Integration of Muscle Fat Fraction and Apparent Diffusion Coefficient Analyses to Track Disease Progression in Oculopharyngeal Muscular Dystrophy Using Whole-body Quantitative MRI
Tanay Satarkar1, Ian Smith3, Gerd Melkus3, Marcos Sampaio3, Fadi Esttaifo2, Kaitlynn Meier-Ross2, Sono Khan2, Jodi Warman4
1Graduate student, University of Ottawa, 2University of Ottawa, 3Ottawa hospital research institute, 4The Ottawa Hospital
Objective:
To evaluate 97 muscles cross-sectionally and longitudinally, quantify fat fraction (FF), and test whether diffusion related MRI markers like Apparent Diffusion Coefficient (ADC) precede or correlate with fat infiltration.
Background:
Oculopharyngeal muscular dystrophy (OPMD) a slowly progressive disorder marked by ptosis, dysphagia, and proximal weakness. Quantitative MRI (qMRI) is an emerging biomarker that may support severity assessment and monitoring.
Design/Methods:
We studied 31 patients with OPMD and 10 controls. All underwent whole body 3T qMRI with two-point Dixon for FF, ADC for diffusivity . Seven patients had follow-up scans after 22.7 ± 4.1 months. We segmented 97 muscles for FF and ADC, using ITK SNAP 3.8.0. Analyses used Prism and R using Wilcoxon, Mann Whitney tests and Pearson or Spearman correlations, p<0.05.
Results:
Adductor Magnus (AM) Soleus (SO), Biceps Femoris (BL), Semi Membranous (SM), Tibialis Posterior (TP) showed higher FF, and FF increased with age (<55 y 17%, 55–65 y 34.9%, >65 y 54.3%) and disease duration. Within muscles (AM, BL, SM, SO), higher FF was linked to a negative correlation between FF and ADC (spearman rho=-0.55, p value =<0.05). Muscles (AL, TP, AM, Serratus Anterior, SM) showed significant within subject FF increases (range= +2.1 to +5.7 % absolute change). Muscles with higher mean FF and wider between patient ranges of FF and ADC have a stronger negative (FF-ADC Pearson correlation co-efficient R²=0.49, 0.59, 0.30). Baseline ADC did not predict later FF change (Spearman rho range: -0.35 to +0.30 p value>0.05).
Conclusions:
FF is sensitive marker of progression and shows a robust within-muscle negative relationship with ADC. ADC is poor standalone marker and does not predict future FF change in this cohort. Future analysis would aim to provide muscle-specific context (e.g., mean-or control-subtracted ADC), assess the presence of edema and increase the sample size to potentially enhance ADC’s effectiveness in monitoring OPMD.
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