Résumé
ObjectiveTo analyze the value of grey-scale reversed T1-weighted （rT1） MRI in the detection of structural lesions of the sacroiliac joint （SIJ） in patients with axial spondyloarthritis （ax-SpA）. MethodsFifty-two ax-SpA patients who underwent both MRI and CT in our hospital within a week from February 2020 to December 2022 were retrospectively included. Both sacral and iliac side of each SIJ on oblique coronal images were divided into anterior， middle and posterior portion. Two radiologists reviewed independently three groups of MRI including T1-weighted imaging （T1WI）， rT1 and T1WI + rT1 images to evaluate the structural lesions like erosions， sclerosis and joint space changes in each of the 6 regions of the SIJ. One of the radiologist did the evaluation again one month later. CT images were scored for lesions by a third radiologist and served as the reference standard. Intra-class correlation coefficients （ICC） were calculated to test the inter- and intra-reader agreement for the assessment of SIJ lesions. A Friedman test was performed to compare the lesion results of MRI and CT image findings. We examined the diagnostic performance ［accuracy， sensitivity （SE） and specificity］ of different groups of MRI in the detection of lesions by using diagnostic test. A McNemar test was used to compare the differences of three groups of MRI findings. ResultsCT showed erosions in 71 joints， sclerosis in 65 and joint space changes in 53. Good inter-and intra-reader agreements were found in three groups of MRI images for the assessment of lesions， with the best agreement in T1WI + rT1. There were no difference between T1WI + rT1 and CT for the assessment of all lesions， nor between rT1 and CT for the assessment of erosions and joint space changes （P>0.05）. T1WI + rT1 yielded better accuracy and SE than T1WI in detection of all lesions （Accuracy erosions： 90.3% vs 76. 9%； SE erosions： 91.6% vs 76.1%； Accuracy sclerosis： 89.4% vs 80.8%； SE sclerosis： 84.6% vs 73.9%； Accuracy joint space changes： 86.5% vs 73.1%； SE joint space changes： 84.9% vs 60.4%； P<0.05）. rT1 yielded better accuracy and SE than T1WI in detection of erosions and joint space changes （Accuracy erosions： 87.5% vs 76.9%； SE erosions： 88.7% vs 76.1%； Accuracy joint space changes： 85.6% vs 73.1%； SE joint space changes： 83.0% vs 60.4%； P<0.05）. ConclusionsIn the detection of SIJ structural lesions in ax-SpA， rT1 improves the diagnostic performance and T1WI + rT1 is more superior to others.