Figure 3

DSI tractography of a normal rat heart ex-vivo showing the transmural variation in myofiber helix angle: The left ventricle is being viewed (A and C-F) from its lateral wall, and (B) in its short axis. Only those fibers intersecting a spherical region-of-interest are displayed in (D-F). Subendocardial fibers have a positive or right-handed helix angle and in the lateral wall course towards the antero-apex, while those in the subepicardium have a negative or left-handed helix angle and in the lateral wall course from the antero-base towards the postero-apex. Myofiber helix angle transitions smoothly from the subendocardium to subepicardium. Fibers in the mid-myocardium have a zero helix angle and are thus circumferential. Reproduced with permission from Sosnovik et al [27].