Histological validation of myocardial microstructure obtained from diffusion tensor magnetic resonance imaging

Diffusion tensor magnetic resonance imaging (MRI) is a possible new means o f elucidating the anatomic structure of the myocardium. It enjoys several a dvantages over traditional histological approaches, including the ability t o rapidly measure fiber organization in isolated, perfused, arrested hearts , thereby avoiding fixation and sectioning of artifacts. However, quantitat ive validation of this MRI method has been lacking. Here, fiber orientation s estimated in the same locations in the same heart using both diffusion te nsor MRI and histology are compared in a total of two perfused rabbit heart s. Fiber orientations were statistically similar for both methods and diffe red on average by 12 degrees at any single location. This is similar to the 10 degrees uncertainty in fiber orientation achieved with histology. In ad dition, imaging studies performed in a total of seven hearts support a leve l of organization beyond the myofiber, the recently described laminar organ ization of the ventricular myocardium.