Very limited data are available in the literature on the doses of unwanted radiation that patients receive following treatment with radiosynoviorthesis (RSO). Objective: The aim of this study was to assess the radiation exposure after RSO with 186Re colloid in hemophiliacs. Methods: This study involved 12 hemophiliacs who were treated for hemophilic joint disease with 14 RSOs by using 186Re colloid. Whole-body scintigrams were performed 1, 6, and 24 hours and 3 and 7 days after RSO. Measurements, using a whole-body counter, were done immediately after scintigraphy, with the treated joint protected with a lead shield. The cumulative activity of 186Re in the body and in the lymph nodes was calculated. The distribution of 186Re in the body was determined by using the values for small colloids as proposed by the International Commission on Radiological Protection (ICRP) Publication 53. The computer code, OLINDA/EXM (Vanderbilt University, Nashville, TN), was used for the calculation of the internal dose. A constant distance of 1 m between the ankle joint and body organs, and of 0.33 m between the elbow or shoulder joint and body organs, was used to calculate the contribution of gamma radiation to the effective radiation dose. Results: The mean effective dose received by hemophiliacs after RSO with 186Re colloid was 28 ± 9 μSv/MBq of the activity injected into the joint. The patients received 0.8–3.7 mSv (1.9 ± 0.8 mSv) owing to the leakage of 186Re from the treated joint and its retention in the body. The highest doses were established in the spleen (26.0 ± 10.7 mGy), the liver (17.6 ± 7.2 mGy), and red marrow (3.0 ± 0.8 mGy). The contribution of gamma radiation to the effective dose was less than 0.1 mSv in RSO of the ankle, 0.4 mSv in the elbow, and 0.6 mSv in the shoulder-joint treatment. The activity of 186Re in the regional lymph nodes was noted in 4 of the 14 treatments. In these cases, the estimated average dose received by individual lymph nodes was 14.7 ± 1.9 Gy. Conclusions: RSO with 186Re colloid is a safe treatment method. The effective dose received by patients after RSO by using 186Re colloid is low, as are the radiation doses to the most exposed organs. If 186Re is retained in the regional lymph nodes, the lymph node radiation dose would be high.
