In-Vivo diffusion MRI tractography of mouse hearts. Myofibers passing through a region-of interest placed in the antero-lateral wall are shown. The fibers are color-coded by the helix angle they make with the left ventricle. (A) Normal mouse heart. The characteristic arrangement of myofibers into an array of crossing helices is clearly seen. (B) Mouse exposed to ischemia-reperfusion with severe hypokinesis in it anter-lateral wall. Mean diffusivity (MD), however, has remained < 1.3 x 10-3 mm2/sec and fiber architecture remains reasonably organized. (C) Mouse exposed to ischemia-reperfusion, also presenting with severe hypokinesis of the anterolateral wall. MD in this mouse, however, is < 1.3 x 10-3 mm2/sec and fiber architecture is severely perturbed.