Single tracking location acoustic radiation force impulse viscoelasticity estimation (STL-VE): A method for measuring tissue viscoelastic parameters

Abstract

Single Tracking Location (STL) Shear wave Elasticity Imaging (SWEI) is a method for detecting elastic differences between tissues. It has the advantage of intrinsic speckle bias suppression compared to Multiple Tracking Location (MTL) variants of SWEI. However, the assumption of a linear model leads to an overestimation of the shear modulus in viscoelastic media. A new reconstruction technique denoted Single Tracking Location Viscosity Estimation (STL-VE) is introduced to correct for this overestimation. This technique utilizes the same raw data generated in STL-SWEI imaging. Here, the STL-VE technique is developed by way of a Maximum Likelihood Estimation (MLE) for general viscoelastic materials. The method is then implemented for the particular case of the Kelvin-Voigt Model. Using simulation data, the STL-VE technique is demonstrated and the performance of the estimator is characterized. Finally, the STL-VE method is used to estimate the viscoelastic parameters of ex-vivo bovine liver. We find good agreement between the STL-VE results and the simulation parameters as well as between the liver shear wave data and the modeled data fit.

Plane-Wave Imaging Improves Single-Track Location Shear Wave Elasticity Imaging

“…It should be large enough to capture the entire shear waveform [39], but small enough to minimize shear wave attenuation. A fixed track line spacing (transducer pitch) was used in all work reported in this study; therefore, we expect performance will vary when SWEI is conducted with other parameters.…”

Measurement of Liver Stiffness Using Shear Wave Elastography in a Rat Model: Factors Impacting Stiffness Measurement with Multiple- and Single-Tracking-Location Techniques

“…We previously discussed in Langdon et al (2015) that errors in rheological model choice can appear as beam spacing dependence. In this study, since we used cross-correlation to determine the wave speed (and thus, stiffness), the rheological model is effectively linear elastic.…”

“…Therefore, the beam spacing dependence observed in Figure 6 is to be expected. Unfortunately, we cannot simply apply a viscoelastic model without first considering the wave propagation geometry since this also impacts the estimate (Langdon et al, 2015). In that work, we utilized a Kelvin-Voigt model of viscoelasticity.…”

“…All of the following imaging experiments were performed using a Siemens Antares ultrasound scanner and our in-house elasticity software (Langdon and McAleavey, 2015). A VF 10-5 linear array transducer operating at 5.7 MHz, focal depth of 2 cm, a PRF of 10.5 kHz, and an F/# of 3.5 was used throughout the study.…”

“…In this work, estimates of the liver stiffness are made comparing both STL and MTL measurement using a cross-correlation of the pairs of impulsive shear wave excitations as in McAleavey et al (2007) and utilizing the GPU-based implementation discussed in Langdon and McAleavey (2015). The resulting measurements are compared to the METAVIR fibrosis score for the livers as determined by analysis of the histology by a board certified pathologist.…”