A lumbar magnetic resonance imaging (MRI) scan uses energy from strong magnets to create pictures of the lower part of the spine (lumbar spine).
An MRI does not use radiation (x-rays).
Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces many images.
Related exams include:
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). Make sure you take off your watch, jewelry and watches. 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 to 60 minutes, but may take longer.
How to Prepare for the Test
You may be asked not to eat or drink anything for 4 to 6 hours before the scan.
Tell your health care provider if you are afraid of closed spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious. Your provider may suggest an "open" MRI, in which the machine is not as close to the body.
Before the test, tell your 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)
- Recently placed artificial joints
- Certain types of vascular stents
- Worked 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 Feel
An MRI exam causes no pain. You will need to lie still as too much movement can blur MRI images and cause errors.
The table may be hard or cold, but you can ask for a blanket or pillow. The machine makes loud thumping and humming noises when turned on. You can wear ear plugs to help block out the noise.
An intercom in the room lets you to speak to someone at any time. Some MRIs 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. After an MRI scan, you can return to your normal diet, activity, and medicines.
Why the Test is Performed
You may need a lumbar MRI if you have:
- Low back pain that does not get better after treatment
- Leg weakness, numbness, or other symptoms that do not improve or get worse
Your provider may also order a lumbar MRI if you have:
- Back pain and fever
- Birth defects of the lower spine
- Injury or trauma to the lower spine
- Low back pain and a history or signs of cancer
- Multiple sclerosis
- Problems controlling or emptying your bladder
- Disc herniation
A normal result means your spine and nearby nerves look okay.
What Abnormal Results Mean
Most of the time, Abnormal results are due to:
- Herniated or "slipped" disk (lumbar radiculopathy)
- Narrowing of the spinal column (spinal stenosis)
- Abnormal wearing on the bones and cartilage in the spine (spondylitis)
Other abnormal results may be due to:
- Ankylosing spondylitis, a type of arthritis
- Bone infection
- Cauda equina syndrome
- Fractures of the lower back due to osteoporosis
- Disk inflammation (diskitis)
- Spinal cord abscess
- Spinal cord injury
- Spinal tumor
Talk to your provider about your questions and concerns.
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 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 do not bring anything that contains metal into the scanner room.
Magnetic resonance imaging - lumbar spine; MRI - lower back
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Review Date 3/5/2015
Updated by: C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.