The value of diffusion-weighted imaging in the diagnosis of active sacroiliitis

INTRODUCTION: The aim of this study was to evaluate the effectiveness of diffusion-weighted imaging (DWI) in the diagnosis of active sacroiliitis.
METHODS: In this prospective study, 66 patients with clinical prediagnosis of active sacroiliitis were evaluated. Four patients who were not suitable for MRI examination were excluded. Twenty subjects with no complaint of low back pain constituted the control group. All of the patients underwent sacroiliac MRI examination performed with a 1.5 Tesla unit using phase array body coil. Before DWI, oblique axial and coronal T1 and T2-weighted TSE followed by STIR sequences were obtained. DWI examinations were obtained on SS-SE EPI sequence through chemical shifting selective fat supression technique. ‘b’ value was chosen as 50, 400 and 800 mm²/sec and total scanning time was 114 seconds. ADC calculations were made from the ADC maps by placing ROI on the active inflammatory regions in case group and on sacrum and iliac bones in control group.
RESULTS: Of the 62 cases, 42 had a radiologic diagnosis of active sacroiliitis, and 20 were regarded as normal. Mean ADC values in 42 patients with active sacroiliitis were significantly higher than control group. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy rate of DWI in the diagnosis of active sacroiliitis were found to be 100 % for all. The cut-off ADC value was 0.94x10-3 mm²/sec for right sacroiliitis and 0.89x10-3 mm²/sec for left sacroiliitis.
DISCUSSION AND CONCLUSION: We believe that DWI and ADC quantification can be used successfully for the early diagnosis and follow-up of active sacroiliitis.