131I exhalation by patients undergoing therapy of thyroid diseases.

In the departments of nuclear medicine, patients are treated with relatively large activities of (131)I for therapeutic purposes. The applied activities are in the range of 200-10 000 MBq. Consequently, individuals situated in the dwellings of the patients dismissed from the hospital are subjected to an external as well as an internal radioiodine exposition. Internal exposition is due to the inhalation of (131)I exhaled by the patients. In this article, the measurements of radioactivity exhaled by patients with various thyroid diseases, treated with (131)I in the department of Nuclear Medicine of the Radiological Centre in Goettingen and in the Hospital of Nuclear Medicine in Wuerzburg are presented. The measurements of activities exhaled by patients were repeated daily, up to 25 d after the treatment. In addition, the residual activities were monitored by measuring the external dose rates, and by measuring the (131)I activity in the urine of these patients. In some cases, the exhaled radioiodine was separated into three fractions: the elemental, the organically bound and the aerosol-bound iodine fraction. On the basis of the proposed measurements, the doses received by the family members of a discharged patient treated with (131)I were estimated by a model calculation.