What’s the Difference Between MRIs and CT Scans When Considering Back Surgery?

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When you’re experiencing severe back pain and you’ve tried everything, you may need spinal surgery. This means an MRI or CT scan may be ordered. For those without a medical background, it can be difficult to understand the ins and outs, even when explained by a physician. It sounds scary and serious, but what exactly are these procedures, what is the difference between them and what will they show?

CT scans can provide extremely detailed images, offering tremendous benefits toward an accurate diagnosis. About 68 million of these procedures are performed in the U.S. each year, USA Today reports. An MRI is also an important diagnostic tool, which can access bulging, degenerated or herniated discs to support spine surgery planning. In 2011, 32 million MRI scans were performed, according to Medtronic.

CT Scans

A CT scan (computerized tomography) is a series of X-rays taken from a number of various angles and computer processing to create cross-sectional images of the bones and soft tissues in the body. The machine circles the body to scan an area from each angle within that circle. It measures how much the X-ray beams change while passing through the body, and then relays the information to the computer in order to generate a series of black and white images. This procedure tends to do a better job of showing internal organs in the abdominal area than details of the bones in the spine, but because some back pain can be the result of problems with the pancreas or kidney, it can be helpful, according to Harvard Medical School.

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The test usually takes about 30 to 45 minutes and is not painful, though some patients get a little uncomfortable from being in the same position for an extended period of time. The radiologist may be able to provide preliminary results within a day, while the formal reading takes an additional day.


An MRI does not use any radiation, like an X-ray or a CT scan does. It uses radio waves, a large magnet and a computer to create images of organs and structures within the body. Each picture provides a different cross-section of the area viewed, providing a very detailed representation of a specific area. An MRI of the spine shows intricacies of the nerves, vertebrae, vertebral discs, spinal cord and muscles.

During the procedure, you’ll lie on your back on a narrow table that is moved back and forth into a tunnel where the MRI scans are taken. It generally takes anywhere from 30 to 90 minutes and is not painful, though some patients who feel uneasy in tight spaces may be given anti-anxiety medicine to induce relaxation.

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As the MRI images are typically recorded on film, it takes at least an hour for them to be developed, plus additional time for the physician to examine and interpret them. Preliminary results may be available within a day or two, with complete results normally taking anywhere from four to seven days.

Can an MRI or CT Scan Determine Necessity of Back Surgery?

In most cases, MRI and CT scans are important diagnostic tools, but many clinics and providers consider them to be just one factor in the process of determining whether or not a patient is a good candidate for spinal surgery. They can provide a good indication, but generally, in-person evaluations are critical for determining optimal treatment methods, Laser Spine Institute says.