P. J. McCracken, A. Manduca, J. P. Felmlee, R. L. Ehman Radiology, Mayo Clinic and Foundation, Rochester, MN, United States, Physiology and Biophysics, Mayo Clinic and Foundation, Rochester, MN, United States Introduction Magnetic Resonance Elastography (MRE) is a recently described technique that quantifies material properties by measuring cyclic displacements of propagating shear waves. To date, most work in dynamic MRE has focused on the use of continuous harmonic mechanical excitation. However, mechanical transients may offer certain advantages in dynamic MRE, such as potentially simplifying the inversion process. Mechanical transients have been used to model traumatic brain injury, but there is still debate about the underlying material properties of the in-vivo human brain, which are often used in mathematical simulations of traumatic brain injury. We introduce the idea of using a transient impulse for mechanical excitation to interrogate stiffness in the brain. Methods We used transient mechanical shear waves of various periods to examine the brains of healthy volunteers (Figure 1a). We performed standard gradient echo imaging on a 1.5T GE Signa whole-body imager with additional motion encoding gradients used to detect and measure the shear wave propagation. Sixteen images of the shear wave were taken as it propagated through the head, using multiple gradients to effectively double the coverage of the mechanical impulse. The oscillating gradient pairs were synchronized to and encoded the wave motion. Several transient wave images have been displayed in Figure 1 for time intervals of 5 msec.