The teaching material comprises four general, interrelated topics: Radiation exposure, dose, risk, and protection. A general overview of radiation units and dose descriptors is presented. Radiation doses are discussed in terms of patient imaging exams, including factors affecting radiation dose and associated image quality. Examples are given for typical diagnostic studies from radiography, fluoroscopy, interventional imaging, mammography, and CT. Radiation risks of x-ray exams are described in terms of immediate and long term, and examples of radiation risk are given to compare with a reference/standard, i.e., radiation risk from natural background radiation. Also, presented are radiation dose levels of potential concern - high fetal doses, skin doses from interventional imaging exams.