Comb-Push Ultrasound Shear Elastography (CUSE) With Various Ultrasound Push Beams

Abstract

Comb-push Ultrasound Shear Elastography (CUSE) has recently been shown to be a fast and accurate two-dimensional (2D) elasticity imaging technique that can provide a full field-of- view (FOV) shear wave speed map with only one rapid data acquisition. The initial version of CUSE was termed U-CUSE because unfocused ultrasound push beams were used. In this paper, we present two new versions of CUSE – Focused CUSE (F-CUSE) and Marching CUSE (M-CUSE), which use focused ultrasound push beams to improve acoustic radiation force penetration and produce stronger shear waves in deep tissues (e.g. kidney and liver). F-CUSE divides transducer elements into several subgroups which transmit multiple focused ultrasound beams simultaneously. M-CUSE uses more elements for each focused push beam and laterally marches the push beams. Both F-CUSE and M-CUSE can generate comb-shaped shear wave fields that have shear wave motion at each imaging pixel location so that a full FOV 2D shear wave speed map can be reconstructed with only one data acquisition. Homogeneous phantom experiments showed that U-CUSE, F-CUSE and M-CUSE can all produce smooth shear wave speed maps with accurate shear wave speed estimates. An inclusion phantom experiment showed that all CUSE methods could provide good contrast between the inclusion and background with sharp boundaries while F-CUSE and M-CUSE require shorter push durations to achieve shear wave speed maps with comparable SNR to U-CUSE. A more challenging inclusion phantom experiment with a very stiff and deep inclusion shows that better shear wave penetration could be gained by using F-CUSE and M-CUSE. Finally, a shallow inclusion experiment showed that good preservations of inclusion shapes could be achieved by both U-CUSE and F-CUSE in the near field. Safety measurements showed that all safety parameters are below FDA regulatory limits for all CUSE methods. These promising results suggest that, using various push beams, CUSE is capable of reconstructing a 2D full FOV shear elasticity map using only one push-detection data acquisition in a wide range of depths for soft tissue elasticity imaging.

Ultrasound Elastography: The New Frontier in Direct Measurement of Muscle Stiffness

“…SSI produces 2D quantitative images of the Young modulus superimposed on B-mode images (Figure 4). Although the region of interest, or measurement area, in SWE is small, newer techniques are being developed that permit dynamic measurements and increase the region of interest (30,43). Since tissue deformation in SSI relies on highly controlled ultrasound push beams rather than on tissue compression by the sonographer, SSI is considerably less operator dependent than SE.…”

Fast Shear Compounding Using Robust 2-D Shear Wave Speed Calculation and Multi-directional Filtering

“…In this study a curved linear array transducer C5-2v (Verasonics Inc., Redmond, WA, center frequency = 3 MHz) was used to produce differently angled shear waves by using different parts of the curvature of the probe. A comb-push technique as introduced in (Song et al 2012; Song et al 2013) was used to transmit multiple push beams simultaneously at different parts of the curvature of the probe so that multiple differently angled shear waves can be produced in the FOV at the same time. A Verasonics ultrasound system (Verasonics Inc., Redmond, WA) was used to produce the ultrasound push beam and track the resulting shear wave motion.…”

“…Therefore, conventional shear wave speed estimation methods that assume a lateral propagation direction produce biased estimates of shear wave speed (Palmeri et al 2008; Tanter et al 2008; Rouze et al 2010; Wang et al 2010). To address these challenges, this study proposes a fast shear compounding method that: 1. uses a comb-push (Song et al 2012; Song et al 2013) to produce multiple differently angled shear waves simultaneously to achieve shear compounding with only one push-detect data acquisition, so that shear wave imaging frame rate is preserved and motion artifacts are minimized; 2. uses a multi-directional filter to isolate shear waves with different propagation directions and a robust two-dimensional (2D) shear wave speed calculation method to accurately reconstruct 2D shear wave speed maps from each direction which are then compounded into a final map.…”

Fast shear compounding using directional filtering and two-dimensional shear wave speed calculation

“…A comb-push [7,8] was implemented on a curved array C4-2 (Philips Healthcare, Andover, MA) to transmit 5 unfocused push beams simultaneously, producing a total of 8 shear waves with 8 different propagation directions within the FOV, as shown in Fig. 4.…”