MRI lesions in the sacroiliac joints of patients with spondyloarthritis: an update of definitions and validation by the ASAS MRI working group

Abstract

ObjectivesThe Assessment of SpondyloArthritis international Society (ASAS) MRI working group (WG) was convened to generate a consensus update on standardised definitions for MRI lesions in the sacroiliac joint (SIJ) of patients with spondyloarthritis (SpA), and to conduct preliminary validation.MethodsThe literature pertaining to these MRI lesion definitions was discussed at three meetings of the group. 25 investigators (20 rheumatologists, 5 radiologists) determined which definitions should be retained or required revision, and which required a new definition. Lesion definitions were assessed in a multi-reader validation exercise using 278 MRI scans from the ASAS classification cohort by global assessment (lesion present/absent) and detailed scoring (inflammation and structural). Reliability of detection of lesions was analysed using kappa statistics and the intraclass correlation coefficient (ICC).ResultsNo revisions were made to the current ASAS definition of a positive SIJ MRI or definitions for subchondral inflammation and sclerosis. The following definitions were revised: capsulitis, enthesitis, fat lesion and erosion. New definitions were developed for joint space enhancement, joint space fluid, fat metaplasia in an erosion cavity, ankylosis and bone bud. The most frequently detected structural lesion, erosion, was detected almost as reliably as subchondral inflammation (κappa/ICC:0.61/0.54 and 0.60/0.83) . Fat metaplasia in an erosion cavity and ankylosis were also reliably detected despite their low frequency (κappa/ICC:0.50/0.37 and 0.58/0.97).ConclusionThe ASAS-MRI WG concluded that several definitions required revision and some new definitions were necessary. Multi-reader validation demonstrated substantial reliability for the most frequently detected lesions and comparable reliability between active and structural lesions.

Quantitative DCE-MRI: An Efficient Diagnostic Technique for Evaluating Early Micro-environment Permeability Changes in Ankylosing Spondylitis

“…In 2019, the ASAS-MRI work group came up with new updated de nitions for joint space enhancement.In these guidelines,increased signal on contrast-enhanced images of the joint space of the cartilaginous portion of the SIJ re ected in ammation at the osteochondral interface,as this would be consistent with the understanding of early histopathological feature of AS [14] .Cognizant to this,studies geared on improving techniques for quantitative evaluation of micro-environment permeability of the joint space before edema and in ammation visualized in adjacent bone marrow of SIJ are necessary.Such improved techniques may provide tissue perfusion as important biological parameters and can further help in understanding the origin of early changes associated with AS.…”

“…We evaluated the interobserver variability for quantitative DCE-MRI parameter measurements. Our results indicated good agreements between the two radiologists for the measurements of quantitative DCE-MRI parameters.Because the accuracy of the result is highly depend on ROI delineating, in order to minimize the selection bias,we placed the ROIs in the upper,middle and lower third of the joint space with the maximum transverse level of SIJ on contrast-enhanced images by the reference of increased signal of the joint space,according to the new update of de nitions and validation by the ASAS-MRI work group [14] .However, standardization of strategies for ROI determination should be done in other subsequent in depth studies.…”

Comparative Study of Imaging and Histology of Sacroiliac Joint in Normal Rats Based on IVIM-DWI and DCE-MRI

“…On the IVIM-DWI and DCE-MRI series, an ovoid region of interest (ROI) was placed within the bilateral sacral or iliac bone marrow. The ROI of the joint space was placed at the lower third of the cartilaginous portion of the SIJ [11] and all ROIs were 2-4mm 2 . The bilateral average values were obtained and care was taken to avoid the cortex, venous plexus, ligaments, or any imaging-related artifacts (Figure 1, 2, 3).…”

Common incidental findings on sacroiliac joint MRI in children clinically suspected of juvenile spondyloarthritis

“…In total 540 pediatric patients were included, 267 (51 %) boys and 264 (49 %) girls with a median age of 14,8 and a mean age of 14,4 (range 0, [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]1). 180 consecutive patients were included in every single institution.…”

“…The presence of active lesions of sacroiliitis was recorded and included capsulitis, joint space enhancement, inflammation at the site of erosion, enthesitis and joint space fluid [16]. The presence of structural lesions of sacroiliitis was also recorded and included sclerosis, fat lesion, erosion, ankylosis and non-bridging bone bud [16]. A global diagnostic impression of sacroiliitis (sacroiliitis yes/no) was recorded.…”