Establishment of Typical Values and Correlation Analysis of Dose Indices with Scan Parameters in Computed Tomography Simulation at Naresuan University Hospital

Abstract

Backgrounds: The Department of Medical Sciences of Thailand has established national diagnostic reference levels (NDRLs) for computed tomography (CT) examinations to guide radiation dose optimization. However, each hospital should define its own institutional diagnostic levels (typical values) to reflect actual clinical practice.

Objectives: This study aimed to establish typical values for CT simulation at Naresuan University Hospital. In addition, the study sought to analyze the correlations between radiation dose indices and scan parameters together with patient-related factors.

Materials and Methods: Patient data were retrospectively collected between 2021 and 2023. Radiation dose metrics, including the volume CT dose index (CTDI_vol) and dose length product (DLP), were analyzed for four anatomical regions: brain, head and neck, chest, and pelvis. Typical values were calculated as the median of the dose distributions. Correlations between radiation dose and both imaging parameters and patient characteristics were also evaluated.

Results: The median CTDI_vol values for brain, head and neck, chest, and pelvis regions were 41.6, 21.5, 14.8, and 17.8 mGy, respectively. The corresponding median DLP values were 1,279.3, 929.7, 644.2, and 674.8 mGy·cm. Compared with the NDRLs, the CTDI_vol values obtained in this study were lower, whereas the DLP values were higher. Overall, these typical values were generally consistent with previous reports, particularly those involving CT simulators. Among the examined parameters, scan length showed a strong positive correlation with DLP (r > 0.960), whereas patient factors such as age, weight, and height exhibited weak correlations.

Conclusion: The institutional CTDI_vol values derived from this study were lower than the Thai NDRLs, whereas DLP values were higher. but in line with other published findings. These results provide useful benchmarks for local optimization of CT simulator protocols, supporting radiation dose management and patient safety while maintaining adequate image quality for diagnosis and radiotherapy treatment planning.