Determination of institutional dose levels for brain, neck, thorax, abdomen, and cardiac computed tomography examinations and comparison with national and international dose reference levels

Objective:Computed tomography (CT) is an imaging modality responsible for approximately 60% of medical radiation exposure and is increasingly used in clinical practice every day. This study aims to establish our institutional dose report by analyzing the dose reports from frequently performed brain, neck, thorax, abdomen, and cardiac CT examinations at our institution. It was initiated due to the absence of a systematic dose report study in our institution to date and the insufficient awareness of radiation dose management among radiology technicians, radiologists, and clinicians. The study seeks to systematically investigate our institution's radiation dose data, identify trends and potential areas for dose optimization, and assess compliance with national and international diagnostic reference levels (DRLs). Material and Method: In our study, contrast-enhanced and non-contrast enchanced brain, neck, thorax, and abdominopelvic CT examinations, along with retrospective ECG-gated coronary CT angiography, high-pitch prospective ECG-gated coronary CT angiography, Triple Rule-out CT angiography, and coronary artery calcium scoring examinations which performed on patients over 18 years of age, were retrospectively analyzed in a consecutive manner starting from May 31, 2024. Demographic data such as patient gender and age; protocol parameters such as mAs, kVp, and pitch value; and dose data such as CTDIvol and DLP were collected and analyzed. The dose data parameters were compared with national and international DRL values. Results: In our study, a total of 11,457 examinations from patients with a mean age of 53.6 ± 15.8, comprising 45% women and 55% men, were evaluated. The proportion of female patients was higher in neck and abdominal CT examinations. The acquisition rate in BT-2 was higher for all examinations. In all examinations except for Triple Rule-Out CT, the scan length (SL) data for men was significantly longer (p < 0.001). In brain CT and neck CT examinations, the DLP values were found to be significantly higher in male patients, whereas in abdominal CT, calcium scoring examinations, and high-pitch coronary CT angiography (CCTA), the DLP values were significantly higher in female patients (p<0.001). For brain CT examinations, our medyan CTDIvol value was 53 mGy and the DLP value was 1113 mGy·cm, with the DLP value found to be higher than that of 3 out of 9 compared DRL values, including the national DRL (p < 0.001). For abdominal CT examinations, our medyan CTDIvol value was 17.5 mGy and the DLP value was 909 mGy·cm, with the DLP value again found to be higher than that of 3 DRLs (p < 0.001). For retrospective ECG-gated coronary CT angiography, CTDIvol was 57.4 mGy and DLP was 940 mGy·cm, and our values were significantly higher than the France 2015 DRL (p < 0.001). No significant dose excess was observed in thorax CT, neck CT, calcium scoring, and high-pitch ECG-gated coronary CT angiography examinations. Conclusion:Although the use of DRLs has various limitations, they have become an important part of the dose optimization process. In this study, our data, when compared with DRL values, indicated a need for protocol optimization in brain CT, abdomen CT, and retrospective ECG-gated coronary CT angiography examinations. Furthermore, our success in dose control was demonstrated in thorax CT, neck CT, and prospective ECG-gated coronary CT angiography examinations. Dose optimization is a process that continues as examinations are performed, and our work in this area should continue. Key Words:Computerized tomography, X Ray,Radiation dosage, diagnostic reference levels