[Exposure of relatives of patients after stationary radioiodine therapy by inhalation of 131I in their homes].

AIM

From a model of iodine metabolism exhalation coefficients shall become derived to calculate 131I exhalation by patients after a radioiodine treatment. The validity of these exhalation coefficients shall be reviewed by whole body activity measurements of relatives of patients, who inhaled the radioiodine exhaled by the patients in their homes. The exposure of relatives to patients of a nuclear medical ward after release by exhalation of iodine-131 is investigated.

METHODS

Iodine 131I-activity of 17 relatives to patients who had to undergo a radioiodine therapy became measured in a whole body counter only a few days after release of the patient from the nuclear medical ward. The results of the measurements have been compared with the results of calculations according to the model of iodine metabolism.

RESULTS

The calculated values of incorporated radioiodine in the relatives of the patient at time of measurement (Amodel) correlate with the measured whole body activity (AGK) according to the regression: Amodel = AGK -47.3 (r2 = 0.959). This relation holds if 2.1 micrograms of iodine become exhaled per day of the 60 micrograms of iodine which are the daily intake of iodine by food. The exposure of all relatives did never exceed 100 microSveff. Using the same model parameters the effective dose equivalent of the relatives to our patients rises up to 6.5 mSv under ambulant radio therapy condition.

CONCLUSION

The daily exhalation of 131I is able to be calculated by a mathematical model of iodine metabolism. After staying of patients at least 3 days in a nuclearmedical ward the exposure of relatives of patients in their home does not exceed the value of 100 microSveff by inhalation of iodine-131. This are 10% of the limit of 1 mSveff according to the Recommendations of the Commission on Radiological Protection (ICRP 60). Radioiodine therapy outside of a hospital and "iodine therapy tourisme" of German patients to other countries cannot be accepted.