A myelogram is a diagnostic imaging procedure done by a radiologist. It uses a contrast dye and X-rays or computed tomography (CT) to look for problems in the spinal canal, including the spinal cord, nerve roots, and other tissues. CT or CAT scan is a diagnostic imaging procedure using a combination of X-rays and computer technology to produce horizontal, or axial, images of the body. These images, called slices, show detailed images of the spinal canal. CT scans provide more detail than standard X-rays.