A harmonic tracking method for Acoustic Radiation Force Impulse (ARFI) imaging

Ultrasound-based elasticity imaging methods, such as Acoustic Radiation Force Impulse (ARFI) imaging, rely upon the accurate estimation of displacements to characterize the mechanical response of soft tissues. Sources of clutter, such as off-axis scattering and reverberation, can corrupt displacement estimates and result in noisy images. In this work, we investigated the use of filter-based and pulse inversion harmonic tracking methods to monitor the displacements induced by an ARFI excitation. A fully sampled method was developed that improves the temporal sampling frequency associated with the pulse inversion technique. Implemented on a conventional scanner, the harmonic tracking methods are compared with conventional ARFI imaging techniques that use the fundamental component of the received beam in phantoms and in vivo. In phantoms, where the generated harmonics are minimal, the harmonic and fundamental methods provided similar results. Decreased jitter and improved feature detection in ARFI images were obtained with harmonic tracking methods in vivo.