Evaluation of a rapid, multiphase MRE sequence in a heart‐simulating phantom

The aims of this study were to validate stiffness estimates of a phantom undergoing cyclic deformation obtained using a multiphase magnetic resonance elastography (MRE) imaging sequence by comparison with those obtained using a single‐phase MRE sequence and to quantify the stability of the multiphase‐derived stiffness estimates as a function of deformation frequency and imaging parameters. A spherical rubber shell of 10 cm diameter and 1 cm thickness was connected to a computerized flow pump to produce cyclic pressure variations within the phantom. The phantom was imaged at cyclic pressures between 18–72 bpm using single‐phase and multiphase MRE acquisitions. The shear stiffness of the phantom was resolved using a spherical shell wave inversion algorithm. Shear stiffness was averaged over the slice of interest and plotted against pressure within the phantom. A linear correlation was observed between stiffness and pressure. Good correlation (R2 = 0.98) was observed between the stiffness estimates obtained using the standard single‐phase and the multiphase pulse sequences. Stiffness estimates obtained using multiphase MRE were stable when the fraction of the deformation period required for acquisition of a single image was not greater than 42%. The results demonstrate the potential of multiphase MRE technique for imaging dynamic organs, such as the heart. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.