When the spine is x-rayed the beams pass through the skin and underlying soft tissues (e.g. muscle, ligaments, tendons). When the beams meet bone (vertebra) it stops creating a white shadow on the film. A bone abnormality is reflected on the finished film. Shades of gray mirror the density of the different tissues. X-rays are best for looking at bone. They are not helpful for looking at soft trauma.
X-rays are widely used today and are often called radiographs. These tests are not performed at random. An x-ray would most likely be performed when spine or extremity pain (e.g. leg, arm) is severe or chronic and progressive. An x-ray may rule out particular problems involving bone and some soft tissue disorders. When an x-ray proves inconclusive additional tests may be ordered especially if something suspicious is detected.
CT Scan (Computerized Axial Tomography) or CAT Scan was developed in 1970. The CT Scan evolved from Tomograms; multiple x-rays taken at different levels to check the depth of an abnormality. The advent of computers in medicine has meant less radiation exposure and shorter study times. The CT Scan has become an important adjunct to x-rays. The CT Scan uses multiple x-ray beams projected at many angles in conjunction with computer resources to create three-dimensional cross-sectional images. Each image or picture reveals a different level of tissue that resembles slices.