Echo-Planar Cardiac MRI using Parallel Imaging

Since it’s original proposal by Mansfield et al. in 1977 [1], echo-planar imaging (EPI) has had a key role in the evolution of cardiac MRI. EPI involves the rapid acqusition of k-space data in a raster-like fashion, requiring a fewer number of excitations compared to conventional 2DFT imaging. This is crucial in cardiac imaging as respiratory and cardiac motion places high demands on imaging speed. EPI has been used for a wide array of cardiac applications including the imaging of myocardial function, perfusion, and coronary arteries, and real-time localization. EPI can be used as a single-shot technique or can be used with multiple excitations with a variety of ordering schemes (e.g. sequential, interleaved, center-out, top-down). It can also be used in a ’fly-back’ mode which involves traversing k-space in the same direction during each echo [2]. There are many subtle variations of EPI, each with its own advantages and disadvantages. Limitations of EPI are well-known [3–6] and include: