Figure 2.

Schematic diagram of the magnetic resonance elastography system. Conventional MR imaging gradients and RF pulses that encode spatial positions are shown at the bottom left. The electromechanical actuator (a) applies vertical displacement to the object to be imaged via a cradle or (b) horizontal displacement via a bite block (right). The cyclic motion-sensitizing gradients and the actuator are synchronized using trigger pulses provided by the imager. The phase offset (θ) between the two can be varied to image the waves at various stages of propagation. As shown by the shaded regions, the motion-sensitizing gradients can be superimposed along any desired axis to detect that component of the cyclic motion vector. All data was collected and analyzed using 100 Hz motion.