Intracardiac measurements of elasticity using Acoustic Radiation ForceImpulse (ARFI) methods: Temporal and spatial stability of shear wave velocimetry

Acoustic Radiation Force Impulse (ARFI) methods have been validated formeasuring tissue elastic properties, with shear wave velocimetry emerging as aquantitative way to measure stiffness. Using ultrasound to interrogate cardiacelasticity holds promise for diagnosis of cardiac dysfunction, but acquiringmeasurements has previously been an invasive procedure and not clinicallyviable. This work describes the feasibility of generating and tracking acousticradiation force generated shear waves in myocardium with an intracardiacechocardiography (ICE) transducer and discusses the spatial and temporalstability of these measurements. In vivo healthy canine data are presented,demonstrating the quantitative contrast of systolic and diastolic shearvelocities in the right ventricular free wall (RVFW) as measured by thistechnique. Although the generated shear wave amplitudes are low, ICE shear-wavevelocimetry is shown to provide a much less invasive way to quantify the heart'sstiffening and relaxation through systole and diastole than prior methods.