"Recommendations of the National Council on Radiation Protection and Measurements."

Report No. 147 (2004) presents recommendations and technical information related to the design and installation of structural shielding for facilities that use x rays for medical imaging. The purpose of structural shielding is to limit radiation exposure to employees and members of the public. The information supersedes the recommendations that address such facilities in NCRP Report No. 49, Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies Up to 10 MeV, which was issued in September 1976. NCRP Report No. 147 includes a discussion of the various factors to be considered in the selection of appropriate shielding materials and in the calculation of barrier thicknesses. The Report presents the fundamentals of radiation shielding, discusses shielding design goals for controlled and uncontrolled areas in or near x-ray imaging facilities and defines the relationship of these goals to the NCRP effective dose limits for radiation workers and members of the public. The Report includes a detailed discussion of the recommended shielding design methodology for x-ray imaging facilities and provides an extensive collection of shielding data and sample shielding calculations for various types of x-ray imaging facilities. The Report is mainly intended for those individuals who specialize in radiation protection. However, it will also be of interest to architects, hospital administrators and related professionals concerned with the planning of new facilities that use x rays for medical imaging.

NCRP Report No. 116 is the latest in the long series of reports on basic radiation protection criteria that began in 1934. It supersedes the predecessor in the series, NCRP Report No. 91, which was published in 1987. The current Report takes advantage of new information, evaluations and thinking that have developed since 1987, particularly the risk estimate formulations set out in NCRP Report No. 115. While the recommendations set out in this Report do not constitute a radical revision of the basic criteria, they do represent a refinement of the system enunciated in Report No. 91. Important changes include the utilization of revised tissue/organ weighting factors and the introduction of radiation weighting factors. Also noteworthy is the introduction of an allowable reference level of intake. Noteworthy too is the recommendation of an age-based lifetime limit for control of occupational exposures and a major simplification of limits aimed at controlling the exposure of the embryo and fetus. This Report, after outlining the goals and philosophy of radiation protection and the basis for exposure limits, goes on to review, in some detail, absorbed dose, equivalent dose, radiation weighting factors, and effective dose. Committed equivalent dose and committed effective dose are also introduced. Risk estimates for radiation exposure are presented and then the dose limits are enunciated. The Report also covers exposure in excess of the limits, limits for unusual occupational situations, guidance for emergency occupational exposure, and remedial action levels for naturally occurring radiation.

"The purpose of this Report is to provide guidance to researchers in preparing protocols that include ionizing radiation exposure to human subjects and to provide guidance to reviewing bodies, such as Institutional Review Boards, in the process of reviewing such protocols. This includes guidance for assessing proper utilization of radiation, estimation of risk, optimization of radiation dose, and formulation of informed consent statements with consistent, comprehensible and accurate language"--