An X-ray of the LS spine (lumbo-sacral spine) is a safe and painless test to visualise the area of the lower back which consists of five lumbar vertebrae (L1 to L5) and the sacrum (a triangular bone at the end of the spine). It also helps to visualise their intervertebral discs with the surrounding soft tissues like skin and muscles using small amount of radiation. The image is recorded on a special X-ray film. The X-ray image is black and white. Dense structures such as the bones, appear white and softer body tissues, such as the skin and muscles appear darker. The actual exposure time to radiation is usually less than a second, although the overall test may take 20-30 minutes.