[Retention and dosage in radiation synovectomy with yttrium-90-silicate colloid]

Investigations on patients and on phantoms were performed to determine the retention and the absorbed dose in radiation synovectomy with 90Y silicate colloid. The electrons of 90Y are totally absorbed within the surrounding tissue and produce bremsstrahlung with a maximum intensity at about 110 keV. After application of 6 mCi 90Y the dose rate of the bremsstrahlung was measured at a distance of 10 cm over 13 knees in a total of 10 patients and was found to range between 0.6 and 1.3 mR/h. During a period of 3 hours up to 3 days after injection practically no removal of the material from the joint was observed. According to approximative calculations the mean dose absorbed in the knee ranged between 3650 and 7300 rad, and the absorbed dose in the synovium between 5500 and 11000 rad.