查看文章

In MR elastography (MRE) shear waves are magnetically encoded by bipolar gradients that usually oscillate with the same frequency f_v as the mechanical vibration. As a result, both the repetition time (TR) and echo time (TE) of such an MRE sequence are greater than the vibration period 1/f_v. This causes long acquisition times and considerable signal dephasing in tissue with short transverse relaxation times. Here we propose a reverse concept with TR ≤ 1/f_v which we call “fractional” MRE, i.e., only a fraction of one vibration cycle per TR, can be used for motion sensitization. The benefit of fractional MRE is twofold: 1) acquisition times in seconds can be achieved for a single‐phase difference wave image, and 2) materials that combine low elasticity, high viscosity, and short T relaxation times show an increased phase‐to‐noise ratio (PNR). A twofold increase of the phase signal is predicted for liver‐like materials …