The impact of gonad shielding in anteroposterior (AP) pelvis projections in an adult: A phantom study utilising digital radiography (DR).

ABSTRACT

INTRODUCTION: Positioning relative to the lateral automatic exposure control (AEC) chambers (cranial/caudal orientation) optimises dose and image quality in pelvic radiography. In the cranial orientation introducing gonad shielding (GS) in females may increase radiation dose. The aim of this study was to fully optimise the combination of pelvis orientation and use of GS in both male and females. METHODS: An anthropomorphic pelvis phantom was exposed, with dose area product (DAP) recorded, in both orientations without GS and four conditions with GS cranial orientation (female/male), caudal orientation (female/male). A 4 cm × 4 cm grid incorporating thirteen positions for the GS resulted in 52 experimental settings. Blind image quality assessment, utilising a modified scale, was undertaken by two experienced observers. RESULTS: Comparing no GS (caudal orientation) to female GS, no significant change in DAP was seen (3.97 v 4.03 dGy*cm2; Mann-Whitney p = 0.060). Comparing no GS (cranial orientation) to male GS no significant change in DAP was seen (8.66 v 8.77 dGy*cm2; Mann-Whitney; p = 0.210). DAP increased significantly with introduction of female GS in the cranial orientation (23% 8.66 v 10.65 dGy*cm2, Mann-Whitney; p < 0.001) and male GS in the caudal orientation (22.8% 3.97 v 4.87 dGy*cm2, Mann-Whitney; p < 0.001). Significantly higher repeat rates (Chi-squared test; p < 0.001) were seen for GS in female (85-100%) compared to male (30.8%). CONCLUSION: The use of gonad shielding can increase DAP and lead to repeats being required, with more required for female GS usage, suggesting the utility of GS for pelvis examinations is questionable. IMPLICATIONS FOR PRACTICE Optimisation of radiation dose in pelvic radiographic examinations utilising AEC terminated exposures requires consideration of AEC chamber position and GS usage.