Abstract: Objective To assess the performance of high-frequency ultrasound in evaluating articular lesions in a rat of model
collagen-induced arthritis model (CIA). Methods Sixty Wistar rats randomized into CIA group (n=50) and the control group
(n=10), and in the former group, CIA was induced by immunization with collagen type II. On day 45, the ankle joint was
assessed based on the arthritic index (AI) and examined with high-frequency ultrasound in all the rats. Histological
evaluations of the joint were performed and the results were compared with ultrasound findings. Results In CIA group, 62
ankles were confirmed pathologically to have synovitis with typical inflammatory cell infiltration and pannus formation. AI
score-based diagnosis was confirmed in 42 ankles with a detection rate of 68% (42/62), significantly lower than the rate of 87%
(54/62) with high-frequency ultrasound (P<0.05). Conclusion High-frequency ultrasound is an ideal method for observing CIA
in rats in vivo. High-frequency ultrasound can show blood flow in rheumatoid arthritis and is useful in studies of RA synovial
angiogenesis.