Radiology, ray dee OL uh jee, is the field of medicine that uses X rays and other means to create images of structures and processes inside the body. These images aid in diagnosis and treatment of diseases and other disorders. Radiology includes the use of such imaging techniques as computed tomography (CT), fluoroscopy, magnetic resonance imaging (MRI), and positron emission tomography (PET). Medical procedures that involve ultrasound (high-frequency sound waves) are also part of radiology. Doctors who specialize in radiology are called radiologists.