dose reduction to the thyroid gland in pediatric chest radiography

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 evaluate 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+ 0.006 mgy (0.021 - 0.232 mgy). the unshielded average thyroid esd was 0.065 + 0.003 mgy compared to the shielded average thyroid esd of 0.001 + 0.0005 mgy. the use of pb-shield produced a statistically significant decrease in the average thyroid dose by about 97% (p< 0.001). conclusion the use of pb-thyroid shield in the ap projection of pediatric chest radiography has potential to reduced radiation dose without compromising image quality.