An X-ray is a quick, painless test that captures images of the structures inside the body — particularly the bones.
X-ray beams pass through the body. These beams are absorbed in different amounts depending on the density of the material they pass through. Dense materials, such as bone and metal, show up as white on X-rays. The air in the lungs shows up as black. Fat and muscle appear as shades of gray.
For some types of X-ray tests, a contrast medium — such as iodine or barium — is put into the body to get greater detail on the images.






