MRI assessment of sacroiliitis for the diagnosis of axial spondyloarthropathy: comparison of fat-saturated T2, STIR and contrast-enhanced sequences

Objective: To evaluate whether there are significant differences between contrast-enhanced fat-saturated T-1 weighted imaging and non-enhanced fat-suppression imaging for diagnosing sacroiliitis in patients with inflammatory back pain. Methods: 92 patients, consisting of 46 males and 46 females (mean age: 34 years; range: 15-63 years), who met at least 4 out of 5 Assessment in Spondy-loArthritis international Society criteria for inflammatory low back pain were enrolled in this study. All patients underwent MRI consisting of a coronal short tau inversion recovery (STIR) sequence, axial fat-saturated T-2 weighted imaging (T2FS), and coronal and axial contrast-enhanced fat-saturated T-1 weighted imaging (c & a T1CE). Two observers independently reviewed an image set of coronal STIR with axial T2FS, and an image set of c & a T1CE, at separate times. The degree of bone marrow edema and osteitis was evaluated from each image set. A decision for sacroiliitis positivity for each image set was made based on the findings. The presence of additional active inflammatory findings of spondyloarthropathy such as synovitis, enthesitis and capsulitis were also evaluated. Results: Interobserver and intersequence agreement for the degree of bone marrow edema and osteitis were good or excellent in all quadrants. Cohen's kappa coefficients for sacroiliitis positivity between the two observers were 0.978 and 0.956, and Cohen's kappa coefficients between the two image sets for each observer were 0.892 and 0.870, respectively. The intersequence agreement of additional active inflammatory findings was substantial, and the interobserver agreement was almost perfect or substantial. Conclusion: STIR with T2FS image is comparable to T1CE image for diagnosing spondyloarthropathy. T1CE images may have a role in evaluating additional active inflammatory findings of spondyloarthropathy such as synovitis, enthesitis and capsulitis.