Targeted radiation energy modulation using Saba shielding reduces breast dose without degrading image quality during thoracic CT examinations

Abstract

ObjectiveBreasts dose during thoracic computed tomography examinations is a serious challenge and practical dose reduction strategies is needed. The bismuth shielding is an available method for dose reduction; however, its use is on debate due to degrading effects on image quality. The aim of this study is to explore and evaluate the efficiency of a new composition of the X-ray absorbing material to achieve a shield with a lower impact on image quality. Materials and MethodsDifferent shields were manufactured with combinations of various weight percentage of copper and bismuth. Dose reduction ratio and image quality were evaluated in phantom studies. A controlled trial with 20 female participants was conducted for image quality assessment. The shield with a lower impact on image quality, named Saba shielding, was used in the clinical trial. ResultsShielding by one (1 T) and three thickness (3 T) of the constructed shields reduced the mean entrance skin dose of breasts about 52% and 73%, respectively. The shield with a composition of 90% Cu and 10% Bi (Saba shielding) had the lowest while the shield with 100% bismuth had the highest degrading effect on image quality. The Saba shielding could provide 21% higher dose reduction than the Bi shielding at the equivalent image quality. The 1 T Saba shielding did not cause artifacts in the reconstructed images. ConclusionThe Saba shielding is flexible, cheap and user-friendly for shielding breasts in thoracic CT examinations while do not have the degrading effect of the Bi shielding on image quality.