Comparison of fat-saturated T2-weighted and contrast-enhanced fat-saturated T1-weighted sequences in MR imaging of sacroiliac joints in diagnosing active sacroiliitis

• Fat saturated T2-weighted sequence is more effective than contrast enhanced fat saturated T1-weighted sequence in detecting active sacroiliitis.
• Contrast administration is necessary in detecting synovitis of sacroiliac joints.
• Contrast administration may not be necessary in diagnosing active sacroiliitis.

ObjectivesTo compare fat-saturated T2-weighted (FST2W) with contrast-enhanced fat-saturated T1-weighted (cFST1W) pulse sequences in magnetic resonance (MR) imaging of sacroiliac joints in diagnosis of active sacroiliitis associated with axial spondyloarthropathies.Materials and methodsMR examinations of 147 adult patients suspected for sacroiliitis were retrospectively analyzed. Signs of active inflammation, bone marrow edema/osteitis, capsulitis, enthesitis, and synovitis were noted both on FST2W and cFST1W images. Diagnosis of active sacroiliitis was made according to the Assessment in SpondyloArthritis international Society (ASAS) definition.ResultsSixty three patients were diagnosed as having active sacroiliitis based on both FST2W images showing bone marrow edema and cFST1W images showing osteitis. All areas with osteitis seen on cFST1W images were also noted as having bone marrow edema on FST2W images while FST2W images revealed 4 additional areas of active bone marrow changes. Qualitative and quantitative analyses also revealed that FST2W images were superior in showing active bone marrow lesions, the hallmark of active sacroiliitis, while cFST1W images helped detecting enthesitis and/or capsulitis and were necessary for detecting synovitis.ConclusionAlthough cFST1W images help detecting enthesitis and/or capsulitis and are necessary for detecting synovitis, FST2W sequence is superior in detecting active bone marrow lesions and therefore more valuable in diagnosing active sacroiliitis associated with axial spondyloarthropathies based on ASAS criteria.