Diagnostic Radiology is a subject or specialty that uses medical imaging to diagnose and treat diseases within the body. A variety of imaging techniques such as X-ray radiography, ultrasound, computed tomography (CT), nuclear medicine including positron emission tomography (PET), and magnetic resonance imaging (MRI) are used to diagnose and/or treat diseases. The exams often use radiation, at levels that have been determined to be safe, to create detailed anatomical images.