| Objective:To compare magnetic resonance diffusion-weighted imaging and apparent diffusion coefficients of sacroiliac joints(SIJs) in ankylosing spondylitis(AS) patients during active and nonactive stages.Methods:Based on the modified NEW YORK criteria for AS, 26 patients with chronic low back pain were diagnosed AS. CT and MRI were performed all in the patients and was graded. They were divided into two groups as active group(n=19) and chronic group(n=7)by rheumatologist according to BASDAI and laboratory parameters, and controls with normal SIJs(n=8) were included. ADC values of 45 subchondral bone marrow edema lesions(SBMELs) was measured on ADC maps.Results:Mean ADCs were 1.33±0.36×10-3mm2/s over SBMELs, 0.61±0.17×10-3mm2/s at periphery of SBMELs, 0.64±0.28×10-3mm2/s in chronic-nonactive group, and0.61±0.23×10-3mm2/s for controls. AUC under ROC curve is 0.934 and 0.81×10-3mm2/s is the best cutoff value of receiver operating characteristic(ROC).Conclusions:MR-DWI can offers quantitive analysis of the lesions by ADC values. It may be helpful to detect the presence of sacroiliitis, active or chroic. DWI shows high value in detecting active sacroiliitis in patients with AS. ADCs lower than 0.81×10-3mm2/s,obtained at subchondral aspect of SIJs of established AS patients, which this number represents the receiver operating characteristic(ROC) best cutoff value, can be considered as normal without possible inflammation of concern. |
