Stability of radioactive colloids for radiation synovectomy: influence of X-ray contrast agents, anaesthetics and glucocorticoids in vitro

AIMThis in-vitro study investigated the influence of the contrast agents iothalamate (Conray) and special preparations of iotrolan (Isovist) and iopromide (Ultravist) without ethylenediaminetetraacetic acid (EDTA), the anaesthetic Scandicain and the glucocorticoid triamcinolone on the stability of Y-, Er- and Re-radiocolloids used for radiation synovectomy. METHODSVials of 1 ml of synovial fluid and 0.02 ml of radiocolloid suspension (0.56–3.6 MBq) were mixed with 0.06, 0.6 and 1.0 ml of each contrast agent. In an additional series, 0.1 ml of Scandicain and 0.1 ml of triamcinolone were tested. Thin layer chromatography and ultrafiltration/centrifugation were performed between 1 h and 15 days after incubation with negative and positive controls. RESULTSWithin 24 h, 0.6 and 1.0 ml of Conray had mobilized 5–20% of the Y and Er out of the colloids. No interference between Re-colloids and Conray was visible before the ninth day after incubation. Iotrolan and iopromide without EDTA had no effect on the stability at shorter incubation periods of up to 6 days. The addition of Scandicain did not produce low-molecular Y or Er in the presence of synovial fluid. The fraction of low-molecular Re reached 4% after 24 h. Triamcinolone did not have any effect on stability in the presence of synovial fluid. CONCLUSIONThe disintegration of the radioactive colloids can be attributed to either the formation of EDTA complexes or radiolytic effects. The volume of the injected contrast agent should be as small as possible to confirm correct intra-articular distribution.