Apparent diffusion coefficients of sacroiliitis in patients with established ankylosing spondylitis.

Aim: To compare apparent diffusion coefficients (ADCs) of sacroiliac joints (SIJs) in ankylosing spondylitis (AS) patients during advanced-active and advanced-nonactive stages.
Materials-Methods: AS patients with chronic-active (n=19), chronic-nonactive (n=6), and controls with normal SIJs (n=8) were included. Mean ADCs through 43 subchondral bone marrow edema lesions (SBMELs) were calculated.
Results: Mean ADCs were 1.60+/-0.32 × 10-3 mm(2)/s over SBMELs, 0.57+/-0.23 × 10-3 mm(2)/s at periphery of SBMELs, 0.57+/-0.24 × 10-3 mm(2)/s in chronic-nonactive group, and 0.61+/-0.19 × 10-3 mm(2)/s for controls.
Conclusion: ADCs lower than 0.69 × 10-3 mm(2)/s, obtained at subchondral aspect of SIJs of established AS patients with chronic changes, which this number represents the receiver operating characteristic (ROC) best cutoff value, can be considered as normal without possible residual inflammation of concern.
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