Added Advantages of DWI MR Imaging and ADC Mapping in the Diagnosis of Active Sacroiliitis of Axial Seronegative SpA

Aim: To evaluate the effectiveness of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping in diagnosing active sacroiliitis in patients with axial seronegative spondyloarthropathy (SpA). Material and Methods: This prospective study comprised 26 patients with MR imaging detected active sacroiliitis categorised as a case group, and compared them with healthy controls. ADC value measurements were obtained from the sacral and iliac sides of the bilateral S.I. joints in each case and control group. Independent samples t-test, Chi-square test, and ROC curve analysis were used. Result: Twenty-six patients had active sacroiliitis in 45 S.I. joints, unilateral active sacroiliitis was observed in seven patients (26.9%), bilateral symmetrical in three patients (11.5%) and bilateral asymmetrical in 16 patients (61.5%). The mean ADC value was 1.447 ± 0.528 [SD] × 10 –3 mm 2 /s in the right S.I. joint and 1.630 ± 0.441 [SD] × 10 –3 mm 2 /s in the left S.I. joint in active sacroiliitis (case group). The mean ADC value of the right S.I. joint was 0.965 ± 0.123 [SD] × 10 –3 mm 2 /s and the left S.I. joint was 0.967 ± 0.96 [SD] × 10 –3 mm 2 /s in inactive sacroiliitis (control group). A significant difference was observed statistically between the active sacroiliitis and the inactive sacroiliitis with a P < .0005. A cut-off mean ADC value of 1.034 ×10 –3 mm 2 /s was obtained for differentiating active sacroiliitis from inactive sacroiliitis with a sensitivity of 84.6% and specificity of 84.6% from the ROC curve analysis. Conclusion: Diffusion-weighted MRI imaging with ADC value mapping acts as a sensitive diagnostic technique in the detection of active sacroiliitis in axial seronegative spondyloarthropathies and also helps in assessing the treatment response.