Development of Diagnostic Techniques for Early Rheumatoid Arthritis Using Positron Emission Tomography with [ 11 C]PK11195 and [ 11 C]Ketoprofen Tracers.

PURPOSE: In vivo detection of pathological insults during the early stages of rheumatoid synovitis is essential to allow early anti-inflammatory treatment for prevention of joint destruction. Whether rheumatoid synovitis pathology and the efficacy of therapies can be visualized by positron emission tomography (PET) tracers specific to the inflammatory process was investigated.

PROCEDURES: Using a collagen-induced experimental rat model of rheumatoid arthritis, in vivo imaging using the PET tracers [11 C]PK11195, which binds to the translocator protein mainly expressed on myeloid cells, and [11 C]ketoprofen, for cyclooxygenase imaging, was performed. To evaluate therapeutic efficacy, model animals were administered the tumour necrosis factor alpha blocker etanercept subcutaneously.

RESULTS: [11 C]PK11195 and [11 C]ketoprofen uptakes were significantly higher in inflamed paws of collagen-induced arthritis rats than in normal rats. The data showed a correlation between tracer uptake values and paw swelling. After treatment with etanercept, [11 C]ketoprofen uptake was significantly lower in treated animals than in untreated ones, whereas [11 C]PK11195 uptake in the inflamed regions was comparable to that in the untreated group.

CONCLUSIONS: With [11 C]PK11195 and [11 C]ketoprofen tracers, non-invasive in vivo PET imaging for rheumatoid synovitis can provide diagnostic evidence of early synovitis and allow monitoring inflammatory cell activity during treatment.