Patient dose audit in common CT examinations

Abstract

A dose audit was performed to evaluate the radiation dose to 573 adult patients, who underwent eleven common CT examinations in two different CT scanners: one with 16 detector rows (GE Light Speed 16) and one with 80 detector rows (Toshiba Aquilion Prime 80). The volume computed tomography dose index (CTDIvol), dose length product (DLP), as well as patients’ demographic and technical data were recorded. The 75th percentiles of the distribution of the CTDIvol and DLP values were proposed as institutional (local) diagnostic reference levels (IDRLs) and were compared to corresponding national (NDRLs) and international values. All dose values are based on the 32-cm body phantom, except for the head, sinuses and auditory canal examinations in Toshiba system, as well as the head and neck examinations in GE system where the 16-cm head phantom is used. A reduction of up to 67% and 64% (Mann-Whitney test p < 0.05) was reported for the mean CTDIvol and DLP values obtained with the Toshiba system compared to the GE system. The IDRLs for the Toshiba system were lower up to 71% and 68% compared to the corresponding NDRLs in terms of CTDIvol and DLP values, respectively. For the GE system, the IDRLs regarding the CTDIvol values were lower up to 23% and 39% compared to the corresponding NDRLs, except for the skull base examination that exceeded up to 112%, as well as for the head and lumbar spine examinations that were exceeded 10%, regarding the DLP values. The effective dose (ED) was also calculated based on the recorded DLP values and suitable conversion coefficients. The mean ED values for the GE system were 2.15 mSv for the head (1.28 mSv for the brain and 0.87 mSv for the skull base), 2.95 mSv for the neck, 10.1 mSv for the lumbar spine, 5.67 mSv for the chest, and 8.36 mSv for the abdomen. For the Toshiba system, the mean ED values were 1.74 mSv for the head, 2.02 mSv for the neck, 9.59 mSv for the lumbar spine, 2.03 mSv for the chest, 5.62 mSv for the abdomen, and 2.71 mSv for the pelvis. These values were comparable to or lower than those reported in most of the international studies previously published. Patient dose surveys could contribute towards optimising radiation protection for patients, therefore, highlighting the necessity to increase the awareness and knowledge of the radiation dose levels during common CT examinations.