Establishment of institutional diagnostic reference levels for 6 adult computed tomography examinations: Results from preliminary data collection

Computed tomography (CT) is the leading source of the cumulative effective doses to the general populace from medicinal and artificial sources. With the increased use of CT examinations comes the concern regarding the health effects of unnecessary radiation exposure and the need to optimize the doses that patients receive. The current study evaluates the patients' doses during specific CT procedures and establishes institutional diagnostic reference levels (DRLs) for the frequent CT scans performed. 8156 CT scan examinations were performed during three years from 2015 to 2018 using a single CT scan machine at our institution. Data from the six most common examinations were analyzed. The volume CT dose index (CTDIvol (mGy)) and dose length product (DLP) distribution's median and 75th percentile values were computed. The results were descriptively compared with DRLs from different countries and regions. The six most common examinations constituted 5815 studies. We established our DRLs as the median value of CTDIvol (mGy)| and DLP (mGy × cm) as follows: CT of the brain: 35.0 mGy and 839 mGy× cm, respectively; chest with contrast: 4 mGy and 148 mGy-cm, respectively; chest without contrast: 5 mGy and 190 mGy-cm, respectively; abdomen and pelvis with contrast: 8 mGy and 636 mGy-cm, respectively; abdomen and pelvis without contrast 8 mGy and 568 mGy-cm, in that order; abdomen, pelvis, and kidneys: 11 mGy and 458 mGy× cm, respectively. Our values for brain and chest CTs were lower than the international DRLs, while those for abdominal imaging were higher. The established DRLs offer an opportunity for us to optimize the dose delivered to patients and compare them to the national benchmarks when they are issued. The study revealed that CT dose showed wide discrepancies for the same procedures at the department levels suggesting that the practice was neither optimized nor harmonized. Therefore, DRL should be reassessed after the operators' training and awareness to reduce the patients' dose and related radiogenic risk to its minimal value.