Résumé :
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The Golden Retriever Muscular Dystrophy dog lacks dystrophin and shares pathological and clinical similarities with the Duchenne patients. The model, increasingly used in pre-clinical trials, needs to be further characterized. We defined NMR imaging indices of canine dystrophic muscle. Six two-month old control and 6 GRMD dogs were examined at 4 T. Three control and 5 GRMD dogs were examined at 3 T at the age of 2, 4 and 6 months. Standard and fat-saturated T1-weighted images were acquired, followed by T2-weighted images. After Gd-DTPA injection, the time-course of muscle enhancement was monitored with fat-saturated T1-weighted imaging during 2 hours. Extensor carpi radialis and flexor carpi ulnaris were studied. Indices were calculated as follows: T2w/T1w signal ratio (SR= T2w Signal x T1w ref gain)/ T1w Signal x T2w ref gain), T1w and T2w heterogeneity (H=?(SD2- SD2noise/0,655) ). An exponential decay was fitted to the signal decrease post Gd-DTPA injection; maximal relative enhancement (RE) and time-constant of decay were compared. A three-way analysis of variance was performed. T2w/T1w SR, H2 and RE were found significantly increased in dystrophic muscles at 4 T. These findings were confirmed at 3 T, at all ages. H1 was also found significantly increased in dystrophic muscle at 4 and 6 months at 3 T. These quantitative indices differentiate dystrophic from normal muscles and might be proposed as non-invasive evaluation tools of therapeutic trials.
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