Research Overview

Acoustic radiation force (ARF) is a phenomenon associated with the propagation of acoustic waves in attenuating media. Attenuation includes both scattering and absorption of the acoustic wave. Attenuation is a frequency dependent phenomenon, and in soft tissues it is dominated by absorption. With increasing acoustic frequencies, the tissue does not respond fast enough to the transitions between positive and negative pressures, thus its motion becomes out of phase with the acoustic wave, and energy is deposited into the tissue. This energy results in both a net force in the direction of wave propagation, and tissue heating. The force causes a displacement of the tissue, and the time scale of this response is much slower than that of the acoustic propagation.

Shear Wave Elasticity Imaging (SWEI) is the tracking and characterization of outwardly propagating shear waves generated by the delivery of an impulsive excitation: we use an ARF impulse. These shear waves vary in speed, spatial and temporal frequency content, and amplitude depending on the ARF impulse configuration and material properties of the tissue. Understanding the behavior of shear waves in tissue can provide key information as to its mechanical properties.

Our laboratory is currently developing novel methods for utilizing ARF techniques and ARF-based SWEI to characterize the mechanical properties of soft tissues for clinically-relevant applications, such as tumor-detection, progression of neurodegenerative pathologies, liver fibrosis, and nerve stiffening.