Introduction: Nowadays, radioisotopes have a lot of therapeutic and diagnostic applications in nuclear medicine. The technetium-99m radioisotope is widely used in the diagnostic field. The technetium-99m radioisotope is widely used in the diagnostic field. In this study, in order to increase the absorption dose in thyroid cancer cells, the radioactive drug technetium-99m which is gamma emitter has been used along with iodine precursor in the desired concentrations.
 
Materials and Methods: Using the MIRD method and the MCNP simulation code, the absorbed dose and the effective dose originating from the radioactive technetium-99m, has been calculated for thyroid with the stable iodine contrast in the concentrations of 5, 10 and 100 mg/ml, and without it. Regarding the concentration of stable iodine in the thyroid that increases its equivalent atomic number, when photon is encountered with thyroid cancer cells with high equivalent atomic number, it creates photonelectrons. These photoelectrons can effectively lead to DNA fractures and thus cause damage and kill cancer cells.
Results: Considering the activity of 185 MBq from the radiopharmaceutical technetium-99m and stable iodine contrast in the desired concentrations, the increase percentage of absorption dose in the thyroid in the presence of stable iodine with concentrations of 5, 10 and 100 mg/ml was 7.25, 7.77 and 15.5%, respectively.
Conclusion: The results of this study indicate that prescription of stable iodine contrast in different concentrations along with technetium-99m increases the absorption rate of the thyroid. Therefore, this technique can be used to treat thyroid tumors with technetium-99m which is a gamma-emitting agent.