Modelling and optimization of dosimeters in the product box for commissioning dosimetry at gamma irradiator using Voronoi Diagram algorithm

Abstract

The complexity of the geometrical configuration of a product box and source rack demands an efficient and straightforward methodology for positioning dosimeters in desired planes of the product box to optimise its dose profile. The gamma dose profile generated in the Y-set of commissioning dosimetry depends on the geometry of the selected planes of the product box. The present work attempts to model a product box using a Voronoi diagram-based algorithm for optimising the number of dosimeters in the desired planes of the product box. Discrete dosimeter positions in vertical planes of the product box were used to construct the Voronoi diagram and Delaunay triangulation to model the product box. The Voronoi vertices were computed using a perpendicular bisector algorithm from the discrete coordinates of positions of dosimeters. The Voronoi vertices of the plane of the product box were chosen to optimise the position of dosimeters. The ceric-cerous dosimeters were used to measure the absorbed doses in the product box to validate the algorithm. The overdose ratio calculated was estimated as the average maximum dose and the average minimum dose from the vertices of the Voronoi diagram, and the position of dosimeters put as per conventional strategy in the plane of the product box. The results estimated from the proposed methodology are very close to the conventional dosimetry with a better dose uniformity ratio. The overdose ratio calculated from the Voronoi approach (DUR = 1.06) was found to be improved compared to the estimated overdose ratio (1.07) of the conventional Z-set dosimetry. The present work established the advantages of using the Voronoi Diagram in commissioning dosimetry to ease the dosimetry process.