Introduction: One of the most common applications of medical isotopes is in treatment of cancer and hyperthyroidism using Iodine-131. The Iodine-131 cumulates in cancerous cells and acts as a source of radioactive emissions. Apparently, local and temporal distributions of the radioactive material are different in various organs. In this paper, the effect of radioactive Iodine distribution on the amount of exposure at different distances has been investigated.
 
Materials & Methods: This analysis has been carried out using adult NCAT phantoms, Monte-Carlo simulation, and GATE code. By applying the same amount of activity on five different organs of the phantom, the quality and quantity of energy has been computed as well as the amount of emitted exposures at distances of one, two, and three meters. Then, by setting thyroid as the basis, the difference of exposure emitted from other four organs has been calculated and analyzed using KS test.
 
Findings: Simulation results had been showed that the amounts of exposure that emitted from aforementioned organs are significantly different at the distance of one meter whereas this difference diminishes significantly at distances of two and three meters. In other words, the effect of radioactive Iodine integration location on the emitted exposure is being trivial as the distance increases.
 
Discussion & Conclusions: Distinct TEDE values must be defined for each of the aforementioned organs and confirmed before releasing patients who will be faced to the others at short distances. Otherwise, guidelines must be considered for the others who will be faced to the released patient.