort that you may feel during the scan will be from lying still on the hard table in an enclosed area.
During the test, the technician may speak to you through a speaker that is inside the MRA room.
Sometimes the technician may inject a contrast dye into your hand or forearm to improve the quality of the images.
An MRA lasts between 30 and 90 minutes.
What can I expect after an MRA?
Usually you can expect to resume your pre-test activity, unless you required sedation during the examination. Your physician will instruct you to arrange for a ride home if you receive a sedative.
Are there any complications?
Complications from an MRA, such as a reaction to the contrast dye, are very unusual.
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Reviwed February 2011