comparison of three methods of calculation, experimental and monte carlo simulation in investigation of organ doses (thyroid, sternum, cervical vertebra) in radioiodine therapy

introduction: radioiodine therapy is an effective method for treating thyroid cancer carcinoma, but it has some affects on normal tissues, hence dosimetry of vital organs are important to weigh the risks and benefits of this method. the aim of this study is to measure the absorbed doses of important organs by mcnp (monte carlo n particle) simulation and comparing the results of different methods of dosimetry by performing t-paired test. methods: to calculate the absorbed dose of thyroid, sternum and cervical vertebra using mcnp code, *f8 tally was used. organs were simulated by using a neck phantom and mird (medical internal radiation dosimetry) method. finally, the results of mcnp, mird and tld measurements were compared by spss software. results: the absorbed dose obtained by monte carlo simulations for 100, 150 and 175 mci administered 131 i was found to be 388.0, 427.9 and  444.8 cgy for thyroid, 208.7, 230.1 and 239.3 cgy for sternum and 272.1, 299.9 and 312.1 cgy for cervical vertebra. the results of paired t-test was 0.24 for comparing tld dosimetry and mird calculation, 0.80 for mcnp simulation and mird, and 0.19 for tld and mcnp. conclusions: the results showed no significant differences among three methods of monte carlo simulations, mird calculation and direct experimental dosimetry using tld.