PShield: An exact three-dimensional numerical solution for determining optimal shielding designs for PET/CT facilities
Layout of the scenario described in example 1. Four source locations (S 1–S 4), two shielded barriers (B 1 and B 2), and the dose delivered to a single control point (C 1) were considered. The control point was located in a controlled corridor with a design dose rate of 100 μSv/wk.
Layout of the scenario described in example 2. The green X marks the assumed limiting exposure and calculation point for TG 108 shielding requirements for B 1. The orange X marks the actual limiting exposure point as determined by the numerical solution of the NLP problem using the PShield method.
Results from example 1. (a) The set of all solutions resulting in achievement of the design dose at C 1 in example 1. (b) The cost function (total shielding mass) applied to the solution set in part (a) plotted versus the thickness of B 1. At any point in the plot, the thickness of B 2 can be determined by relating B 1 to B 2 in part (a).
Illustration of the path taken by a technologist traveling down the corridor in example 2.
Calculated dose rates along the path outlined in Fig. 4. The reference points on the ordinate correspond to the reference locations in Fig. 4. Dose rates resulting from use of the PShield design (red line) are compared with dose rates resulting from the use of the manual Rule Based Method (black line). The dose rates between reference points 6 and 7 are also plotted using the manual Rule Based Method in the absence of source 5 (green line). The design dose of 100 μSv/wk is added as a reference (dark blue line).
Definition of key symbols and notation.
Source definitions for example 1.
Source definitions for example 2.
Application of Eqs. (1) and (2) to the source definitions in example 1.
Application of manual Rule Based Method defined in the Methods section.
Output of the PShield algorithm for example 2, including differences in calculated shielding thicknesses compared to the manual Rule Based Method.
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