Objectives: We investigated the localization pattern of a novel imaging agent, 99mTc-labelled glucosamine (ECDG), in a variety of rheumatic conditions.
Materials and methods: Sixteen patients were recruited into the study, with either active rheumatoid arthritis or osteoarthritis. 99mTc-ECDG was prepared in-house and patients received 400 MBq intravenously; thereafter, static images were acquired 15 min, 2 h and 4 h later, using a dual-head Siemens e-cam. Images were interpreted by an experienced physician for (a) accumulation of tracer at sites of known disease; (b) relative activity over time; (c) detection of subclinical disease; (d) detection of unrelated disease; and (e) distribution of tracer at involved joints.
Results: Optimal images were obtained by 2 h after injection in all patients. 99mTc-ECDG accumulated at all clinically known sites of disease. Uptake was most pronounced in the patients with active but untreated disease. Relative tracer activity at involved joints increased with time when compared with activity in the adjoining soft tissue, liver and cardiac blood pool. Focal uptake was seen with local pathology such as supraspinatus tendinitis. Tracer uptake correlated well with disease severity, and insignificant tracer accumulation was evident at sites with no documented disease. Tracer distribution in joints appeared to conform predominantly to the synovium in patients with rheumatoid arthritis, whereas it was articular in patients with degenerative joint disease.
Conclusion: 99mTc-ECDG accumulates at sites of active rheumatic disease and is able to differentiate between synovial and bone uptake. This agent may have a role in the assessment and monitoring of rheumatic conditions.