Diagnostic value of diffusion-weighted MRI for imaging synovitis in pediatric patients with inflammatory conditions of the knee joint
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Diffusion-weighted imaging (DWI) of synovitis has been suggested as a possible non-invasive alternative to contrast-enhanced T1w imaging (ce-T1w). We aimed to study DWI for diagnosing synovitis in the knee joint of pediatric patients, to quantify inter-observer agreement on DWI and ce-T1w and to calculate quantitative measures of synovial diffusivity and conspicuity.
Forty consecutive patients with known or suspected arthritis of the knee (25 girls, median age 12 years) underwent routine 1.5T MRI with ce-T1w and transverse DWI with b values 50 and 800 s/mm2. Mean apparent diffusion coefficient (ADC) values and signal intensity of inflamed synovium, joint effusion and muscle were measured with regions of interest retrospectively. Post-contrast T1w images (diagnostic standard) and diffusion-weighted images at b = 800 s/mm2 with ADC map were separately rated by three independent and blinded readers with different levels of expertise for the presence and degree of synovitis along with the level of diagnostic confidence.
Thirty-one (78%) patients showed at least some synovial contrast enhancement, 17 (43%) children were diagnosed with synovitis on ce-T1w. Ratings by the 1st reader on ce-T1w and on DWI for synovitis showed very good agreement (kappa = 0.90). Inter-observer agreement on DWI ranged from moderate to substantial with kappa values between 0.68 and 0.79 (all P < 0.001). Agreement and diagnostic confidence were generally lower in patients with mild and without synovial enhancement, compared to patients with synovitis. DWI yielded higher signal of inflamed synovium vs. muscle tissue, but lower signal vs. joint effusion, compared to ce-T1w (all P < 0.001).
Diffusion-weighted imaging is a promising, though reader-dependent alternative to contrast-enhanced imaging in patients with arthritis of the knee, based on our preliminary findings. It holds potential for increasing patient safety and comfort.
KeywordsDiffusion-weighted imaging Knee joint Magnetic resonance imaging Pediatric Synovitis
ML conceived, designed and performed the study, and performed imaging analysis and collected imaging data. AS performed imaging analysis and collected imaging data. AHW contributed clinical patient data. TP set up the MR imaging study protocol. HN conceived, designed and performed the study, performed imaging analysis and collected imaging data, and conducted the statistical analysis of study data. All the authors contributed to drafting the manuscript and they revised and approved of the final version of the manuscript. HN serves as the guarantor of the study.
This study was supported by the German Research Foundation (DFG) (No. NE1953/1-1).
Compliance with ethical standards
All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments. Informed consent was obtained from all individual participants in the study and/or their legal guardians for all diagnostic procedures. A waiver was granted by our Institutional Review Board for the retrospective analysis of anonymised imaging data as presented in this study.
Conflict of interest
No financial or nonfinancial benefits have been received or will be received from any party related directly or indirectly to the subject of this article.
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