Assessment of active and inactive sacroiliitis in axial spondyloarthritis using DCE-MRI and ZOOMit-DWI parameters: A prospective study.

Accurate assessment of sacroiliac joint disease activity is essential in axial spondyloarthritis. We evaluated the safety and diagnostic utility of quantitative and semiquantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters together with ZOOMit-DWI-derived apparent diffusion coefficient (ADC) values for distinguishing active from inactive sacroiliitis. Patients with sacroiliitis confirmed by Assessment of SpondyloArthritis International Society criteria were prospectively enrolled between April 2019 and December 2020 and classified as active (Ankylosing Spondylitis Disease Activity Score-C-reactive protein ≥ 2.1) or inactive (Ankylosing Spondylitis Disease Activity Score-C-reactive protein < 2.1); age- and sex-matched healthy individuals served as controls. Quantitative DCE-MRI parameters (volume transfer constant [Ktrans], rate constant, extravascular extracellular volume fraction [Ve]) and ADCs from bone marrow and synovial regions, along with semiquantitative metrics (initial area under the gadolinium concentration-time curve [iAUC], fraction of enhancing voxels [Fenh], signal enhancement, time to peak), were extracted. Compared with the inactive group, the active group showed higher sacral Ktrans, Ve, and ADC; higher iliac Ktrans and Ve; and higher synovial Ktrans (all P < .05). Semiquantitative sacral iAUC and Fenh, iliac iAUC and Fenh, and synovial iAUC were also significantly elevated in the active group (all P < .05). Multivariable logistic regression identified sacral Ktrans, sacral Fenh, iliac iAUC, and synovial iAUC as independent predictors of activity, yielding areas under the receiver operating characteristic curve of 0.9317, 0.7937, 0.8794, and 0.7124, respectively. These findings suggest that combined quantitative and semiquantitative DCE-MRI parameters provide a noninvasive and accurate basis for predicting sacroiliac joint activity.