Real-life radiation burden to relatives of patients treated with iodine-131: a study in eight centres in Flanders (Belgium)

In view of the EURATOM 96/29 [1] regulations, a prospective multicentre study was performed to evaluate the present guidelines given to relatives of patients treated with iodine-131 for both thyroid carcinoma and thyrotoxicosis, based on the real-life radiation burden. This study comprised 166 measurements carried out on a group of 94 relatives of 65 patients. All relatives wore a thermoluminescent dosemeter (TLD) on the wrist for 7 days. Sixty-one relatives agreed to wear another TLD for an additional 7 days. TLD were placed on nine patients' bedside tables. The eight participating centres were arbitrarily divided into three groups according to the period of time they advised their patients to sleep separately. Groups I, II and III respectively advised their patients to sleep separately for 0, 7-10 and 14-21 days. The median dose received by in-living relatives of thyroid carcinoma patients during the 14 days following hospital discharge was 281 mu Sv (doses to infinity not calculated); the median dose to infinity received by in-living relatives of ambulatory treated thyrotoxicosis patients was 596 mu Sv, as compared with 802 mu Sv for in-living relatives of hospitalised thyrotoxicosis patients. In general the children of patients received a significantly (P<0.1) lower mean dose than their partners. For thyroid carcinoma patients, only two relatives out of 19 (10%) exceeded the EURATOM 96/29 limit of 1 mSv/year. For thyrotoxic patients, 28% of relatives exceeded the EURATOM 96/29 limit. but none of them were relatives of patients who followed guidelines for 21 days. The results of this study indicate that sleeping separately for 7 days, after a period of hospitalisation of 2-3 days, will usually be sufficient for thyroid carcinoma patients. For thyrotoxicosis patients, up to 21 days of sleeping separately could be necessary in order to strictly abide by EURATOM 96/29. Therefore, the authors propose the implementation of a non-rigid dose constraint for people who "knowingly and willingly" help patients treated with I-131, while still following the ALARA principle.