Coherence of 18F-labelled fluorodeoxyglucose (18F-FDG) uptake and clinical and histopathological assessment of inflammatory arthritis and use of 18F-FDG positron emission tomography/computed tomography for evaluation of therapeutical intervention. (a) Clinical assessment of experimental arthritis was correlated with 18F-FDG enrichment at days 2, 6, 9, 13, 21, and 35 after arthritis induction (n = 42). (b) Regression analysis of acute inflammation and 18F-FDG uptake evidenced a significant correlation of both parameters. (c) Chronic inflammation also significantly correlated with 18F-FDG signalling. (d) Histopathological scoring of total inflammation as the sum of acute and chronic inflammation showed a significant correlation with 18F-FDG uptake. (e) 18F-FDG uptake as a measure of inflammatory arthritis activity in arthritic mice treated with soluble tumor necrosis factor receptor (sTNFR) (etanercept) is significantly reduced compared with untreated controls in the acute stage of arthritis (**P = 0.009; n = 5 per group). (f) Histopathological assessment of diminished (**P = 0.008) arthritis severity in the same mice coincided with 18F-FDG uptake. % ID/g, percentage of injected dose per gram.