Proton-density fat-saturated non-contrast MR imaging is comparable to post-contrast MR imaging for revealing wrist synovitis

Abstract Objectives Standard MR imaging (MRI) for rheumatoid arthritis (RA) patients comprises a post-contrast T1-fat-saturated (T1FS + C) sequence to detect wrist synovitis and tenosynovitis. This study investigates whether non-contrast sequences can provide similar information to post-contrast imaging. Materials and methods Seventy-seven RA patients (F/M: 64/13; age: 61 ± 12 years) underwent MRI examination of the most symptomatic wrist on a 3.0-T system. Axial T1FS + C as well as proton-density imaging with fat-saturation (PDFS) and T2-weighted imaging with fat-saturation (T2FS) sequences were performed. Two radiologists independently scored synovitis and tenosynovitis severity on all sequences, using the rheumatoid arthritis magnetic resonance imaging scoring system (RAMRIS). Intra- and interclass correlation coefficients (ICCs) were assessed. Results For synovitis severity scoring, PDFS was practically identical to T1FS + C, while T2FS overestimated synovitis severity by up to 19%. For synovitis severity, PDFS imaging correlated better with T1FS + C than T2FS imaging (ICC: Reader 1: 0.931 vs 0.897; Reader 2: 0.969 vs 0.948). For tenosynovitis severity, PDFS and T2FS both yielded higher tenosynovitis scores than T1FS + C ( p < 0.001). Compared to T1FS + C imaging, PDFS overestimated tenosynovitis severity by up to 39%, while T2FS overestimated tenosynovitis severity by up to 54%. For tenosynovitis severity, PDFS imaging correlated better with T1FS + C than T2FS imaging (ICC: Reader 1: 0.856 vs 0.731; Reader 2: 0.808 vs 0.800). Conclusion PDFS imaging had good (for tenosynovitis) to excellent (for synovitis) intra- and inter-reader reliability and provides comparable scoring to T1FS + C imaging when evaluating synovitis severity, though it tends to overestimate tenosynovitis severity. PDFS imaging can reasonably replace contrast-enhanced imaging for assessing wrist synovitis in RA patients. Key Points Question Post-contrast imaging is recommended for evaluating synovitis and tenosynovitis in rheumatoid arthritis (RA) patients, though it involves higher cost, scan time, and discomfort. Findings Proton-density imaging with fat-saturation (PDFS) imaging had good to excellent intra- and inter-reader reliability for evaluating synovitis and tenosynovitis in RA wrists. Compared to post-contrast T1-fat-saturated (T1FS + C) imaging, PDFS imaging provides comparable semi-quantitative synovitis severity grading but tends to overestimate tenosynovitis severity. Critical relevance statement Post-contrast imaging for synovitis and tenosynovitis in RA patients involves discomfort, a longer time, and cost. PDFS imaging has good reliability and compares well with post-contrast imaging. In RA wrists, compared to T1FS+C imaging, PDFS imaging provides comparative semi-quantitative synovitis severity grading but tends to overestimate tenosynovitis severity.