A lumbosacral spine CT is a computed topography scan of the lower spine and surrounding tissues.

You will be asked to lie on a narrow table that slides into the center of the CT scanner. You will need to lie on your back for this test.

Once inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam in one continuous motion.)

Small detectors inside the scanner measure the amount of x-rays that make it through the part of the body being studied. A computer takes this information and uses it to create several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of organs can be created by stacking the individual slices together.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

In some cases, an iodine-based dye, called contrast, may be injected into your vein before images are taken. Contrast can highlight specific areas inside the body, which creates a clearer image.

In other cases, a CT of the lumbosacral spine may be done after injecting contrast dye into the spinal canal during a lumbar puncture, to further check for pressure on the nerves.

The scan will usually last a few minutes.

You should remove all jewelry or other metal objects before the test, as they may cause inaccurate images.

The x-rays are painless. Some people may have discomfort from lying on the hard table.

Contrast may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

CT rapidly creates detailed pictures of the body. A CT of the lumbosacral spine is an excellent tool for evaluating fractures and degenerative changes of the spine, such as those due to arthritis.

CT of the lumbosacral spine may reveal the following conditions or diseases:

• Cyst
• Herniated disk
• Infection
• Metabolic disease
• Neoplastic disease (new abnormal tissue formation)
• Osteoarthritis
• Osteomalacia
• Pinched nerve
• Tumor
• Vertebral fracture

The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, hives, itching, nausea, breathing difficulty, or other symptoms may occur.

If you have diabetes or are on kidney dialysis, talk to your health care provider before the test about your risks.

CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. CT scans do create low levels of ionizing radiation, which have the potential to cause cancer and other defects. However, the risk associated with any individual scan is small. The risk increases as numerous additional studies are performed.

In some cases, a CT scan may still be done if the benefits greatly out weigh the risks. For example, it can be more risky not to have the exam, especially if your health care provider thinks you might have cancer.

Pregnant or breastfeeding women should consult their health care provider about the risk of CT scans to the baby.

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