RESUMO
Using the MIRD formalism, and the Cristy-Eckeman and Segars anthropomorphic representations, the absorbed dose in the thyroid of newborns, was calculated when 123I (iodide) and 99mTc (pertechnetate) are used during the diagnostic procedures. The dose results will allow exploring the dosimetric impact generated by the use of these radiopharmaceutical compounds and the use of two representations. Regardless the radiopharmaceutical compound and the anthropomorphic representation is the thyroid self-dose is the greatest, due to electrons emitted during the 123I and 99mTc radioisotopes. The relative difference in total dose to the newborn thyroid gland using the Cristy-Eckerman and Segars anthropomorphic representations for the compounds 123I(iodide) and 99mTc(pertechnetate) is 1.82%, and 1.33%, respectively. Regardless of the radiopharmaceutical compound, the replacement of Cristy-Eckerman by Segars phantom does not reflect significant changes in the estimated absorbed dose to the newborn thyroid. Regardless of the anthropomorphic representation, the lowest absorbed dose in newborn's thyroid is obtained when using 99mTc (pertechnetate) is used due to the residence times.
