Abstract

• Radioisotopes are widely used to diagnose disease and as effective treatment tools. Since many years radioactive iodine 131I has been used to treat thyroid disease. The external measurements of dose rate (µSv/hr) of thyroid cancer patients for various distances are obtained at Department of Nuclear Medicine in Yangon General Hospital. These results are satisfied the inverse square law. From these results the maximum permissible exposure time for various distances from thyroid cancer patients are calculated. It is found that the maximum permissible exposure time is the longest time for the people that stay away from the patients after giving iodine treatment. Finally, it is concluded the further from the patients treated iodine, the longer the maximum permissible exposure times.