Radiography, known to most people as x-ray, is the oldest and most frequently used form of medical imaging. For nearly a century, diagnostic images have been created by passing small, highly controlled amounts of radiation through the human body, capturing the resulting shadows and reflections on a photographic plate.

X-ray imaging is the fastest and easiest way for a physician to view and assess broken bones, cracked skulls and injured backbones. At least two films are taken of a bone, and often three films if the problem is around a joint (knee, elbow, or wrist). X-rays also play a key role in orthopedic surgery and the treatment of sports injuries. X-ray is useful in detecting more advanced forms of cancer in bones. Very early cancer findings require other methods.

Radiologists have developed alternative imaging methods that do not rely on radiation, such as ultrasound and magnetic resonance imaging (MRI). However, because x-ray was the first imaging modality, many people (and medical imaging professionals) continue to use the term "radiology" to include all types of imaging. Strictly speaking, though, radiology refers to the use of x-rays.