Sources of Variability in Shear Wave Speed and Dispersion Quantification with Ultrasound Elastography: A Phantom Study

Abstract

There is a growing interest in quantifying shear-wave dispersion (SWD) with ultrasound shear-wave elastography (SWE). Recent studies suggest that SWD complements shear-wave speed (SWS) in diffuse liver disease diagnosis. To accurately interpret these metrics in clinical practice, we analyzed the impact of operatordependent acquisition parameters on SWD and SWS measurements. Considered parameters were the acquisition depth, lateral position and size of the region of interest (ROI), as well as the size of the SWE acquisition box. Measurements were performed using the Canon Aplio i800 system (Canon Medical Systems, Otawara, Tochigi, Japan) and four homogeneous elasticity phantoms with certified stiffness values ranging from 3.7 to 44 kPa. In general, SWD exhibited two to three times greater variability than SWS. The acquisition depth was the main variance-contributing factor for both SWS and SWD, which decayed significantly with depth. The lateral ROI position contributed as much as the acquisition depth to the total variance in SWD. Locations close to the initial shear-wave excitation pulse were more robust to biases because of inaccurate probeÀphantom coupling. The size of the ROI and acquisition box did not introduce significant variations. These results suggest that future guidelines on multiparametric elastography should account for the depth-and lateral-dependent variability of measurements.

Shear wave velocity values measured by 2D‐shear wave elastography are not different between awake and anesthetized cats without clinically significant hepatic fibrosis

“…Shear wave dispersion is the frequency dependence of shear waves in viscous media and dispersion values have been found to decrease with acquisition depth along with shear wave speeds. 20 It is possible that the shallow depth of the ROI's due to small liver size in this study contributed to the variation of values; however, the evaluation of the effects of depth and viscoelasticity was beyond the scope of this study. Second, shear wave elastography and liver biopsy were performed on a small number of cats.…”

Shear wave elastography and shear wave dispersion correlated to biopsy at the scheduled follow‐up of pediatric liver grafts

“…SWD reflects tissue characteristics other than fibrosis, and multiple factors can alter tissue viscosity 29,30 . It is important to elucidate what conditions affect liver viscosity in terms of increased SWD values.…”

“…SWD reflects tissue characteristics other than fibrosis, and multiple factors can alter tissue viscosity. 29,30 It is important to elucidate what conditions affect liver viscosity in terms of increased SWD values. Other than inflammation, cholestasis, ischemia, ascites, congestion and vasculopathies have been reported to modify tissue viscosity.…”

Review of imaging test phantoms

“…Similarly, the acoustic characteristics of the phantom, including speed of sound, impedance, and attenuation, need to be carefully tuned. This enables the phantom to provide an accurate response to the acoustic receiver, replicating the acoustic behavior observed in human tissues 9 , 10 . The mechanical properties of the material, including stiffness, modulus, and density, play a crucial role in ensuring that the phantom exhibits the desired tactile feel, particularly in the experiments requiring physical interaction.…”

“…The mechanical properties of the material, including stiffness, modulus, and density, play a crucial role in ensuring that the phantom exhibits the desired tactile feel, particularly in the experiments requiring physical interaction. For instance, in the case of pulsing arterial phantoms, the material’s behavior under pressurized conditions is of particular importance 10 . The shape of the phantom is another critical parameter that significantly impacts its behavior.…”