Session Information
Session Type: Abstract Submissions (ACR)
Background/Purpose:
Active muscle disease in patients with idiopathic inflammatory myopathies (IIM) is characterized by prolonged muscle T2 relaxation on MRI. We examined the utility of MR T2 maps, and a method of correcting these maps for varying fat content, as quantitative, semi-automated alternatives to conventional MRI in the evaluation of IIM. MRI measures were also validated against other myositis metrics.
Methods:
Forty-four IIM patients (8 dermatomyositis [DM], 13 polymyositis [PM], 22 juvenile DM, 1 juvenile PM ) underwent MRI of the thighs at 1.5 Tesla and extensive clinical testing, including assessment of Physician Global Activity (PGA), muscle strength by isometric dynamometry (QMT), functional assessment by Childhood Myositis Assessment Scale (CMAS) and Childhood Health Assessment Questionnaire (CHAQ), and the Myositis Damage Index (MDI). Follow-up imaging was also performed 11 months later in 20 patients after therapy. MRI included a Carr-Purcell-Meiboom-Gill sequence and a Dixon-based fat water separation sequence, for generation of T2, fat fraction (FF), and fat-corrected T2 (fc-T2) maps, and Short Tau Inversion Recovery (STIR) and T1 spin echo (SE) sequences for standard visual assessment. Muscle edema and damage were visually scored on STIR and T1 SE images, respectively, using a semi-quantitative rating system that incorporates anatomic extent and severity of findings. T2, fc-T2, and fat fraction (FF) values were tabulated for the thigh muscles of each patient with an automated segmentation algorithm.
Results:
STIR scores correlated significantly with mean T2 and mean fc-T2 values (Spearman rs= 0.65 and 0.61, p< 0.001), while T1 damage scores correlated with mean FF (rs= 0.67, p< 0.001). Baseline mean T2, mean fc-T2, and visual STIR scores correlated significantly with the CMAS (rs = -0.50, -0.36, -0.55, respectively, p<0.05) and CHAQ (rs = 0.46, 0.35, 0.43 respectively, p< 0.05), and with QMT (rs = -0.49, -0.52, -0.48, respectively, p<0.05). MDI muscle damage scores correlated significantly with visual T1 damage scores (rs = 0.72, p<0.001) and mean FF measurements (rs = 0.67, p<0.001). For 20 patients evaluated after a change in therapy, standardized response means for visual STIR, mean fc-T2, and mean T2 scores were -0.52, -0.31, -0.12, respectively. The change in PGA assessment correlated with changes in STIR (rs = 0.74, p<0.01) and mean fc-T2 scores (rs = 0.46, p<0.05). However, changes in STIR scores and mean fc-T2 values were discordant with outcomes, based on 20% improvement in PGA, in 5 and 6 of 20 patients, respectively.
Conclusion:
Semi-automated survey of quantitative thigh muscle T2, FF, and fc-T2 MRI maps have good content validity with visual scoring of clinical MRI. These quantitative MRI measures have good construct validity with other measures of myositis disease activity and damage, particularly muscle measures. While fc-T2 appears to be more responsive than conventional T2, fc-T2 and T2 are less responsive than visual STIR scores. Additionally, both visual and quantitative MR analysis of thigh muscles exhibited limited agreement with global disease improvement after therapy, as reflected by the PGA assessment.
Disclosure:
L. Yao,
None;
A. L. Yip,
None;
S. Mesdaghinia,
None;
A. Shademan,
None;
J. A. Shrader,
None;
A. V. Jansen,
None;
F. W. Miller,
None;
L. G. Rider,
None.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/magnetic-resonance-imaging-mri-assessment-of-inflammatory-myopathy-quantitative-fat-corrected-muscle-t2-and-conventional-t2-measurement-versus-standard-mri-and-clinical-metrics/