Background: Despite significant diagnosis benefits, the usage of ionizing radiation is not risk-free. The aim of this study was to determine the risk of thyroid cancer for children who exposed from brain computed tomography (CT) scan.
Method: In this a cross-sectional study, 90 patients under 20 years of age who underwent brain CT-scan were selected. Parameters such as age, sex, imaging technique, imaging characteristics, and thyroid absorbed dose were considered. We used SPSS software, version 21, at 95% confidence interval to analyze the absorbed dose and risk for each individual.
Results: The mean and standard deviation of absorbed the dose for girls and boys for the spiral technique were 3.954±0.393 and 4.72±0.000 mGy and in sequential technique, they were 2.282±0.461 and 1.985±0.431 mGy, respectively. The mean and standard deviation of the absorbed dose in <5 years age group was 5.65±2.00, 3.03±1.34 in 6 to 10 years, 2.63±0.98 in11 to 15 years, and in 16 to 20 years was 2.57±1.04 mGy (P<0.001). There was a significant negative correlation between the absorbed dose and field dimensions (r = -0.604, P<0.001) and slice thickness (r = -0.777, P<0.001). The mean and standard deviation of Lifetime risk for thyroid cancer induction (×105) in <5 years age group in spiral technique was 158.79±322.50 for female subjects and 16.5±42.90 for male patients, which was significantly more than those of other groups and techniques (P<0.001).
Conclusion: The rate of thyroid absorbed dose during brain CT-scan was found to be noticeable, especially in spiral CT imaging, for female patients < 5 years. Based on our results, it was associated with an increased risk of thyroid cancer in this age group.