Magnetic resonance imaging (MRI) of the spine is a noninvasive procedure that uses powerful magnets and radio waves to create pictures of the spine area, including the spine bones (vertebrae), the spinal cord, and the spaces between the vertebrae through which the nerves travel.
Alternative Names: Magnetic resonance imaging - spine; Nuclear magnetic resonance - spine; MRI of the spine; NMR - spine
How the test is performed:
You will be asked to lie on a narrow table, which slides into a large tunnel-like tube. The health care provider may inject a dye through one of your veins. This helps certain diseases and organs show up better on the images.
Unlike computed tomography (CT) scans, MRI does not use radiation. Instead, it uses powerful magnets and radio waves. The magnetic field produced by an MRI forces atoms in your body to line up in a certain way. It's similar to how the needle on a compass moves when you hold it near a magnet.
The radio waves are sent toward these atoms and bounce back, and a computer records the signal. Different types of tissues send back different signals. For example, healthy tissue sends back a slightly different signal than cancerous tissue.
A technologist will operate the machine from a room next door and watch you during the entire study.
Several sets of images are usually needed. Each one takes about 2 - 15 minutes. A complete scan can take up to 1 hour. Newer scanners may complete the process in less time.
How to prepare for the test:
The strong magnetic fields created during an MRI can interfere with certain implants, particularly cardiac pacemakers. People with cardiac pacemakers cannot have an MRI and should not enter the MRI area.
If you have any of the following metallic objects in your body, you should not get an MRI:
You will be asked to sign a consent form that says you do not have any of these items in your body.
Before an MRI, sheet metal workers or any person that may have been exposed to small metal fragments should receive a skull x-ray to check for metal in the eyes.
MRI can easily be performed through clothing. However, because the magnet is very, very strong, certain types of metal can cause significant errors, called artifacts, in the images. Also, certain metallic objects are not allowed into 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.
Pens, pocketknives, and eyeglasses may fly across the room when the scanner is on. These items are not allowed into the scanner area.
How the test will feel:
An MRI exam causes no pain. Some people may become anxious when inside the scanner. If you have difficulty lying still or are very anxious, you may be given a mild sedative. Excessive movement can blur MRI 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. Ear plugs are usually given to help reduce the noise.
An intercom in the scanner allows you to speak to the person operating the exam 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 sedation was necessary. After an MRI scan, you can resume your normal diet, activity, and medications.
Why the test is performed:
Spine MRI may show the exact location of tumors or other problems of the spine, spinal cord, or disks.
It provides detailed pictures of hard-to-view areas of the spine, including the:
Bony segments
Soft tissue
Spinal canal
MRI works better than CT scan in evaluating abscesses , tumors, or other masses near the spinal cord. While CT is better at detecting fractures of the vertebrae, MRI can detect subtle changes in the bone that may be due to infection or tumor.
Spine MRI may be performed in emergency settings to rule out spinal cord damage when there is weakness or paralysis.
The sensitivity of MRI depends, in part, on the experience of the radiologist.
What the risks are:
There is no ionizing radiation involved in MRI, and there have been no documented significant side effects of the magnetic fields and radio waves used on the human body to date.
The most common type of contrast (dye) used is gadolinium. It is very safe. However, you should not receive gadolinium if you are pregnant because it can potentially harm your unborn baby. Allergic reactions to gadolinium rarely occur. The person operating the machine will monitor your heart rate and breathing as needed.
There have been recent reports of fibrotic skin diseases in patients with severe kidney failure who received MRI dye. If you have severe kidney failure, tell your doctor before the study.
People have been harmed in MRI machines when they did not remove metal objects from their clothes or when metal objects were left in the room by others.
Special considerations:
Review Date: 4/10/2008 Reviewed By: Benjamin Taragin, MD, Department of Radiology, Montefiore Medical Center, Bronx, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
