X-rays (Diagnostic) >>

The most common radiology test, x-rays are a form of radiation (like light or radio waves) that can be focused into a beam, much like a flashlight beam. Unlike a beam of light, however, x-rays can pass through most objects, including the human body.

When x-rays strike a piece of photographic film, they produce a picture. Dense tissues in the body, such as bones, block many of the x-rays and appear white on an x-ray picture. Less dense tissues, such as muscles and organs, block fewer of the x-rays (more pass through) and appear in shades of gray. X-rays that pass through air only appear black.

The chest x-ray is the most common type of x-ray test. It provides a picture of organs and structures within the chest, including the heart and lungs, the blood vessels associated with them, and the thin sheet of muscle just below the lungs (diaphragm). A chest x-ray can help detect problems with these structures and with the bones inside the chest, such as the ribs, collarbone, and upper part of the spine. However, a chest x-ray may not provide all the information needed to determine the cause of a problem. If the chest x-ray is abnormal, more specific x-rays or other tests are needed.

At WebMD, learn more about

abdominal xrays,

spinal xrays,

xrays of an extremity, and

facial xrays.

See also Today's Health.