X-ray specialists are medically known as radiologists. They are medical doctors who specialize in diagnosing and treating diseases and injuries using medical imaging technology known as radiology, including the use of x-rays, magnetic resonance imaging (MRI), computed tomography (CT), nuclear medicine, ultrasounds, and positron emission tomography (PET). Radiologists will complete a minimum of 13 years of training. This will include medical school, a four-year residency, and usually an additional 1-to-2-year fellowship to complete their specialized training, such as interventional radiology, radiation oncology, or pediatric radiology. Radiologists are certified doctors through the American Board of Radiology and have exacting requirements for continuing medical education throughout their practicing years.