Measurement of thyroid absorbed dose in some common medical radiographies on Rando phantom

  Background and Objective : The thyroid gland is one of the critical organs, that has the high sensitivity to radiation and the most important effect of radiation on thyroid is malignancy production, so for this reason this organ is known as a critical organ dose in radiobiology and protection. The main goal of this study was the measurement of thyroid absorbed dose in some common medical radiography.   Material and Methods : this research is a lab- experimental study, which is done on Rando phantom using three phase high frequency diagnostic radiology machine, film speed 400, and high speed intensifying screen and thermo luminescent dosimeters (TLD 100). In this study the TLD chips that were located in small radiolucent sachets were taped on the anterior surface of thyroid. We used special dosimeters for any radiographies separately, and finally the thermo luminescent dosimeters were read out with a Harshaw 3500 TLD reader, and the thyroid absorbed dose calculated in 12 different radiography.   Results: A according to the findings of this study which is carried out for evaluation of thyroid absorbed dose in chest, skull, thoracic spine, lumbar spine, abdomen and pelvis, the thyroid absorbed dose has not been in zero value. The maximum absorbed doses for this critical organ has been 0.68 ±0.03 mGy in thoracic vertebra (AP) and minimum absorbed dose has been 0.12±0.03 mGy in Chest x-ray (PA) respectively.   Conclusion : Based on our findings in this research, it's defined that the thyroid absorbed dose in evaluated radiographies is not zero, even in some cases which the thyroid is very far from the radiation field the scattered radiations will collide with this critical organ. Therefore, for prevention of stochastic effect of radiation on thyroid, we suggest that the radiation protection of thyroid in all radiographic procedures is essential.