Magnetic resonance angiography
DefinitionMagnetic resonance angiography is an MRI exam of the blood vessels. Unlike traditional angiography that involves placing a tube (catheter) into the body, MRA is noninvasive.
Alternative NamesMRA; Angiography - magnetic resonance
How the test is performedYou may be asked to wear a hospital gown or clothing without metal fasteners (such as sweatpants and a t-shirt). Certain types of metal can cause blurry images.You will lie on a narrow table, which slides into a large tunnel-shaped scanner.Some exams require a special dye (contrast). The dye is usually given before the test through a vein (IV) in your hand or forearm. The dye helps the radiologist see certain areas more clearly.During the MRI, the person who operates the machine will watch you from another room. The test may take 1 hour or more.
How to prepare for the testYou may be asked not to eat or drink anything for 4 - 6 hours before the scan.Tell your doctor if you are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious, or your doctor may suggest an "open" MRI, in which the machine is not as close to the body.Before the test, tell your health care provider if you have:Brain aneurysm clipsArtificial heart valveHeart defibrillator or pacemakerInner ear (cochlear) implantsInsulin or chemotherapy portIntrauterine device (IUD)Kidney disease or dialysis (you may not be able to receive contrast)NeurostimulatorRecently placed artificial jointsVascular stentWorked with sheet metal in the past (you may need tests to check for metal pieces in your eyes)Because the MRI contains strong magnets, metal objects are not allowed into the room with the MRI scanner:Pens, pocketknives, and eyeglasses may fly across the room.Items such as jewelry, watches, credit cards, and hearing aids can be damaged.Pins, hairpins, metal zippers, and similar metallic items can distort the images.Removable dental work should be taken out just before the scan.
How the test will feelAn MRA exam causes no pain. If you have difficulty lying still or are very nervous, you may be given a medicine to relax you. Too much movement can blur images and cause errors.The table may be hard or cold, but you can request a blanket or pillow. The machine produces loud thumping and humming noises when turned on. You can wear ear plugs to help reduce the noise.An intercom in the room allows you to speak to someone at any time. Some scanners have televisions and special headphones that you can use to help the time pass.There is no recovery time, unless you were given a medicine to relax.
Why the test is performedMRA is used to look at the blood vessels in all parts of the body, including the head, heart, abdomen, lungs, kidneys, and legs.It may be used to diagnose or evaluate conditions such as:Arterial aneurysmAortic coarctationAortic dissectionStrokeCarotid artery diseaseAtherosclerosis of the arms or legsHeart disease, including congenital heart diseaseMesenteric artery ischemiaRenal artery stenosis (narrowing of the blood vessels in the kidneys)
Normal ValuesA normal result means the blood vessels do not show any signs of narrowing or blockage.
What abnormal results meanAn abnormal exam suggests a problem with one or more blood vessels. This may suggest atherosclerosis, trauma, a congenital disease, or other vascular condition.
What the risks areMR angiography is generally safe. It uses no radiation. To date, no side effects from the magnetic fields and radio waves have been reported.The most common type of contrast (dye) used contains gadolinium. It is very safe. Allergic reactions to the substance rarely occur. However, gadolinium can be harmful to patients with kidney problems who require dialysis. If you have kidney problems, please tell your health care provider before the test.The strong magnetic fields created during an MRI can cause heart pacemakers and other implants to not work as well. It can also cause a piece of metal inside your body to move or shift.
ReferencesPennell D. Cardiovascular magnetic resonance imaging. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. St. Louis, Mo: WB Saunders; 2007:chap 17.Jackson J, Allison DJ, Meaney J. Angiography: principles, techniques, and complications. In: Grainger RC, Allison D, Adam A, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 6.