Thyroid cancer patients treated with high-dose radioactive iodine (3.7-7.4 GBq) are different from other people because after the administration, the radionuclide I-131 is excreted via urine, feces, saliva and breathing, and also via exposure to other patients. Caregivers of the patient may receive higher radiation doses than normal. The purposes of this study were to estimate the total effective dose equivalent from internal and external exposure to caregivers of patients treated with high dose I-131 admitted at Siriraj Hospital, and to compare the estimated dose with the dose constraint of 5 mSv per annum for caregivers. Thirteen caregivers of 13 patients who underwent radioiodine therapy for thyroid cancers following a standard protocol were given specific instructions with regard to radiation safety and were attached to an electronic personal dosimeter and a personal air sampler pump continuously to measure received radiation dose on a daily basis over three days in the hospital. On discharge day, caregivers were asked to perform an in vivo bioassay by the thyroid uptake instrument. The results from the thirteen caregivers were divided into 3 groups. The total effective dose equivalent to caregivers of patients administered 3.7 GBq (n = 1), 5.55 GBq (n = 9), and 7.4 GBq (n = 3) were 0.159 mSv, 0.123 to 0.629 mSv, and 0.631 to 0.718 mSv, respectively. There values were well below 5 mSv per episode as proposed in the IAEA Safety Reports Series No. 63 and the ICRP Publication 103.

Keywords: Total effective dose equivalent, Caregivers, Thyroid carcinoma, Dose constraint