Figure 1

MR imaging and measurement of heterogeneity in the mouse. A: Representative MR images of hindlimb muscles in healthy (wild type, WT) and dystrophic (mdx) mice, both at 9 weeks. The signal in WT hindlimb muscles is homogeneously dark and does not change over time. Compared to WT, dystrophic muscles show heterogeneity, identified by unevenly distributed focal hyperintensities (red arrow) that contrast the dark signal characteristic of healthy muscle. B: The image shows consecutive 0.5 mm thick image axial slices from an mdx hindlimb. Such consecutive slices were used to obtain volume (mm³) ratios of focal hyperintensities to homogeneously dark muscle at every time point and to account for possible changes in heterogeneity along the longitudinal axis of the muscles (yellow boxes).