Magnetic Resonance Imaging (MRI) - Spine

• What is MRI of the Spine?
• What are some common uses of Spine MRI?
• How is the MRI performed?
• Who interprets the results and how do I get them?
• What are the limitations of MRI of Spine MRI?
• What are the benefits vs. risks?

What is MRI of the Spine?

Magnetic resonance imaging (MRI) is a non-invasive imaging method that uses radio waves and a powerful magnetic field rather than x-rays to produce clear and detailed images of virtually any part of the body. This procedure has greatly improved the ability to visualize normal and diseased tissue in and around the spine. MRI is most frequently used to determine the etiology of neck, lowback and radiating extremity pain. MRI of the spine also used to evaluate tumors and neurologic conditions. The examination shows the anatomy of the vertebrae and discs that make up the spine, as well as the spinal cord and the neural foramen (the spaces between the vertebrae through which nerves pass.) MRI requires specialized equipment to perform properly and the radiologist's expertise to correctly interpret the findings.

What are some common uses of Spine MRI?

Perhaps the most common reason for spinal MRI is to detect a bulging, degenerated or extruded intervertebral disc-a frequent cause of neck, lower back pain and radiculopathy/sciatica. Compressed (or pinched) and inflamed nerves are visible on MRI. In some cases the cause of nerve compression, whether from a herniated disc, arthritis or some other abnormality, also is demonstrated.

MRI is frequently done to help plan surgeries on the spine such as the decompression of a pinched nerve or spinal fusion. MRI is performed after spinal surgery to re-evaluate diseased discs and less frequently to look for post-operative scarring, bleeding or infection.

The MRI of the spine can help to diagnose-or exclude-spinal infection or tumors that arise in, or have spread to, the spine; the common tumors that spread to the spine include prostate, lung and breast cancers.

MRI is done before epidural steroids are injected for relief of pain. In this instance, MRI helps ensure that the medication will not be mistakenly injected into a tumor or site of infection.

How is the MRI performed?

A neuroradiologist, who is a physician experienced in head, neck and spine MRI examinations, will analyze the images and send a signed report with his or her interpretation to the patient's personal physician. A preliminary interpretation may be available shortly after the exam and a formal report of the complete results will be sent to the referring physician within a day. Your primary physician or the radiologist may discuss the findings of the MRI examination with you. New technology also allows for distribution of diagnostic reports and referral images over the Internet to our facility.

What are the limitations of MRI of Spine MRI?

MRI generally is not done in the first 12 weeks of pregnancy; however, in urgent situations it may be performed. Radiologists prefer to use other methods such as ultrasound imaging in pregnant women unless no examination other than MRI will do. It may not be possible to perform MRI in a very obese patient, although an open unit will work in most cases. The presence of an implant or other metallic object often makes it difficult to obtain clear images, and patient movement can have the same effect. A patient with severe pain may not be able to lie still during imaging. The MRI findings by themselves do not establish an absolute diagnosis, but in most situations the findings will suggest the correct diagnosis. The images must be interpreted along with the patient's history, physical findings and information from other tests. Vertebral fractures may be better detected by CT scanning. MRI may be more costly than other imaging methods, including CT scanning.

What are the benefits vs. risks?

Benefits:

• MRI is an excellent method of obtaining clear, detailed images of the bony structures and soft tissues of the spine, including the spinal cord. It demonstrates abnormalities, injuries and diseases in the spinal region that may not be visualized with other imaging methods.

• MRI is a noninvasive study that-unlike conventional x-rays, CT scanning and myelography-does not require exposure to ionizing radiation.

• This method takes little time to carry out, making it very useful for evaluating people who have been injured. It is especially helpful for diagnosing or ruling out acute compression of the spinal cord when clinical examination shows muscle weakness or paralysis.

• The contrast material sometimes used for MRI does not contain iodine, and therefore is far less likely to produce an allergic reaction than the contrast materials used for conventional x-rays and CT scanning.

• MRI is able to detect subtle changes in the vertebral column that may be an early stage of infection or tumor. The procedure may be better than CT or bone scans for evaluating tumors, abscesses and other masses near the spinal cord..

Risks:

• There are no definite side effects from any type of MRI study, including MR angiography.

• An undetected metal implant may be affected by the magnetic field. The procedure should be avoided in any patient with a pacemaker, implanted neurostimulator, certain types of metallic ear implants (cochlear implants) or metallic object within the eye socket. It should also be avoided if the patient has a port for delivering insulin or chemotherapy (however, many ports are detachable so patients can safely undergo MRI examinations).

• MRI is generally avoided in the first 12 weeks of pregnancy. Doctors usually use other methods of imaging, such as ultrasound, on pregnant women unless there is a strong medical reason.

• Women who are breast-feeding should inform the radiologist and ask how to proceed. If necessary they may pump breast milk before the exam for use until the gadolinium contrast material has cleared from the body, about 24 hours.

Copyright © 2005 Radiological Society of North America, Inc.
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