An X-ray can be done on the chest, abdomen, pelvis, skull and limb. It involves exposing a part of the body to a small dose of radiation to produce an image of the internal organs. When x-rays penetrate the body, they are absorbed in varying amounts by different parts of the anatomy. Ribs and bones, for example, will absorb much of the radiation and, therefore, appear white or light grey on the image. Lung tissue and other internal organs absorb lesser radiation and appear darker on the image. In this manner, a “picture” of the body part is formed. For some types of X-ray tests, a contrast medium — such as iodine or barium — is introduced into your body to provide greater detail on the images.