Fig. 2.

Method for semiautomated muscle segmentation. The Osirix “growing region of interest” interface uses dynamic thresholding by averaging the 8 voxels immediately surrounding a seed point (red box) selected by the investigator (in bold). The algorithm determines the means and standard deviations of signal intensities of these 9 voxels and then selects all neighboring voxels falling within a standard deviation of the mean (in blue). In principle, tissue types that match the signal intensity of the seed point are segmented while other voxels are excluded.