Comparative assessment of radiation dose metrics and lifetime cancer risk in chest and abdominopelvic CT imaging

This study aimed to establish regional Diagnostic Reference Levels (DRLs) for chest and abdominopelvic CT examinations in the Madina region of Saudi Arabia, and to conduct a comparative assessment of effective dose (ED) using two methodologies—Monte Carlo–based NCICT simulation and region-specific k-factor conversion. It further sought to derive lifetime attributable cancer risk (LAR) based on ICRP risk models using both ED approaches and to apply the BEIR VII model to evaluate variations in LAR across different ages and between male and female patients. A retrospective multicenter analysis was performed on 420 adult patients scanned across four hospitals using eight CT scanners from four major manufacturers. Patient and exposure data (CTDIvol, DLP, and scan parameters) were collected in accordance with ICRP guidelines. DRLs were defined as the 75th percentile of the dose distributions. ED was estimated using both NCICT and k-factor methods, and LAR was calculated using ICRP and BEIR VII risk models. The proposed DRLs were 10.9 mGy and 394 mGy cm for chest CT, and 12.5 mGy and 638 mGy cm for abdominopelvic CT, consistent with national and international benchmarks. NCICT-derived ED values ranged from 3.8 to 6.3 mSv (chest) and 3.0–8.2 mSv (abdominopelvic), whereas k-factor estimates ranged from 7.2 to 10.5 mSv and 4.7–12.1 mSv, approximately 1.6–1.9 times higher. Corresponding LAR values ranged from 1.9 to 3.1 to 3.5–5.9 per 10,000 scans depending on the model used. The BEIR VII analysis showed higher risks in females and younger patients, with risk declining steadily with age. Significant differences in radiation dose and lifetime cancer risk were observed for chest and abdominopelvic CT scans, influenced by both the estimation methods used and variations in scanning protocols.