Radiology is the medical discipline that uses medical imaging to diagnose and treat diseases within the bodies of animals, including humans.

A variety of imaging techniques such as X-ray radiography, ultrasound, computed tomography (CT), nuclear medicine including positron emission tomography (PET), fluoroscopy, and magnetic resonance imaging (MRI) are used to diagnose or treat diseases. Interventional radiology is the performance of usually minimally invasive medical procedures with the guidance of imaging technologies such as those mentioned above.

The modern practice of radiology involves several different healthcare professions working as a team. The radiologist is a medical doctor who has completed the appropriate post-graduate training and interprets medical images, communicates these findings to other physicians by means of a report or verbally, and uses imaging to perform minimally invasive medical procedures.  The nurse is involved in the care of patients before and after imaging or procedures, including administration of medications, monitoring of vital signs and monitoring of sedated patients. The radiographer, also known as a "radiologic technologist" in some countries such as the United States and Canada, is a specially trained healthcare professional that uses sophisticated technology and positioning techniques to produce medical images for the radiologist to interpret. Depending on the individual's training and country of practice, the radiographer may specialize in one of the above-mentioned imaging modalities or have expanded roles in image reporting.

X-ray tube generates a beam of X-rays, which is aimed at the patient. The X-rays that pass through the patient are filtered through a device called a grid or X-ray filter, to reduce scatter, and strike an undeveloped film, which is held tightly to a screen of light-emitting phosphors in a light-tight cassette. The film is then developed chemically and an image appears on the film. Film-screen radiography is being replaced by phosphor plate radiography but more recently by digital radiography (DR) and the EOS imaging.[5] In the two latest systems, the X-rays strike sensors that converts the signals generated into digital information, which is transmitted and converted into an image displayed on a computer screen. In digital radiography the sensors shape a plate, but in the EOS system, which is a slot-scanning system, a linear sensor vertically scans the patient.

Plain radiography was the only imaging modality available during the first 50 years of radiology. Due to its availability, speed, and lower costs compared to other modalities, radiography is often the first-line test of choice in radiologic diagnosis. Also despite the large amount of data in CT scans, MR scans and other digital-based imaging, there are many disease entities in which the classic diagnosis is obtained by plain radiographs. Examples include various types of arthritis and pneumonia, bone tumors (especially benign bone tumors), fractures, congenital skeletal anomalies, and certain kidney stones.