Patient dose in CT angiography examinations: An institutional survey

Abstract

This study aims to evaluate the radiation dose during five computed tomography angiography (CTA) examinations performed with a GE Light Speed 16 (16-slice) and a Toshiba Aquilion Prime 80 (80-slice) CT system and to establish institutional DRLs (IDRLs). The volume computed tomography dose index (CTDIvol), dose length product (DLP) per examination, patients' demographic and anatomical data, and technical data were retrospectively recorded for 240 adult patients. The effective dose (ED) was calculated based on the recorded DLP values and suitable conversion coefficients. The 75th percentiles of the distribution of the CTDIvol and DLP values were proposed as IDRLs. The radiation dose values were compared to corresponding previously published international data. For the GE system, the IDRLs were 15.6 mGy and 1041 mGycm for thoracic aorta, 18.1 mGy and 1691 mGycm for abdomen aorta, and 12.1 mGy and 407 mGycm for pulmonary arteries, in terms of CTDIvol and DLP values, respectively. For the Toshiba system, the IDRLs were 34.9 mGy and 845 mGycm for the brain, 6.5 mGy and 280 mGycm for carotids, 5.3 mGy and 218 mGycm for thoracic aorta, 7.7 mGy and 425 mGycm for abdomen aorta, and 7.2 mGy and 196 mGycm for pulmonary arteries, in terms of CTDIvol and DLP values, respectively. The mean ED values were 12.6 mSv for thoracic aorta, 20.4 mSv for abdomen aorta, and 4.9 mSv for pulmonary arteries, as well as 1.7 mSv for the brain, 2.5 mSv for carotids, 2.6 mSv for thoracic aorta, 5.3 mSv for abdomen aorta, and 2.2 mSv for pulmonary arteries examinations, for the GE and Toshiba systems, respectively. A reduction of 48–64% and 55–79% was reported for the mean CTDIvol and DLP values obtained with the Toshiba compared to the GE system (Mann-Whitney test p < 0.0001), due to the implementation of dose-saving technologies, such as lowered tube voltage and iterative reconstruction algorithm. The Toshiba system's IDRLs and ED values were comparable or lower than those reported in most of the previously published studies. There are significant variations in patient doses during CTA examinations, due to the CT systems' differences, scanning parameters and departmental CTA protocols utilised. Patient dose surveys could highlight the necessity of increasing the awareness and knowledge of the radiation dose levels during CTA examinations, to prompt dose optimisation strategies in CT facilities.