Quantification of 3-D regional myocardial deformation: shape-based analysis of magnetic resonance images

A comprehensive three-dimensional (3-D) shape-based approach for quantifica tion of regional myocardial deformations was evaluated in a canine model (n = 8 dogs) with the use of cine magnetic resonance imaging. The shape of th e endocardial and epicardial surfaces was used to track the 3-D trajectorie s of a dense field of points over the cardiac cycle. The shape-based surfac e displacements are integrated with a continuum biomechanics model incorpor ating myofiber architecture to estimate both cardiac- and fiber-specific en docardial and epicardial strains and shears for 24 left ventricular regions . Whereas radial and circumferential end-systolic strains were fairly unifo rm, there was a significant apex-to-base gradient in longitudinal strain an d radial-longitudinal shear. We also observed transmural epicardial-to-endo cardial gradients in both cardiac- and fiber- specific strains. The increas e in endocardial strain was accompanied by increases in radial-longitudinal shear and radial-fiber shears in the endocardium, supporting previous theo ries of regional myocardial deformation that predict considerable sliding b etween myocardial fibers.