Thyroid Absorbed Dose from Brain CT Examinations in Different Age Groups of Pediatric Based on Monte Carlo Simulation

Abstract

Background: This study was designed to assess the thyroid absorbed dose from brain computed tomography (CT) scans across various pediatric age groups, utilizing Monte-Carlo simulation and thermoluminescent dosimeters (TLDs). Methods: We used the Monte Carlo N-particle (MCNP) transport code to model the spiral CT scan of the brain and calculated the average thyroid dose for each pediatric age group. Techniques for variance reduction, such as Time cutoff, Energy cutoff, and Russian roulette, were implemented. Additionally, a cross-sectional study measured the average thyroid absorbed dose in 45 patients under 20 years using TLD dosimetry. The data were analyzed with SPSS software at a 95% confidence interval (CI). Results: The absorbed thyroid dose for an irradiation time of 1 second and 120 mA across the age groups 0 - 5, 6 - 10, 11 - 15, and 16 - 20 years for boys was 4.165 ± 0.028, 3.802 ± 0.036, 3.861 ± 0.031, and 3.021 ± 0.029 mGy, respectively, and for girls, it was 4.185 ± 0.024, 3.852 ± 0.044, 4.052 ± 0.028, and 4.072 ± 0.047 mGy, respectively. For a dose of 110 mAs, the results for boys were 3.711 ± 0.037, 3.660 ± 0.026, 3.251 ± 0.019, and 3.204 ± 0.031 mGy, respectively, and for girls were 3.882 ± 0.040, 3.842 ± 0.032, 3.412 ± 0.026, and 3.619 ± 0.029 mGy, respectively (P < 0.001). Conclusions: Comparing these results with experimental studies indicates the feasibility of using less computationally intensive methods. The thyroid dose received by girls was higher than that for boys, aligning with findings from experimental studies and other research.