Non-contrast diffusion weighted imaging for the assessment of knee synovitis: a comparative study against contrast-enhanced MRI

Abstract

s / Osteoarthritis and Cartilage 22 (2014) S57–S489 S252 446 NON-CONTRAST DIFFUSION WEIGHTED IMAGING FOR THE ASSESSMENT OF KNEE SYNOVITIS: A COMPARATIVE STUDY AGAINST CONTRAST-ENHANCED MRI E.H. Oei yz, E.J. McWalter y, B. Sveinsson y, M.T. Alley y, B.A. Hargreaves y, G.E. Gold y. y Stanford Univ., Stanford, CA; z Erasmus MC, Rotterdam, Netherlands Purpose: Over recent years, attention has turned to the importance of synovitis in osteoarthritis (OA). Synovitis, characterized by thickening of the synovial membrane and joint effusion, is believed to play a significant role in the pathogenesis of OA, and is regarded as a potential target for novel treatment strategies. The current reference standard for imaging of synovitis is contrast enhanced magnetic resonance imaging (CE MRI) which is associated with higher costs, elevated risks, and prolonged scan times compared to non-contrast enhanced MRI exams. A modified version of the novel three-dimensional (3D) double echo steady state (DESS) sequence can be exploited to image synovitis without contrast agents by increasing diffusion weighting and thereby improving contrast between the synovium and the joint fluid. The purpose of this study was to compare DESS with contrast-enhanced MRI for knee synovitis assessment. Methods: Nine individuals with symptomatic inflammatory arthritis of the knee underwent a 3.0T MRI examination. The protocol consisted of routine clinical sequences followed by the modified 3D DESS sequence (sagittal acquisition with axial reformats; matrix 256 256; field of view 16 cm; slice thickness 3 mm; acquisition time 5:00 minutes) acquired with a high diffusion gradient (10 cycles/voxel) and contrastenhanced (CE) T1-weighted imaging (sagittal and axial; matrix 384 256; slice thickness 3 mm; acquisition time 4:30 minutes). DESS and CE MRI images were scored independently and in random order by a blinded musculoskeletal radiologist. The presence and severity of synovitis was graded at 11 joint sites and a whole-joint sum score was calculated according to the recently published semiquantitative scoring system by Guermazi et al. Diagnostic performance statistics were calculated on the site and patient levels andwhole-joint synovitis scores of DESS were correlated with those of CE MRI (reference standard). Results: Compared to CE MRI, DESS showed good to excellent diagnostic performance for the detection of synovitis of any severity (sensitivity, specificity, and agreement of 81, 85, and 83%, respectively, on site level; and 100%, 100%, and 100%, respectively, on patient level) (see Fig. 1 for illustrative example). DESS, however, systematically underestimated synovitis severity compared to CE MRI (74% absolute score agreement analyzed by site). Excellent correlation was found between summed whole-joint synovitis scores of DESS and CE MRI (Pearson’s correlation coefficient 0.87 (p 1⁄4 0.002), intra-class correlation coefficient 0.86 (95%CI 0.49–0.97)) (Fig. 2). Conclusions: Our results suggest that diffusion weighted imaging with a modified 3D double echo steady state (DESS) sequence acquired with high diffusion gradient is a promising MRI technique for the reliable diagnosis and (semiquantitative) grading of knee synovitis without the need for contrast agents. DESS may be a useful sequence to include in MRI protocols for the comprehensive assessment of OA with reduced costs, risks, and scan time compared to contrast enhanced sequences. Fig. 1. Severe degree of synovitis visualized in the paraand suprapatellar, intercondylar, and posterior cruciate ligament regions (arrows) on CE MRI (left) and DESS (right). Fig. 2. Correlation plot of summed whole-joint synovitis scores of DESS vs. CE MRI. 447 QUANTITATIVE T1r, T2 AND T2* MAPPING OF ARTICULAR CARTILAGE CHANGES IN A RAT MODEL OF OSTEOARTHRITIS USING IN VIVO HIGH-RESOLUTION MAGNETIC RESONANCE IMAGING G. Mohan y, G. Melkus y, K. Subburaj y, S. Magnitsky y, A. Dang z, N.E. Lane x, S. Majumdar y. yDept. of Radiology and BioMed. Imaging, Univ. of California, San Francisco, San Francisco, CA; zDept. of Orthopaedic Surgery, Univ. of California, San Francisco, San Francisco, CA; xDept. of Internal Med., Univ. of California at Davis Med. Ctr., Sacramento, Sacramento, CA Purpose:Magnetic resonance imaging (MRI) has become a key imaging tool in osteoarthritis (OA) research due to its ability to visualize bone as well as soft tissues such as cartilage, ligaments, menisci and synovium. Cartilage matrix degradation is a characteristic feature of OA and compositional MRI can assess early biochemical (proteoglycan and collagen content) and structural changes in the cartilage. Quantitative MRI techniques such as T1r, T2 and T2* were shown to provide accurate