SU‐DD‐A4‐05: Fits of the NT/(Pd2) Shielding Curves in NCRP Report Number 147
Abstract
Purpose: The diagnostic x‐ray shielding requirements for Radiographic and R&F rooms presented in Figs. 4.5 through 4.8 in NCRP Report No. 147, and for cardiac angiography labs, have been fit to a three‐parameter equation that relates the barrier thickness x to the value of NT/(Pd2). The locations of the source in the imaging room appropriate to the determination of distance d are also explicitly presented. Methods and Materials: Section 4.2.4 of NCRP‐147 presents lead and concrete shielding requirements for barriers around “representative” Radiographic and R&F rooms that include contributions from all clinical beam locations and directions. The required shielding thickness, x, for the various barriers around each room is presented graphically as a function of NT/(Pd2), where N is the weekly number of patients, T is the occupancy, P is the permitted weekly air kerma, and d is the distance (in m) from an x‐ray source to the occupied area. This method has been applied previously to cardiac angiography labs. Letting η0 be the maximum value of NT/(Pd2) for which no shielding is required, barrier thickness x depends on (NT)/(Pd2) following the equation of Archer et al. (1983): urn:x-wiley:00942405:media:mp0330:mp0330-math-0001 Results: The values of NT/(Pd2) (mGy−1 m−2) have been fit to Eq. 1 as a function of x for the curves in Figs. 4.5 through 4.8 of NCRP‐147, and for cardiac angiography labs. The resultant values of η0, α, β, and γ for lead and concrete barriers are presented.…
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