Diagnostic radiology, or diagnostic imaging, is the medical evaluation of body tissues and functions—both normal anatomy and physiology and abnormalities caused by disease or injury—by means of static (still) or dynamic (moving) radiological images.

The use of ionizing radiation in diagnostic radiology involves passing a localized beam of X rays through the part of the body being examined. This produces a static image on film. The image, called a radiograph, or X-ray picture, can take several forms. It may be a plain radiograph, such as the common chest X ray; a mammogram, an X-ray image of the female breast used to scan for cancerous tumors; a tomography, which produces an image of the entire depth of an anatomical structure with a series of X rays; or a computerized axial tomography (CT or CAT) scan, a computer analysis of a cross-sectional image of the body.