Bone assessment of the sacroiliac joint in ankylosing spondylitis: Comparison between computed tomography and zero echo time MRI

Purpose: To demonstrate the clinical applicability of zero echo time magnetic resonance imaging (ZTE MRI) in bone assessment of the sacroiliac joint in ankylosing spondylitis. Method: Between January 2021 and November 2021, twenty-one ankylosing spondylitis patients underwent clinically indicated MRI including ZTE sequence, in addition, all patients underwent a CT scan covering the sacroiliac joints within 6 months of the MRI examination. The sensitivity, specificity, and accuracy of ZTE MRI were calculated using CT as the reference standard. Cohen's kappa appa tests were applied to assess the agreement of positive imaging findings (including erosions, osteosclerosis, bony cystic changes, and joint space changes) between MRI and CT as well as the inter-reader agreement for the grading of sacroiliitis in AS patients. Results: There was no statistical significance between ZTE MRI and CT in detecting of ankylosing spondylitis(p> 0.05). The consistency of the diagnosis of positive imaging findings between ZTE MRI and CT was moderate to excellent (ranging from 0.611 to 0.889), and the consistency of the scores of positive imaging was good to excellent (ranging from 0.857 to 0.979). Conclusions: ZTE MRI provides "CT-like" contrast for bony changes of the sacroiliac joint in ankylosing spondylitis and could simplify and reduce costs for some AS patients when both MRI and CT are typically required.