Investigation of pediatric backscatter factor with an anthropomorphic phantom

Abstract

Abstract Background Entrance surface dose (ESD) is used to establish diagnostic reference levels (DRLs), which require a backscatter factor (BSF) for calculation. However, as no studies on pediatric BSF exist, adult BSF is currently used in pediatric ESD calculations. Objective The aim of this study was to derive a BSF using a pediatric phantom and conduct a comparison with BSFs derived from adult phantoms and existing data in general radiography. Materials and methods Incident air-kerma at the surface of a pediatric anthropomorphic phantom was measured using a set of optically stimulated luminescent dosimeters (OSLDs). Measurements were obtained using nanoDot OSLDs under different beam qualities and field sizes in three body regions, at a focal–surface distance of 100 cm. Air-kerma was measured using a set of nanoDots in the same positions in the absence of the phantom, and BSF was calculated using the two sets of data. The pediatric BSF values were compared with those obtained from adult phantom and existing data. Results BSF values were significantly lower for the pediatric phantom than for the adult phantom and were lowest in the chest (16%) under specific conditions and the greatest discrepancies of BSF values was found in PMMA tissue (19%) on every tube voltage when compared with the existing data. Conclusion Based on data obtained for the three body parts investigated, pediatric ESD should be calculated using human shaped pediatric anthropomorphic phantom rather than adult using adult and existing data.