Comparison of Motion Encoding Waveforms for Magnetic Resonance Elastography at 3T.

Magnetic resonance (MR) elastography has the ability to combine the inherent soft-tissue contrast of traditional MR imaging with quantitative maps of tissue stiffness. Mechanical properties of tissues can vary greatly with disease and degeneration, and can illuminate structure-function understanding of tissues. Dynamic MR elastography is a phase contrast-based method for imaging the transmission of strain waves in an object. The present study evaluates the theoretical and empirical results of using trapezoidal and sinusoidal motion encoding gradients (MEGs) for the purposes of elastography at 3T. The study evaluated the phase-to-noise ratio for the methods, and found excellent agreement between the theoretical predictions and experimental results. The sinusoidal MEGs were predicted to have a relative PNR decrease of 21.5%, which compares very well with the experimental PNR decrease of 19.1% (95% CI = 17.1% to 21.0%). These results show the trapezoidal MEGs provide more sensitivity to strain wave transmission for the purposes of MR elastography.