Shear Modulus Imaging with Spatially-Modulated Ultrasound Radiation Force

Abstract

The application of Spatially Modulated Ultrasound Radiation Force (SMURF) to shear modulus imaging is demonstrated in tissue mimicking phantoms and porcine liver. Scanning and data acquisition was performed with a Siemens Antares ultrasound scanner and VF7-3 linear array operating at 4.21 MHz. Modulus estimates in uniform phantoms of Zerdine™ with shear moduli of 5.1 and 12.4 kPa exhibited standard deviations within 6% of the mean value. Zerdine spheres 1 cm in diameter (nominally 2.7, 4.7, and 15 kPa) in a 8 kPa (nominal) background are clearly resolved. Cross sectional images of a soft conical inclusion in a gelatin-based phantom indicate a spatial resolution of approximately 2.5 mm. Images of the shear modulus of an ex-vivo sample of porcine liver tissue show an average value of 3kPa. A stiff lesion induced with 0.5 mL of 10% glutaraldehyde is clearly visible as a region of shear modulus in excess of 10 kPa. A modulus gradient associated with the diffusion of the glutaraldehyde is visible. Two pulse sequences were examined, differing only in the timing of the beams used to generate the shear waves. Details of the beam sequences and subsequent signal processing are presented.

Single- and Multiple-Track-Location Shear Wave and Acoustic Radiation Force Impulse Imaging: Matched Comparison of Contrast, Contrast-to-Noise Ratio and Resolution

“…(Sarvazyan et al, 1998), and first demonstrated in vivo by our group (Nightingale et al, 2003), quantifies tissue stiffness by exciting the tissue with an ARFI push beam and monitoring the associated shear wave propagation through the region of interest. Time-of-flight (TOF) based reconstruction algorithms are then used to estimate the shear wave speed (SWS) (Palmeri et al, 2008; Wang et al, 2010; Rouze et al, 2010; Muller et al, 2009; Tanter et al, 2008; McAleavey et al, 2009; McLaughlin and Renzi, 2006; Chen et al, 2004), which in linear elastic materials is proportional to the square root of the shear modulus G divided by the density ρ: $$\mathrm{normalS}\mathrm{normalW}\mathrm{normalS}=\sqrt{\frac{G}{\rho }}$$ SWS typically has units of m/s, G has units of kPa, and ρ has units of kg/m 3 and is generally assumed to be close to that of water (1000 kg/m 3 ) in tissue.…”

“…al. (McAleavey et al, 2009). Mathematically, it can be considered as finding the partial derivative of the arrival times T with respect to x p instead of x t : $$\mathrm{normalS}\mathrm{normalW}{\mathrm{S}}_{\mathrm{normalS}\mathrm{normalT}\mathrm{normalL}}false(z,x_t,x_{p}false)=\text{sgn}false(x_p-x_{t}false){true(\frac{\partial Tfalse(z,x_t,x_{p}false)}{\partial x_p}true)}^{-1}$$ Rather than tracking the speed of a single propagating shear wave going through multiple tracking locations, this approach employs multiple, laterally-offset push beams and a single tracking location.…”

A multiresolution approach to shear wave image reconstruction

“…Meanwhile, McAleavey et al . [20] used a spatially-modulated source function to estimate shear velocity from a single recording location, and extended the method to create images using a fixed spatial distance between the source functions and the receive location [21], [22], trading tracking waves from a single excitation at multiple track locations for tracking a single location, and using a synthetic shear wave generated from multiple offset excitations. Bercoff et al .…”

Non-invasive and Non-destructive Characterization of Tissue Engineered Constructs Using Ultrasound Imaging Technologies: A Review

“…69 Shear modulus can be estimated with improved accuracy by applying spatially modulated ultrasound radiation force. 46 …”