Unexpected dose to the daughter of a patient treated with iodine-131 for hyperthyroidism

Patients treated with radioiodine for thyrotoxicosis and hyperthyroidism are a source of radiation exposure and represent a potential radiation hazard for the people in their environment. Doses to the relatives can be estimated from dose rates of the patient or measured with a proper dosimeter. Sensitive thermoluminescent dosimeters have been used to measure the doses absorbed by the family members of patients treated with iodine-131 ((131)I) for thyrotoxicosis. In the present case, a 12 year old daughter of a female patient, aged 41 years, treated with 592 MBq of (131)I, received a dose of 7.79 mSv during the first seven days. This value is well above the dose constraints proposed by the International Commission on Radiological Protection, i.e 1 mSv for children and fetuses and 3 mSv for carers. Obviously, the patient and her daughter didn't follow the given restrictions. That was unexpected for a 12 year old child who didn't need special care and was able to understand and follow certain instructions. It is the opinion of the authors that if there are children in the family of a hyperthyroid patient treated with (131)I, they should stay in another house for at least a week. If this is impossible for social reasons, hospitalization of the patient should be considered, although treatment of thyrotoxicosis is held in an out-patient basis.