[Environmental radiation exposure of a thyroid cancer patient resulting from adjuvant iodine radiotherapy].
The aim of the study was to evaluate radiation risk in the environment of patients treated with 131I as an ablative therapy following radical surgery for the differentiated thyroid cancer. The activities of radioiodine used in this form of therapy approximate 2.8 GBq (76 mCi) and the in cases of the cancer metastases to other organs may be as high as 7.4 GBq (200 mCi). Dose equivalent rates were estimated in nine seated patients at the level of the thyroid close to the gland surface, and 0.5 and 1 m away from it. The measurements were performed at one, 24, 48, 72, 96, 120, 144, and 168 hours after the injection of 131I. The dose equivalent rates at various distances from the thyroid surface at different times were approximated with the exponential function by the least square method. Then, the dose equivalents were calculated from the moment of 131I application to the moment of the total removal of the isotope from the organism. From this relation, time intervals after which the annual threshold doses of 1, 5, and 50 mSv would be exceeded were computed as the function of the applied 131I activity. The results of the present study indicate that attendants of the patients treated with 131I will not be exposed to the doses of ionising radiation exceeding the acceptable annual thresholds provided with the limited time intervals. In addition, the present results may be useful in elaborating procedures of dealing with and handling the patients during their stay at hospital, at home, and at work.