A CT scan is a type of X-ray that produces detailed cross-sectional images of your body. CT scans are used to diagnose and stage many types of cancers, including cancer of the lumbar spine (lower back). A CT scan of the lower spine without dye is used to create images of the bones and surrounding tissues in the lower back. The CT scan can help determine the size and location of any tumors in the lower spine and whether they have spread to nearby tissues.