Dosimetry

The radiation absorbed dose about 100 Gy leads to a synovectomy similar to surgical synovectomy [2,3]. 

According to the MIRD scheme the estimated reported absorbed dose for Erbium-169 to finger joints is 132.3+/-34.3 Gy, and the synovia (at 40% leakage) is of 73.10+/-25.25 Gy. The reported whole body absorbed dose evaluated in 7 patients is 0.4±0.3 cGy, the estimated blood dose 15 +/- 29 microGy and to lymph nodes 2.3 Gy [4,5]. 

The absorbed dose calculated at the injected joints of the shoulder with Rhenium-186 is 120.5+/-32.2 Gy, hand 130.0+/-12.6 Gy, elbow 83.6+/-38.7 Gy, and talar/subtalar joint 84.1+/-30.7 Gy. The reduced doses to the synovia (at 40% leakage) were for [¹⁸⁶Re]Rhenium-sulphide 65.40+/-32.55 Gy The mean radiation absorbed dose of [¹⁸⁶Re]Rhenium-sulphide to the whole body is 5.3+/-2.7 cGy, liver 10.0+/-8.1 cGy, spleen 20.3+/-22.9 cGy, kidneys 9.4+/-11.4 cGy [4]. 

After intra-articular administration of 185 MBq of Yttrium-90, the MIRD system can be used to calculate an absorbed dose of 92 Gy for a 100 gram spherical volume. The radiation dose caused by 1% leakage from the knee joint after administration of 185 MBq of Yttrium-90 can lead to 10 Gy in the lymph nodes. The joint knee joint absorbed dose evaluated in 6 patients was 130.1 Gy. The reduced doses to the synovia (at 40% leakage) was 59.25+/-46.45 Gy. The whole body dose reported was 15.5 cGy, liver dose 26.5 cGy, splenic dose 11.9 cGy, kidney dose 67 cGy [4]. 

The ambient dose-equivalent rate due to the presence of pure β-emitters in a joint is very low. Assuming that Yttrium-90 causes 1% Bremsstrahlung in tissue, the environmental dose-equivalent rate 1 m away from the knee after the administration of 185 MBq of Yttrium-90 colloid is 0.04 µSv/h.