Non-contrast MRI of synovitis in the knee using quantitative DESS.

Abstract

To determine whether synovitis graded by radiologists using hybrid quantitative double-echo in steady-state (qDESS) images can be utilized as a non-contrast approach to assess synovitis in the knee, compared against the reference standard of contrast-enhanced MRI (CE-MRI). Twenty-two knees (11 subjects) with moderate to severe osteoarthritis (OA) were scanned using CE-MRI, qDESS with a high diffusion weighting (qDESS_High), and qDESS with a low diffusion weighting (qDESS_Low). Four radiologists graded the overall impression of synovitis, their diagnostic confidence, and regional grading of synovitis severity at four sites (suprapatellar pouch, intercondylar notch, and medial and lateral peripatellar recesses) in the knee using a 4-point scale. Agreement between CE-MRI and qDESS, inter-rater agreement, and intra-rater agreement were assessed using a linearly weighted Gwet's AC2. Good agreement was seen between CE-MRI and both qDESS_Low (AC2 = 0.74) and qDESS_High (AC2 = 0.66) for the overall impression of synovitis, but both qDESS sequences tended to underestimate the severity of synovitis compared to CE-MRI. Good inter-rater agreement was seen for both qDESS sequences (AC2 = 0.74 for qDESS_Low, AC2 = 0.64 for qDESS_High), and good intra-rater agreement was seen for both sequences as well (qDESS_Low AC2 = 0.78, qDESS_High AC2 = 0.80). Diagnostic confidence was moderate to high for qDESS_Low (mean = 2.36) and slightly less than moderate for qDESS_High (mean = 1.86), compared to mostly high confidence for CE-MRI (mean = 2.73). qDESS shows potential as an alternative MRI technique for assessing the severity of synovitis without the use of a gadolinium-based contrast agent. The use of the quantitative double-echo in steady-state (qDESS) sequence for synovitis assessment does not require the use of a gadolinium-based contrast agent. Preliminary results found that low diffusion-weighted qDESS (qDESS_Low) shows good agreement to contrast-enhanced MRI for characterization of the severity of synovitis, with a relative bias towards underestimation of severity. Preliminary results also found that qDESS_Low shows good inter- and intra-rater agreement for the depiction of synovitis, particularly for readers experienced with the sequence.