The spine consists of 33 bones, most of which are separated by discs that act as cushions for the bones. The spinal cord is surrounded by the bones of the spine (vertebrae) and a sac containing cerebrospinal fluid (CSF).
A spinal computed tomography (CT) scan is a special type of X-ray test that produces detailed pictures of the spine and vertebrae in the neck (cervical spine), upper back (thoracic spine), or lower back (lumbosacral spine). More detailed evaluation of an area may require additional sessions. A CT scan is also called a computerized axial tomography (CAT) scan.
A CT scanner directs a series of X-rays through the body that are analyzed by a computer to produce a detailed picture of a "slice" of an organ or area being studied. Each X-ray pulse lasts only a fraction of a second, and it takes only a few seconds for the machine to record each slice. Information from a CT scan can be saved and stored on a computer for further study. Photographs of selected views can also be made.
Dense tissues, such as bones, appear white in the pictures produced by a CT scan. Less dense tissues, such as the spinal cord, appear in shades of gray. The spinal canal containing cerebrospinal fluid appears dark gray.
During a CT scan of the spine, you are positioned inside a cylinder that is part of the CT scanner. The cylinder can tilt and the X-ray scanning devices within it can rotate to obtain the views needed.
In some cases, contrast material may be given intravenously or into the canal next to the spinal cord (intrathecally) to enhance the images of certain structures. The contrast material may help evaluate blood flow, detect some types of tumors, and locate areas of inflammation or nerve damage.
Why It Is Done
A CT scan of the spine is done to:
- Examine the bones of the spine (vertebrae).
- Further evaluate problems discovered during a conventional X-ray test.
- Detect problems of the spine, such as tumors, injuries (especially fractures), deformities, or narrowing of the spinal canal (spinal stenosis).
- Identify a ruptured (herniated) disc of the spine.
- Help determine whether complications of osteoporosis are present.
- Evaluate problems of the spine that have been present since birth (congenital).
- Monitor the success of spinal surgery or therapy.