Analysis of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using pharmacokinetic modeling (PKM) provides quantitative measures that mirror microvessel integrity and can be used as an objective marker of the level of synovial inflammation. The aim of this study was to investigate the PKM parametersKtrans, kep, andvein a prospective cohort of disease-modifying antirheumatic drug (DMARD)–naive patients with early arthritis, and to validate the results by assessing their correlation with the number of synovial endothelial cells (ECs).Methods.
Forty-seven patients with early arthritis (arthritis duration <1 year, DMARD naive; comprising 14 patients with rheumatoid arthritis, 22 with unclassified arthritis, 6 with spondyloarthritis [SpA], and 5 with other arthritides) were included. At baseline, DCE-MRI was performed on an inflamed knee joint of each patient. These images were used to calculate theKtrans(volume transfer constant between the plasma and extracellular extravascular space [EES]), thekep(transfer constant between the EES and plasma), and theve(fractional volume of the EES). Second, markers of disease activity were collected. Finally, vascularity was evaluated by immunohistochemical analysis of synovial tissue samples obtained from the inflamed knee joints, using antibodies to detect von Willebrand factor (vWF), a marker of ECs.Results.
The 3 PKM parameters differed significantly between diagnostic groups at baseline, with the highestKtransvalue being observed in patients with SpA (median 0.050/minute, interquartile range [IQR] 0.041– 0.069). Furthermore, theKtrans, kep, andvevalues correlated significantly with markers of disease activity. Finally, the PKM parametersKtransandkep, but notve, correlated significantly with synovial expression of vWF (r = 0.647,P= 0.004 forKtrans; r = 0.614,P= 0.007 forkep; r = 0.398,P= 0.102 forve).Conclusion.
These results suggest that theKtrans, kep, andvecan be used to detect synovial inflammation in patients with early arthritis, and these PKM parameters may be helpful in differential diagnosis. This approach may also be useful in translational research analyzing tissue microcirculation and angiogenesis.