Noninvasive stiffness imaging techniques (elastography) can image myocardial tissue biomechanics in vivo. However, for cardiac magnetic resonance elastography (MRE) techniques the optimal vibration frequency for in vivo experiments is unknown. Since the myocardium is thinner than typical MRE shear wavelengths, waveguide effects dominate the wave propagation, and incorrect stiffness estimates will result if these are not accounted for. In principle, taking the curl of the displacement field (1) will help reduce boundary affects, but at the expense of noise amplification. Higher vibrational frequencies imply higher resolution, but these attenuate quickly. Lower frequencies penetrate deeper, but have stronger waveguide effects, and smaller spatial derivatives with less tolerance to noise. The purpose of this study was to determine the optimal vibration frequency for cardiac MRE in healthy volunteers.3D cardiac MRE was performed on 8 healthy volunteers. Vibration was delivered to the heart with a passive drum driver (Figure 1A) in direct contact with the volunteer’s skin, just to the left of the sternum and superior to the xiphoid process (Figure 1B). To establish a “no-motion” baseline measurement of noise, a full MRE exam without the application of any vibrational motion was performed on one volunteer. Cardiac gating was performed by placing electrocardiography leads on the back of the left shoulder of the volunteers. Volunteers were imaged head first in the supine position. Imaging was performed on a 1.5-Tesla closed-bore MR imager (Optima MR450W; GE Healthcare, Milwaukee, WI, USA) in an oblique orientation to obtain long-axis MRE images of the heart. Imaging was conducted using a flow-compensated, cardiac-gated, spin-echo, single-shot echo planar imaging MRE sequence, with vibration frequencies of 80Hz, 100Hz, 140Hz, 180Hz and 220Hz; TR was matched to each volunteer’s heart rate with electrocardiogram-gating, TE = 52-79ms depending on frequency; FOV = 32 cm; 64x64 acquisition matrix; parallel imaging acceleration factor = 2; 5 contiguous 5-mm-thick axial slices; 1-2 motion-encoding gradient pairs; alternating x, y, z, and 0 motion-encoding gradient directions; and 4 phase offsets. The left ventricle of the heart was semi-automatically segmented and the octahedral shear strain signal-to-noise ratio (OSS-SNR) (2) was calculated on the curl wave fields.The out of plane component of the vector curl field, the corresponding elastograms (magnitude of complex shear modulus |G*|), and a map of the voxels with OSS-SNR > 1.6 on the curl data are shown in Figure 2 for a single volunteer over the 80-220 Hz frequency sweep. The mean OSS-SNR (Figure 3A) and the percentage of voxels with OSS-SNR > 1.6 (Figure 3B) over the entire myocardial volume were calculated for each volunteer at each vibration frequency. The percentage of voxels that remain in the “no-motion” and “motion” data sets as a function of OSS-SNR threshold for all frequencies are shown in Figure 4A. The shaded grey region depicts the separation point between the “motion” and “no motion data-sets”. The dashed cross-hair indicates the OSS-SNR threshold of 1.6 where 95% of all “no motion” voxels are eliminated. For this same subject the difference between |G*| of “motion” and “no motion” and the ratio of |G*|“motion” over |G*|“no-motion” have been plotted as a function of frequency in Figure 4B. In Figure 4 the boxes correspond to the 1st and 3rd quartiles, the horizontal line in each box is the median value, the ‘X’ corresponds to the maximum and minimum values, the small square in each box is the mean value, and the error bars (whiskers) represent a single standard deviation from the mean across all subjects. These plots show that at all frequencies except for 220 Hz it was feasible for at least one volunteer to have a mean OSS-SNR above 1.6. However, only the 140Hz frequency had a median OSS-SNR over all subjects just over 1.6, and a mean OSS-SNR just below the 1.6 threshold, (square in box plot). The 140 Hz vibration frequency also corresponded to having the highest percentage of voxels with OSS-SNR > 1.6.Cardiac MRE displacement fields can be imaged with mean OSS-SNR > 1.6 at frequencies as high as 180Hz, allowing for stiffness maps to be generated with direct inversion algorithms. However, octahedral shear strain signal to noise ratios and myocardial coverage was shown to be highest at a frequency of 140Hz across all subjects. This study motivates future evaluation of high-frequency 3D MRE in patient populations.