ジョージアにおける胸部CTの全国診断基準線量値の開発

Computed tomography (CT) is an essential diagnostic modality in modern medicine; however, it is associated with relatively high radiation exposure. Optimizing radiation dose while maintaining diagnostic image quality remains a major priority in clinical practice. Diagnostic reference levels (DRLs) are internationally recommended tools for dose optimization, yet national DRLs for chest CT examinations have not previously been established in Georgia. The objective of this study is to assess radiation dose metrics from non-contrast chest CT examinations across medical institutions in Georgia and to establish preliminary national DRLs for adult and pediatric populations based on real-world clinical practice. A nationwide, multicenter observational study was conducted across 27 Georgian medical institutions. Dose data from 136 consecutive patients who underwent non-contrast chest CT examinations between November 2024 and August 2025 were retrospectively analyzed. Both adult and pediatric patients were included. Radiation dose indicators, including CT Dose Index Volume (CTDIvol) and Dose Length Product (DLP), were collected alongside patient anthropometric parameters. Dose distributions were stratified by body mass index (BMI). DRLs were derived using the 75th percentile methodology in accordance with recommendations from the International Commission on Radiological Protection (ICRP). Substantial inter-facility variability in CT radiation dose metrics was observed, reflecting differences in scanner technology, protocol design, and utilization of automatic exposure control (AEC) systems. BMI-stratified analysis enabled the derivation of realistic, country-specific reference values. The calculated 75th percentile values of CTDIvol and DLP served as the basis for defining preliminary national DRLs for non-contrast chest CT examinations in Georgia. This nationwide assessment demonstrates the feasibility and importance of establishing national DRLs for chest CT in Georgia. The proposed DRLs provide a practical framework for radiation dose optimization without compromising diagnostic quality. Adoption of national DRLs is expected to reduce unnecessary radiation exposure, support continuous quality improvement, and enhance patient safety. Future efforts should focus on periodic DRL updates, broader implementation of dose-optimization technologies, and expansion to additional CT examination types.