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

Acoustic Radiation Force Impulse (ARFI) methods have been validated for measuring tissue elastic properties, with shear wave velocimetry emerging as a quantitative way to measure stiffness. Using ultrasound to interrogate cardiac elasticity holds promise for diagnosis of cardiac dysfunction, but acquiring measurements has previously been an invasive procedure and not clinically viable. This work describes the feasibility of generating and tracking acoustic radiation force generated shear waves in myocardium with an intracardiac echocardiography (ICE) transducer and discusses the spatial and temporal stability of these measurements. In vivo healthy canine data are presented, demonstrating the quantitative contrast of systolic and diastolic shear velocities in the right ventricular free wall (RVFW) as measured by this technique. Although the generated shear wave amplitudes are low, ICE shear-wave velocimetry is shown to provide a much less invasive way to quantify the heart's stiffening and relaxation through systole and diastole than prior methods.