Thermal signature analysis as a novel method for evaluating inflammatory arthritis activity.
Brenner M, Braun C, Oster M, Gulko PS
North Shore-LIJ Research Institute, United States.
OBJECTIVES: To determine the potential usefulness of a novel thermal imaging technology to evaluate and monitor inflammatory arthritis activity in small joints using rat models, and to determine whether thermal changes can be used to detect pre-clinical stages of synovitis. METHODS: Three different rat strains were studied in a monoarticular model of inflammatory arthritis of the ankle induced with an intra-articular (IA) injection of complete Freund’s adjuvant (CFA), and compared with the contra-lateral ankle injected with normal saline. Arthritis activity and severity scores, ankle diameters, pain related posture scores, and thermal images were obtained at ten different time-points between 0h (before induction) and day 7. The pristane-induced arthritis (PIA) model was used to study pre-clinical synovitis. Thermal images were obtained at each time-point using the TSA ImagIR System and digitally analyzed. RESULTS: Rats developed similar ankle arthritis detected 6h after the IA injection of CFA, which persisted for seven days. All ankle clinical parameters, including arthritis activity and severity scores, significantly correlated with ankle thermal imaging changes in the monoarthritis model (P<0.003). No thermal imaging changes were detected in pre-clinical stages of PIA. However, PIA onset coincided with increased ankle thermal signature. CONCLUSION:Thermal measurements significantly correlated with arthritis activity and severity parameters. This technology was highly sensitive and could directly measure two cardinal signs of inflammation (warmth and edema – based on ankle diameter) in an area (ankle) that is less than half the size of a human interphalangeal joint, suggesting a potential use to monitor drug responses of rheumatoid arthritis in drug trials or clinical practice.