CT - Computed Tomography

You may have a CT scan to further evaluate observations made by X-rays. CT scans best visualize the bony elements of the spine. These scans are used to diagnose common degenerative conditions such as spinal stenosis and disc degeneration, spondylolysis and spondylolisthesis, as well as congenital spinal abnormalitie, among others. CT scans provide your doctor with high contrast and detailed cross-sectional images of the spine and spinal soft tissues and make the difference between normal and diseased tissues easy to see. [figure 1 ] CT technology is also used to evaluate fractures and dislocations in areas of the body with complex anatomy, such as the spine. Vertebrae can develop very small fractures, called compression fractures, causing pain and potentially nerve and disc complications. Your physician may request that a fluid (radiopaque contrast medium) be administered intravenously immediately prior to the test to make the picture even more detailed.

Narrowed canal space

Figure 1: Narrowed canal space, or spinal stenosis,
from arthritic bone overgrowth (CT)

Patients having CT scans lie on a table which is then moved into a large tube, sometimes called a gantry, which is open at both ends. CT examination is commonly done for patients unable to have an MRI due to claustrophobia. The entire CT examination now takes no longer than a series of X-rays, usually about 5 or 10 minutes.

In CT scanning the body is exposed to a series of X-ray beams. The body area being examined is scanned in small increments, often called CT ïslicesÍ, as opposed to X-rays which deliver a single exposure to the body and the X-ray film. Numerical data for the CT is gathered by computer related to different tissue absorption of the X-rays. Because the information is numerical (unlike X-rays), it can be manipulated to reconstruct images in an infinite number of body planes, even in three dimensions. CT scans are sometimes called CAT scans (computed axial tomography).