Quantification of Noise in Shear Wave Elasticity Imaging Caused by Speckle

Abstract

In time-of-flight shear wave elasticity imaging (SWEI), shear wave arrival times at laterally offset tracking positions are used for the reconstruction of the shear wave speed (SWS). Typically, regression filters along the lateral direction are used to smooth the noisy differential arrival times or, if divided by the tracking distance, the noisy shear wave slowness estimates. A major source of error in SWEI is based on the underlying speckle pattern. Thereby, the tracking position can be biased towards constructive interference of randomly distributed scatterers. Since the speckle effect is closely related to the parameters of the ultrasound imaging system, the quality of the SWS images depends on these parameters. In this contribution, the relationship between the variance of the slowness estimates and parameters such as the lateral and axial dimensions of the imaging point spread function, the segment length of the displacement estimation scheme, the lateral tracking distance and the impact of the actual shear wave speed was quantified through numerical simulations. The results provide a basis for an improved understanding of how speckle corrupts the SWS estimation.