Diffusion MRI in the heart

Abstract

Diffusion MRI provides unique information on the structure, organization, and integrity of the myocardium without the need for exogenous contrast agents. Diffusion MRI in the heart, however, has proven technically challenging because of the intrinsic non‐rigid deformation during the cardiac cycle, displacement of the myocardium due to respiratory motion, signal inhomogeneity within the thorax, and short transverse relaxation times. Recently developed accelerated diffusion‐weighted MR acquisition sequences combined with advanced post‐processing techniques have improved the accuracy and efficiency of diffusion MRI in the myocardium. In this review, we describe the solutions and approaches that have been developed to enable diffusion MRI of the heart in vivo, including a dual‐gated stimulated echo approach, a velocity‐ (M 1) or an acceleration‐ (M 2) compensated pulsed gradient spin echo approach, and the use of principal component analysis filtering. The structure of the myocardium and the application of these techniques in ischemic heart disease are also briefly reviewed. The advent of clinical MR systems with stronger gradients will likely facilitate the translation of cardiac diffusion MRI into clinical use. The addition of diffusion MRI to the well‐established set of cardiovascular imaging techniques should lead to new and complementary approaches for the diagnosis and evaluation of patients with heart disease. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.

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“…However, in addition to its high system cost, the limited spatial resolution of DTI makes it extremely challenging for revealing detailed myocardial fiber structure in the small mouse hearts. A typical mouse heart has a diameter of ~6 mm with 1~2 mm thick ventricular wall and the myofiber orientation can change over 100° across the thin ventricular wall [6,7]. Abrupt orientation changes of more than 50° were observed between different epicardial layers [7].…”

“…The MRI based diffusion-tensor imaging (DTI) technology is the only practically available tool for imaging myocardial fiber structure in the whole heart [6]. However, in addition to its high system cost, the limited spatial resolution of DTI makes it extremely challenging for revealing detailed myocardial fiber structure in the small mouse hearts.…”

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