Résumé :
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Communication n° 287. Introduction : Magnetic resonance imaging (MRI) has been used to study in vivo anatomy and water content of dystrophin-deficient skeletal muscle in the murine model (mdx) of Duchenne Muscular Dystrophy. Data are however lacking on the relationships between MRI parameters and muscle histopathological aspects. Objectives : To compare dystrophic and normal muscle by MRI-Texture Analysis (MRI-TA). To explore correlations between histopathology and MRI-TA features. Subjects and Methods: Mdx (n=8) and BL10 control (n=8) mice were used. TA was performed on T2 maps calculated from a multi-echo sequence acquired with a 7T MRI system. TA features from histogram, co-occurrence and runlength matrix methods were extracted from manually drawn regions of interest in 4 calf muscles. In histologic sections of the flexor digitorum superficialis (fds), gastrocnemius caput laterale (gla), and mediale (gme), and soleus muscles, morphometry was used to quantify myofiber size, and the extent of endomysial fibrosis, necrotic and regenerative foci. Correlations were calculated between discriminating MRI-TA features and histomorphometric parameters in each muscle. Results : 10 TA parameters which discriminate between mdx and BL10 mice with an accuracy of 91% were selected. In control mice, MRI-TA parameters correlated with the standard deviation of myofiber lesser diameter (fds and soleus muscles). In mdx mice, histomorphometry demonstrated myofiber atrophy, endomysial fibrosis, and an increased proportion of oxidative myofibers. Necrosis was grouped in 27-631µm diameter foci (1 to 44% of the total muscle area). Regeneration occurred in foci of 25-204µm in diameter (0 to 17% of the total muscle area). In mdx mice, the MRI-TA parameter S(1,0)SumAverage correlated with the mean size of necrotic foci and the mean size of regeneration foci (soleus); distinct MRI-TA parameters correlated with the extent of endomysial fibrosis (gme). Conclusion : MRI-TA allows an in vivo discrimination between mdx and control mice, which correlates with histomorphometric parameters such as necrosis and regeneration extent. MRI-TA would be a promising tool for in vivo monitoring of therapy to muscular dystrophies.
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