Size-Specific Dose Estimate (SSDE) and Age-Based Local Diagnostic Reference Levels (LDRLs) for Pediatric CT Head Examinations
Abstract
Purpose
To evaluate the Size Specific Dose Estimate (SSDE) based on the AAPM report TG-293 for pediatric head CT, and to propose local diagnostic reference levels (LDRLs) in the Canadian province of Nova Scotia.
Methods
The study analyzed 358 routine non-enhanced head CT examinations. Data were retrospectively extracted from PACS; the survey incorporated five scanners in three hospitals, including a dedicated pediatric facility and two regional general hospitals. Patients were grouped as <1, 1–5, 6–10, and 11–15 years old. Most examinations were performed between 2020 and 2023, with some studies dating back to 2016 due to an insufficient number of pediatric cases from general hospitals. The sample size from each scanner included 4–30 patients under 1 year and 13–30 cases in other age groups. The SSDE was calculated using volume CT dose index (CTDIvol), and a conversion factor based on the water-equivalent diameter, derived using methodology from AAPM Report TG-293. Differences between scanners for all dose metrics were assessed using the Kruskal–Wallis test, with p<0.05 denoting statistical significance. A pairwise comparison of scanners was performed. Provincial LDRLs were proposed as the 75th percentile of the pooled dose distributions for each age group.
Results
Differences in all dose metrics between scanners were statistically significant for all age categories, and median dose values from the pediatric hospital were highest in the province for patients <1 year and 1–5 years old. The CTDIvol and SSDE values demonstrated a strong correlation with Pearson correlation coefficient of 0.905. Larger differences between CTDIvol and SSDE were observed in older patient groups. Provincial LDRLs were determined for each age category and expressed as CT dose indices and SSDE.
Conclusion
The proposed LDRLs expressed as SSDE and CT dose indices provide a useful benchmark for optimizing pediatric head CT and improving protocol standardization.