Assessment of myocardial structure and function using magnetic resonance imaging

Cardiovascular disease is the leading cause of death in the United States. Cardiovascular magnetic resonance imaging (MRI) has grown over the last twenty years into a leading diagnostic clinical technique for the assessment of cardiovascular function and disease. The applications of cardiovascular MRI range from basic science to clinical and include in vivo and ex vivo work. This work describes recent developments in cardiovascular MRI that are useful for characterizing the structure and function of the myocardium.; Regional myocardial function can be quantified using tagged MR imaging. In this work previous limitations of tagged MR are overcome and the resulting methods are applied to studies in patients and canines. In one study a series of patients with familial hypertrophic cardiomyopathy (FHC), a genetic disease which causes excessive thickening of the heart muscle, were imaged using tagged MRI to quantify dysfunction during all phase of the cardiac cycle. Marked differences were found during diastole, a period of the cardiac cycle that was previously difficult to image.; In another series of experiments the development of an improved resolution tagged MRI protocol provided the ability to characterize transmural strains and the full three dimensional strain tensor. Previous implementations of tagged MR imaging were limited to one or two tags across the transmural extent of the left ventricular myocardium. The low number of transmural tags precludes the analysis of radial thickening strains and radial-circumferential shear strains, hence the three dimensional strain tensor could not be fully measured. The new tagged MR imaging technique reveals a gradient in radial thickening that increases from sub-epicardium to sub-endocardium.; The use of diffusion tensor MRI (DTMRI) for quantifying the complex myofiber arrangement in the ex vivo heart is evolving as the new "gold standard." The datasets include millions of estimates of the local diffusion tensor each of which contains information about the local myofiber orientation and other structural details, which are extracted using eigensystem analysis. The use of superquadric functions is demonstrated as an intuitive technique for visualizing the tensor data. This technique is applied to canine myocardium to reveal previously unreported structural details.