Single Breath Hold Transient MR-Elastography of the Heart - Imaging Pulsed Shear Wave Propagation induced by Aortic Valve Closure -
Robert B, Gennisson J, Tanter M, Fink M, Sinkus R
Laboratoire Ondes et Acoustique
Pulsed transient shear waves, generated by aortic valve closure, are visualized in the septum by a motion-sensitized balanced FFE sequence. Motion-sensitization is achieved by adding a sinusoidal gradient coding waves at 300Hz. Acquisition is performed in a single breath hold using a retrospectively gated ECG-triggered sequence, which is phase-locked to mechanical vibrations at 300Hz. 20 heart phases are acquired. Phase-profiles through the septum reveal the presence of shear waves present shortly after aortic valve closure. Identical experiments without a motion-sensitized gradient yield phase-profiles identical during the entire cardiac cycle. Obtained values for shear wave speed agree with findings from ultrasound.