Abstract
Various radiation dose quantities have been defined by ICRP (International Commission on Radiological Protection) and ICRU (International Commission on Radiation Units and Measurements) and the dose quantities should be properly used according to the purpose. In radiological practice, modality-specific dose indices are utilized, and the dose indices such as CTDI (computed tomography dose index) and DLP (dose length product) in x-ray CT examinations are used for the evaluation of x-ray output and quality control of CT scanners. The dose quantities such as organ dose and effective dose is used for the dose evaluation for patients in CT examinations. One of the methods of dose evaluation for patients is based on the measurements using small dosimeters implanted in various organ positions within an anthropomorphic phantom. Another method is based on Monte Carlo (MC) simulation of photon interactions within a computational phantom of human body and MC simulation for CT dose estimation requires information on the geometry of a CT scanner, scan parameters, and a computational phantom. This paper describes an outline of radiation dose quantities, dose indices used in CT examinations and methods of dose evaluation for the patients.
