Dose Reduction to the Thyroid Gland in Pediatric Chest Radiography

Abstract

Background It is remain a main concern that pediatric chest radiographies contribute to the significant radiation exposure to the thyroid gland as a more susceptible organ to radiation induced cancer. The aim of this study was to assessment the entrance surface dose (ESD) of pediatric chest radiography compared to the diagnostic reference levels (DRL) and evaluation the efficacy of the lead (Pb) shield in radiation dose reduction to the thyroid gland. Materials and Methods After assessing each patient against specific inclusion-exclusion criteria, 40 pediatric patients who were undergoing anterior-posterior (AP) projection of the chest x-ray were considered eligible for this study. The ESD of the chest and also ESD of thyroid gland with and without a 1 mm butterfly-shaped lead shield which placed on the thyroid gland were measured using high sensitive thermo luminescent dosimeters (TLD-GR 200). Results The average of ESD for chest radiography was 0.068+ 0.04 mGy (0.021 - 0.232 mGy). The unshielded average thyroid ESD was 0.065+0.053 mGy compared to the shielded average thyroid ESD of 0.001 + 0.034 mGy. The use of Pb-shield produced a statistically significant decrease in the average thyroid dose by about 97% (P< 0.001). Conclusion It seems that the Pb-thyroid shield has potential to reduced radiation dose significantly without compromising image quality. The use of thyroid shield in the AP projection of pediatric chest radiography may be an effective method to reduce patient's radiation risk and its usage should be encouraged. Key Words: chest x-ray, pediatrics, radiation exposure, thyroid gland