Direct Quantification of Breast Dose During Coronary CT Angiography and Evaluation of Dose Reduction Strategies

OBJECTIVE. The purpose of this study was to quantify the absorbed radiation dose received by the adult female breast during coronary CT angiography (CTA) and to evaluate the effectiveness of various dose reduction strategies. MATERIALS AND METHODS. An adult female thoracic anthropomorphic phantom was scanned using eight different clinical coronary CTA protocols that varied in detector configuration (320 x 0.5 mm or 64 x 0.5 mm), x-ray tube activation (full R-R, 65% R-R, or 70-80% R-R), use of tube current modulation, and use of breast shields. Direct dosimetry measurements were performed using Gafchromic film to determine the absorbed breast dose. RESULTS. Retrospective helical data acquisition using a 64-detector array and a full cardiac cycle without dose modulation or breast shielding is associated with an average absorbed breast dose of 82.9 mGy. Optimization of coronary CTA technique using a 320-detector array and a 70-80% cardiac phase reduces the absorbed breast dose by 78.9% to 17.5 mGy, whereas breast shields used in isolation reduces breast dose by up to 46.8%. CONCLUSION. The implementation of clinically validated coronary CTA protocols using large-area detector acquisition and prospective ECG gating with limited x-ray tube activation results in substantial breast dose savings of up to 78.9% and should be used whenever possible in combination with bismuth breast shields to achieve further dose reduction.