Medical Radiology uses imaging modalities to diagnose and treat diseases within the human body. Radiographs (roentgenographs, named after the discoverer of X-rays, Wilhelm Conrad Röntgen) are produced by transmitting X-rays through a patient.  The radiologist toolbox consists of X-ray radiography, ultrasound and computed tomography (CT).  Also, nuclear medicine which includes positron emission tomography (PET), magnetic resonance imaging (MRI) and fusion imaging to diagnose and treat diseases. Nuclear medicine imaging requires the administration of a radiopharmaceutical into a patient.  The radiopharmaceutical has an affinity for certain body tissues labelled with a radioactive tracer.  The most commonly used tracers are iodine-123, iodine-131, technetium-99m, indium-111, gallium-67, thallium-201 and fludeoxyglucose (18F-FDG).  Interventional radiology is minimally invasive medical procedures under the direction of imaging technologies.  Mammography and dual-energy X-ray absorptiometry (DXA) use low energy to evaluate breast cancer and osteoporosis, respectively.  Furthermore, fluoroscopy and angiography use X-rays to project images onto a fluorescent screen for diagnostic evaluation.