Itembu Lannes, Terri Watson, Anders Frank.

Radioiodine treatment of thyroid diseases renders the patient radioactive. To minimize the dose to the patients’ relatives and the general public, restrictions are imposed on the behaviour of the patient. At Karolinska University Hospital Huddinge there has recently been a move from general restrictions to patient tailored restrictions taking into account each patients individual situation. The aim of this project is to measure the personal dose equivalents actually received by family members of radioiodine patients following individualized restrictions in order to assure compliance with the current dose constraints. Confirming that individual restrictions work in maintaining the dose at an acceptable level is important not only for the protection of relatives and general public, it may also allow for administered activities up to 800 MBq whilst still treating the patient as an out- patient.

Family members were issued with hospital ID-bands to wear on their wrists for up to four weeks. Each ID- band contained two LiF: Mg, Ti TLDs calibrated to measure air kerma. The TLDs were analysed and a total personal dose equivalent received by the relative was calculated from the measured air kerma values. The results were compared to the dose constraints of 1mSv for children, 3 mSv for adults and 15 mSv for elderly as imposed by The Swedish Radiation Protection Authority. A total number of 30 relatives to 17 patients, (given an average of 364 MBq (max: 800; min 198)), have so far been recruited. Four of the recruited family members (2 adults, 2 children) later changed their minds and did not want to participate in the study. This leaves the number of relatives used for data analysis at 26 individuals (4 children, 12 adults and 10 elderly) with a max age of 81 years and min age of 10 years.

The observed median personal dose equivalent for the three groups were, 0.26 mSv for children (max: 0.29; min 0.22), 0.33 mSv for adult (max: 0.60; min 0.12) and 0.47 mSv for elderly (max: 1.28; min 0.16). This is well below the individual constraints for all groups.

The observed data suggests that the method of individualised restriction used at Huddinge work as desired in keeping the dose to adult and elderly family members at an acceptable level. However the child group consist of only four children all older than 10 years. Children below 10 years are a high risk group and more data are needed from this group in order to draw any general conclusions.