Phase Aberration and Attenuation Effects on Acoustic Radiation Force-Based Shear Wave Generation

Abstract

Tissue elasticity is measured by shear wave elasticity imaging methods using acoustic radiation force to create the shear waves. Phase aberration and tissue attenuation can hamper the generation of shear waves for in vivo applications. In this study effects of phase aberration and attenuation in ultrasound focusing for creating shear waves were explored. This includes the effects of phase shifts and amplitude attenuation on shear wave characteristics such as shear wave amplitude, shear wave speed, shear wave center frequency and bandwidth. Two samples of swine belly tissue were used to create phase aberration and attenuation experimentally. To explore the phase aberration and attenuation effects individually, tissue experiments were complemented with ultrasound beam simulations using FOCUS and shear wave simulations using Finite Element Model (FEM) analysis. The ultrasound frequency used to generate shear waves was varied from 3.0 to 4.5 MHz. Results The measured acoustic pressure and resulting shear wave amplitude decreased approximately 40% to 90% with the introduction of the tissue samples. Acoustic intensity and shear wave displacement were correlated for both tissue samples, the resulting Pearson’s correlation coefficients were 0.99 and 0.97. Analysis of shear wave generation with tissue samples (Phase Aberration and Attenuation case), measured phase screen (Only Phase Aberration case) and FOCUS/FEM model (Only Attenuation case) showed that tissue attenuation affected the shear wave generation more than tissue aberration. Decreasing the ultrasound frequency helped maintain a focused beam for creation of shear waves in the presence of both phase aberration and attenuation.

Attenuation measuring ultrasound shearwave elastography andin vivoapplication in post-transplant liver patients

“…The AMUSE method is also dependent on other general limitations of ultrasound-based shear wave elastography methods that rely on acoustic radiation force to generate the shear waves. The AMUSE method requires robust wave generation with the acoustic radiation force beam and motion detection methods to track waves that could be affected by phase aberration and attenuation (Amador et al , 2016; Carrascal et al , 2016). …”

Guidelines for Finite-Element Modeling of Acoustic Radiation Force-Induced Shear Wave Propagation in Tissue-Mimicking Media

“…This has been employed in the results shown in this article. This symmetry may be disrupted if phase aberration due to inhomogeneity in compressional wave speed is considered [59]. The compressional sound speed inhomogeneities produced by subcutaneous fat and muscle layers, which could induce changes in ultrasound propagation time-of-flight and cause errors in beam focusing, would not uniformly distributed, so a full 3D model would be necessary to account for these inhomogeneities.…”

“…The compressional sound speed inhomogeneities produced by subcutaneous fat and muscle layers, which could induce changes in ultrasound propagation time-of-flight and cause errors in beam focusing, would not uniformly distributed, so a full 3D model would be necessary to account for these inhomogeneities. One assumption that could be made is that a phase screen, an adjustment of electronic focusing delays, could be applied across the elevation direction of the transducer [59]. …”

Production of acoustic radiation force using ultrasound: methods and applications

“…However, different tissues have different longitudinal velocities that will cause imperfect focusing. This is particularly exaggerated when large subcutaneous fat layers are encountered both due to increased ultrasound attenuation and lower longitudinal velocity (~1450 m/s) [165]. As a result, these tissue inhomogeneities in longitudinal velocity cause phase alterations between different ultrasound waves, or phase aberration.…”