Modeling Bessel Acoustic Radiation Force Impulse Imaging with the k-Wave MATLAB Toolbox

Abstract

Shear wave elasticity imaging (SWEI) is a non-invasive technique to assess mechanical properties of tissue, including elasticity and viscoelasticity by introducing acoustic energy by introduction of a radiation force. Traditional Acoustic Radiation Force Impulse (ARFI) are produced by focused and unfocused beams. Due to diminished acoustic intensity outside the focal zone, focused ARFI posseses limited depth-of-field, beyond which elasticity estimates are unreliable. Imaging quality in unfocused beams on the other hand are limited to the Fraunhofer zone due to near-field oscillations of the pressure profile. We report a SWEI approach with Bessel apodized ARFI that can reduce diffraction in the Fresnel zone and at the same time retain a large high intensity focal illumination. We evaluate elastogram image quality produced by Gaussian focused and Bessel apodized ARF with time domain simulations using k-wave which is an open-source acoustic wave field toolbox. Our results show image quality evaluated by CNRdB improves from 6.04 in focused ARF SWEI images to 16.06 in Bessel ARF SWEI.