Application of DENSE MR-Elastography to the human heart: first in vivo results

Introduction Typically, MR-Elastography (MRE) encodes the propagation of monochromatic acoustic waves in the MR-phase images via sinusoidal gradients characterized by a detection frequency equal to the frequency of the mechanical vibration [1]. Therefore, the echo time of a conventional MRE sequence is typically longer than the vibration period, which is critical for heart tissue exhibiting a short T2*. Thus, fast acquisition techniques like the “so-called” Fractional Encoding of Harmonic Motions (FEHM) were developed for cardiac applications [2]. However, FEHM is limited since it is two orders of magnitude less sensitive to motion than conventional MRE sequences for low frequency vibration. Here, an MRE sequence (Fig. 1) is derived from the “so-called” Displacement Encoding with Stimulated Echoes (DENSE) sequence [3], and it is adapted to in vivo acquisitions of the human heart for two volunteers.