IVIM-DWI In Diagnosis Of Active Sacroiliitis Of Ankylosing Spondylitis

Objective: To evaluate the value of intravoxel incoherent motion diffusion-weighted imaging（IVIM-DWI）in diagnosing active sacroiliitis of Ankylosing Spondylitis（AS）.Methods: Forty-nine patients with AS（from the Department and Outpatient Department of Rheumatology in the Affiliated Hospital of North Sichuan Medical College from May 2016 to February 2017）and twenty-eight healthy volunteers were randomly enrolled in this study.The selected patients were assigned to active stage group（21 patients）and stable stage group（28patients）according to Erythrocyte sedimentation rate（ESR）,C-reactive protein（CRP）,Bath Ankylosing Spondylitis disease activity index（BASDAI）scores.The diffusion coefficient（D）,the pseudo-diffusion coefficient（D*）and the perfusion fraction（f）were measured using a region of interest approach in the diffusion-weighted imaging（FS-T2 WI and b=800s/mm²）,and data were analyzed by ANOVA.The ability of diagnosis was determined by using receiver operator characteristic analysis.Age,ESR,CRP and BASDAI scores were analyzed by Mann-Whitney U.Results:1.There was no significant difference in the age difference between the stable group and the active group（p >0.05）,activity group BASDAI scores,ESR and CRP were higher than the stable group,the difference was statistically significant（p <0.05）.2.IVIM parameters: activity group D,D *,f values were（0.72 ± 0.29）×10^-3mm²/s,（5.79 ± 3.58）×10^-3mm²/s,（13.56 ± 5.46）%,respectively.Stablegroup D,D *,f values were（0.35±0.16）×10^-3mm²/s 、（4.38±2.48）×10^-3mm²/s、（9.68±3.18）%,respectively.The control group D,D *,f values were（0.29 ± 0.08）×10^-3mm²/s,（3.94 ± 2.88）×10^-3mm²/s,（10.38 ± 4.23）%,respectively.The results showed that the difference of D value among the three groups was statistically significant（p <0.05）.There was no significant difference between the stable group and the control group（p >0.05）.Activity group D* value was higher than the stable group,the control group,and the difference was statistically significant（p <0.05）,there was no significant difference of D* value between stable group and control group（p >0.05）.Activity group f value was higher than the stable group,the control group,and the difference was statistically significant（p <0.05）,there was no significant difference of f value between stable group and control group（p >0.05）.3.Compared the area under the ROC curve of the three parameters,the area under curve（AUC）of D value was the largest,and the sensitivity and specificity was the highest.The optimal cut-off values（with respective AUC,sensitivity,specificity）between active group and stable group were D = 0.42× 10-3mm²/s（0.870,83.80%,74.80%）;The optimal cut-off values（with respective AUC,sensitivity,specificity）between active group and control group were D=0.38 ×10^-3mm²/s（0.923,89.20%,85.30%）.Conclusion:IVDI-DWI can effectively and noninvasively reflect the proliferation and microcirculation perfusion of active sacroiliitis in AS,and D value,D * value and f value are conducive to the diagnosis of the activity of AS,and the D value has the best diagnostic efficiency.