Comparison of radiographs and magnetic resonance imaging in the detection of sacroiliitis in patients with ankylosing spondylitis

The role of radiography and magnetic resonance (MR) imaging in the detection of sacroiliitis in patients with ankylosing spondylitis (AS) was compared in this study. Thirty-six sacroiliac joints in 18 patients with AS were examined with radiography and MR scan. MR images were performed with the sequence of the coronal T1 weighted image, T2 weighted image, and T2* weighted image. Images of all patients were graded according to the modified New York criteria. Statistical results showed that significant differences existed between MR imaging and radiography in the detection of sacroiliitis (P < 0.01). MR imaging was superior to plain film radiographs in visualising erosions (P < 0.01). Radiography cannot reveal the cartilage changes and bone marrow oedema, which can only be seen in MR images. In the absence of radiographic changes, MR imaging can provide objective and complementary findings of sacroiliitis in patients with AS. Due to the ability to image cartilage changes and bone marrow oedema directly, MR imaging may be particularly useful in early diagnosis of sacroiliitis. For patients without any changes on sacroiliac joint radiograph, further examination of MR imaging may be advisable.