IMAGING MYOCARDIAL FIBER ARCHITECTURE IN-VIVO WITH MAGNETIC-RESONANCE

Methods are presented to image the fiber architecture of the human myo cardium in vitro and in vivo. NMR images are obtained of the diffusion anisotropy tensor, indicative of local myofiber orientation. Studies of cardiac necropsy specimens demonstrate classic features of ventricu lar myoarchitecture including the continuous endocardial to epicardial variation of fiber helix angles (angles to the ventricular circumfere ntial direction) of approximately +1.3 to -1.3 radians. Cross-fiber an isotropy is also observed, In the beating heart, NMR diffusion data mu st be corrected for the effects of myocardial deformation during the c ardiac cycle, This correction can be performed using an independent MR I method to map the strain-rate tensor field of the myocardium through time, Combining fiber orientation with local myocardial strain rate, local rates of myocardial fiber shortening may be computed.