Health Encyclopedia

Spine MRI

Definition

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 vertebrae (spine bones), 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 and computed tomographic (CT) scans, MRI does not use radiation. Instead, it uses powerful magnets and radiowaves. The magnetic field produced by an MRI forces certain 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 may 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 can not 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:

Brain aneurysm clips
Certain artificial heart valves
Inner ear (cochlear) implants
Older vascular stents
Recently placed artificial joints

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 prior to the scan.

When the MRI magnet is turned on, pens, pocketknives, and eyeglasses may fly across the room. This can be dangerous, so such 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 spinal canal, bony segments, and soft tissue. 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.

What abnormal results mean

Spine MRI may reveal disorders such as:

Additional conditions under which the test may be performed:

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. Allergic reactions to the substance rarely occur. The person operating the machine will monitor your heart rate and breathing as needed.

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.

Review Date:1/24/2007
Reviewed By:Stuart Bentley-Hibbert, M.D., Ph.D., Department of Radiology, Weill Cornell Medical Center, New York, NY. Review provided by VeriMed Healthcare Network.

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