Diagnostic Performance of Intravoxel Incoherent Motion Imaging in Evaluating Sacroiliitis Activity in Axial Spondyloarthritis: A Meta-Analysis.

Objectives: Axial spondyloarthritis (axSpA) is a chronic inflammatory disease affecting the sacroiliac joints. MRI detects inflammation, but conventional sequences are non-quantitative. Intravoxel incoherent motion (IVIM) imaging quantifies diffusion and perfusion without contrast agents and may address this limitation. We evaluated whether IVIM parameters distinguish active from inactive sacroiliitis and from healthy controls.

Methods: This systematic review and meta-analysis followed PRISMA guidelines. Literature searches in Web of Science, PubMed, Embase, and Scopus identified studies reporting the diagnostic performance of IVIM parameters-Dslow (pure diffusion), Dfast (pseudodiffusion), and perfusion fraction (f)-for sacroiliitis, up to August 2025. Pooled sensitivity, specificity, and area under the curve (AUC) were calculated with a bivariate random-effects model; heterogeneity with I2.

Results: Six studies comprising 541 participants (178 active sacroiliitis, 277 inactive sacroiliitis, 86 healthy controls) were included. Dslow demonstrated the highest accuracy for differentiating active from inactive sacroiliitis (sensitivity: 86.3%, specificity: 88.1%, AUC: 0.93) and from healthy controls (sensitivity: 89.3%, specificity: 96.3%, AUC: 0.98). Diagnostic accuracy declined for distinguishing inactive sacroiliitis from controls (AUC: 0.72). Dfast and f showed lower diagnostic performances.

Conclusion: Clinically, IVIM-especially Dslow-may serve as a non-contrast adjunct for activity stratification and follow-up; confirmation requires prospective multicentre studies with pre-specified thresholds, direct comparisons with apparent diffusion coefficient and dynamic contrast-enhanced MRI, and assessment of management and cost impact.

Advances in knowledge: This is the first study to meta-analyze and systematically review IVIM for SpA activity monitoring. It confirms the potential capability of IVIM-especially Dslow-as a potential imaging biomarker.