Background: Patients with thyroid cancer who receive I-131 treatment in radiotherapy centers are considered a source of external dose received by the workers in these centers as well as the family and the population.
Objective: To evaluate the External Dose Rate (EDR) and Retained Body Activity (RBA) as a function of time and distance during administration of I-131, as well as calculate the urinity radioiodine excretion.
Methods: One hundred and fifty patients were recruited and divided into two groups: The ablation Group (A) and the follow-up Group (B) the EDR, RBA and urinity radioiodine excretion were measured using a digital radiation dosimeter.
Results: Equations have been demonstrated to calculate the EDR and the RBA as a function of time (h) at distances of 0.1, 0.5, 1, 2 and 3 m after administration of I-13. Also urinary iodine excretion in 20 patients for each group was measured to find out the excretion of radioiodine into domestic drainage system.
Conclusion: The equations that were established to calculate the EDR as well as the RBA for a period of up to 96 hours after I-131 administration are useful for estimating radiation doses from patients at radiotherapy centers and could help the workers to minimal exposure.