Computed tomography has emerged as the "gold standard" for the diagnosis of a broad range of medical diagnoses. For cardiac imaging alone, the installation of CT scanners in US cardiology practices alone has tripled over the past 2 years. Patients who undergo cardiac CTA (computed tomography angiography) may be subjected to relatively high doses of ionizing radiation (ie. 4 times annual background radiation) during the diagnosis and management of coronary artery disease. Current radiation doses for cardiac CT examinations are comparable to the effective doses for patients undergoing nuclear stress tests or cardiac catheterization (ie. approximately 10-15 milliSieverts). In addition, non cardiac CT protocols, such as chest CT examinations for the evaluation of pulmonary arteries, thoracic and abdominal aorta, and lung nodules, are associated with significant radiation exposure. Many patients undergo repeated CT examinations over several years for such pathology. There is a growing public concern regarding the cancer risk associated with such radiation.