Magnetic resonance imaging - lumbar spine; MRI - lower back
How the test is performed
You will wear a hospital gown or clothes without metal snaps or zippers (such as sweatpants and a t-shirt). Some types of metal can cause blurry images.
You will lie on a narrow table that slides into a large tunnel-like tube.
Some exams require a special dye (contrast). Most of the time, you will get the dye through a vein (IV) in your hand or arm before the test. You can also get the dye through an injection. 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 most often lasts 30-60 minutes, but may take longer.
How to prepare for the test
You 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. 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 clips
Certain types of artificial heart valves
Heart defibrillator or pacemaker
Inner ear (cochlear) implants
Kidney disease or dialysis (you may not be able to receive contrast)
Talk to your health care provider about your questions and concerns.
What the risks are
MRI contains no radiation. There have been no reported side effects from the magnetic fields and radio waves.
The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions to this dye are rare. However, gadolinium can be harmful to people with kidney problems that need 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 other pieces of metal inside your body to move or shift. For safety reasons, please don't bring anything that contains metal into the scanner room.
Chou R, Qaseem A, Owens DK, Shekelle P; for the Clinical Guidelines Committee of the American College of Physicians. Diagnostic Imaging for Low Back Pain: Advice for High-Value Health Care From the American College of Physicians. Ann Intern Med. 2011 Feb 1;154(3):181-189.
Wilkinson ID, Paley MNJ. Magnetic resonance imaging: basic principles. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 5.
C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.