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.
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 a number of 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.
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 usually lasts a few minutes.