Assessment of breast absorbed doses during thoracic computed tomography scan to evaluate the effectiveness of bismuth shielding

Abstract

During a lung computed tomography (CT) examination, breast and nearby radiosensitive organs are unnecessarily irradiated because they are in the path of the primary beam. The purpose of this paper is to determine the absorbed dose in breast and nearby organs for unshielded and shielded exposures with bismuth. The experiment was done with a female anthropomorphic phantom undergoing a typical thoracic CT scan, with TLD-100 thermoluminescent detectors insert at breast, lung and thyroid positions. Results showed that dose reduction due to bismuth shielding was approximately 30% and 50% for breast and thyroid, respectively; however, the influence of the bismuth on the image quality needs to be considered. - Highlights: • Organ dose reduction in CT examinations is a concern to minimize radiation risks. • Some organs are unnecessarily exposed to radiation during CT scans. • Reduction of absorbed dose in breasts and nearby organs during thoracic CT with bismuth shielding was studied. • Bismuth shielding proved to be a simple procedure to reduce significantly the absorbed dose in organs. • The influence of the bismuth shielding on the CT image quality should be taken into account.