MRI Findings of Sacroiliitis in Ankylosing Spondylitis: Roles of MPGR and Delayed Post-contrast T1-weightedImages

ABSTRACT

PURPOSE: For early diagnosis of sacroiliitis in spondyloarthropathy, the MRI findings of sacroiliitis, roles of MPGR (Multiplanar Gradient Recalled Acquisition in Steady State), and delayed post-contrast T1-weighted images were evaluated. MATERIALS AND METHODS: Twenty six patients with seronegative spondyloarthropathy (probable clinical diagnosis of ankylosing spondylitis) were grouped as either less than radiographic grade I (group A) or more than grade II (group B). The MRI findings of both sacroiliac joints were evaluated in every patient, and predominant sites were determined. The two groups were then compared. In 17 patients, the number of enhancing panni seen on early and delayed post-contrast T1-weighted images was counted and compared between the two groups. RESULTS: Panni were found in all cases, and in both groups, predominant patterns of involvement were the lower and iliac aspects of the sacroiliac joints in both groups; in group A, the synovial joints and punctate pannus were predominantly involved, and in group B, the ligamentous joints as well as the synovial joints and linear pannus. In group B, more periarticular fat accumulation than periarticular osteitis was found. For the evaluation of changes in joint space, MPGR images were superior to spin echo images. For the delineation of enhancing pannus less than radiographic grade I, delayed post-contrast images were statistically superior to those which were early post-contrast. CONCLUSION: MRI can detect early sacroiliitic change according to the predominant sites of involvement, and delayed post-contrast images play a role in the diagnosis of early sacroiliitis. MPGR imaging is good for the evaluation of joint space change.