Ultrafast imaging of beamformed shear waves induced by the acoustic radiation force. Application to transient elastography (original) (raw)
Related papers
2015
Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) push beam to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity, by generating shear waves using a continuous mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a compression strain artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed (SWS) images were obtained by applying a local frequency estimation (LFE) method, capable of generating a 2D map from a single frame of shear wave motion, allowing for an imaging frame rate comparable to the vibration frequency. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥19 dB) between the target and background.
Shear wave elasticity imaging: a new ultrasonic technology of medical diagnostics
Ultrasound in Medicine & Biology, 1998
Shear wave elasticity imaging (SWEI) is a new approach to imaging and characterizing tissue structures based on the use of shear acoustic waves remotely induced by the radiation force of a focused ultrasonic beam. SWEI provides the physician with a virtual "finger" to probe the elasticity of the internal regions of the body. In SWEI, compared to other approaches in elasticity imaging, the induced strain in the tissue can be highly localized, because the remotely induced shear waves are attenuated fully within a very limited area of tissue in the vicinity of the focal point of a focused ultrasound beam. SWEI may add a new quality to conventional ultrasonic imaging or magnetic resonance imaging. Adding shear elasticity data ("palpation information") by superimposing color-coded elasticity data over ultrasonic or magnetic resonance images may enable better differentiation of tissues and further enhance diagnosis. This article presents a physical and mathematical basis of SWEI with some experimental results of pilot studies proving feasibility of this new ultrasonic technology. A theoretical model of shear oscillations in soft biological tissue remotely induced by the radiation force of focused ultrasound is described. Experimental studies based on optical and magnetic resonance imaging detection of these shear waves are presented. Recorded spatial and temporal profiles of propagating shear waves fully confirm the results of mathematical modeling. Finally, the safety of the SWEI method is discussed, and it is shown that typical ultrasonic exposure of SWEI is significantly below the threshold of damaging effects of focused ultrasound. © 1998 World Federation for Ultrasound in Medicine & Biology.
Shear elasticity probe for soft tissues with 1-D transient elastography
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
Important tissue parameters such as elasticity can be deduced from the study of the propagation of low frequency shear waves. A new method for measuring the shear velocity in soft tissues is presented in this paper. Unlike conventional transient elastography, in which the ultrasonic transducer and the low frequency vibrator are two separated parts, the new method relies on a probe that associates the vibrator and the transducer, which is built on the axis of the vibrator. This setup is easy to use. The low frequency shear wave is driven by the transducer itself that acts as a piston while it is used in pulse echo mode to acquire ultrasonic lines. The results obtained with the new method are in good agreement with those obtained with the conventional one.
Study of viscous and elastic properties of soft tissues using supersonic shear imaging
IEEE Symposium on Ultrasonics, 2003, 2003
Supersonic Shear imaging (SSI) is a new ultrasound based technique for real time visualization of soft tissue viscoelastic properties. Using ultrasound focused beams, it is possible to remotely generate inside the body mechanical sources radiating low frequency shear waves [1][2][3]. SSI is based on the ultrasonic generation of a shear source moving at a supersonic speed inside the body. In a complete analogy with the "sonic boom" created by a supersonic aircraft, the resulting shear waves will constructively interfere along a Mach cone, creating two intense plane waves. These plane shear waves propagate through the medium and are progressively distorted by tissue mechanical inhomogeneities. The ultrafast scanner developed in our laboratory (5000 images/s) is able to generate this supersonic source and image, in real time, the propagation of the resulting shear waves. Using inversion algorithms, viscosity and elasticity maps of the medium can be deduced from this shear wave propagation movie. Creating such a supersonic regime enables quantitative tissue elasticity mapping in less than 20 ms, even in strongly viscous medium like breast or liver. Results validating SSI for quantitative shear elasticity mapping in heterogeneous tissue mimicking phantoms are presented. Detection of in vitro thermally-induced lesions on fresh tissue samples is shown. In vivo tests made on healthy volunteers show the potential clinical applicability of SSI for breast cancer detection. Finally, viscosity mapping using SSI has been studied theoretically and experimentally. Based on a Voigt model, simulations in different viscous and elastic media were compared and fitted to in vitro experiments. Using this theoretical background, viscosity maps using SSI were for the first time derived in viscoelastic phantoms.
On the effects of reflected waves in transient shear wave elastography
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
In recent years, novel quantitative techniques have been developed to provide noninvasive and quantitative stiffness images based on shear wave propagation. Using radiation force and ultrafast ultrasound imaging, the supersonic shear imaging technique allows one to remotely generate and follow a transient plane shear wave propagating in vivo in real time. The tissue shear modulus, i.e., its stiffness, can then be estimated from the shear wave local velocity. However, because the local shear wave velocity is estimated using a timeof-flight approach, reflected shear waves can cause artifacts in the estimated shear velocity because the incident and reflected waves propagate in opposite directions. Such effects have been reported in the literature as a potential drawback of elastography techniques based on shear wave speed, particularly in the case of high stiffness contrasts, such as in atherosclerotic plaque or stiff lesions. In this letter, we present our implementation of a simple directional filter, previously used for magnetic resonance elastography, which separates the forward-and backward-propagating waves to solve this problem. Such a directional filter could be applied to many elastography techniques based on the local estimation of shear wave speed propagation, such as acoustic radiation force imaging (ARFI), shearwave dispersion ultrasound vibrometry (SDUV), needle-based elastography, harmonic motion imaging, or crawling waves when the local propagation direction is known and high-resolution spatial and temporal data are acquired.
2008 IEEE Ultrasonics Symposium, 2008
ShearWave TM Elastography (SWE) is a new real time ultrasound imaging mode that quantitatively measures local tissue elasticity in kPa. Based on the Supersonic Shear Imaging concept (developped at the Laboratoire Ondes et Acoustique, Paris), this new concept may appear as a promising tool to improve breast lesion characterization. In vitro experimental measurements have been performed to quantify SWE mode performances in terms of resolution, penetration and the ability to measure quantitatively elasticity. Results show that the SWE mode exhibits a millimetric resolution and quantifies properly tissue elasticity on a wide range of elastic contrasts (from 7 to 110 kPa). The real time capabilities and the robustness of the mode have been tested in clinical conditions, on breast lesions. 150 patients have been scanned with SWE mode in three different sites. Results show that SWE performs well on breast pathologies and presents a very good inter-site reproducibility. Finally, the quantitative elasticity value was analyzed as a function of pathology using FNA or core biopsy as the reference diagnostic method.
2008
ShearWave TM Elastography (SWE) is a new real time ultrasound imaging mode that quantitatively measures local tissue elasticity in kPa. Based on the Supersonic Shear Imaging concept (developped at the Laboratoire Ondes et Acoustique, Paris), this new concept may appear as a promising tool to improve breast lesion characterization. In vitro experimental measurements have been performed to quantify SWE mode performances in terms of resolution, penetration and the ability to measure quantitatively elasticity. Results show that the SWE mode exhibits a millimetric resolution and quantifies properly tissue elasticity on a wide range of elastic contrasts (from 7 to 110 kPa). The real time capabilities and the robustness of the mode have been tested in clinical conditions, on breast lesions. 150 patients have been scanned with SWE mode in three different sites. Results show that SWE performs well on breast pathologies and presents a very good inter-site reproducibility. Finally, the quantitative elasticity value was analyzed as a function of pathology using FNA or core biopsy as the reference diagnostic method.
Real Time Quantitative Elastography Using Supersonic Shear Wave Imaging
2010 7th Ieee International Symposium on Biomedical Imaging: from Nano to Macro, 2010
Supersonic Shear Imaging (SSI) is a quantitative stiffness imaging technique based on the combination of a radiation force induced in tissue by an ultrasonic beam and ultrafast ultrasound imaging sequence (up to more than 10000 frames per second) catching in real time the propagation of the resulting shear waves. Local shear wave speed is estimated and enables the two dimensional mapping of shear elasticity. This imaging modality is implemented on conventional probes driven by dedicated ultrafast echographic devices and can be performed during a standard ultrasound exam. The clinical potential of SSI is today extensively investigated for many potential applications such as breast cancer diagnosis, liver fibrosis staging, cardiovascular applications, ophthalmology. This invited lecture presents a short overview of the current investigated applications of SSI.
Supersonic shear imaging: a new technique for soft tissue elasticity mapping
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
Supersonic shear imaging (SSI) is a new ultrasound-based technique for real-time visualization of soft tissue viscoelastic properties. Using ultrasonic focused beams, it is possible to remotely generate mechanical vibration sources radiating low-frequency, shear waves inside tissues. Relying on this concept, SSI proposes to create such a source and make it move at a supersonic speed. In analogy with the "sonic boom" created by a supersonic aircraft, the resulting shear waves will interfere constructively along a Mach cone, creating two intense plane shear waves. These waves propagate through the medium and are progressively distorted by tissue heterogeneities. An ultrafast scanner prototype is able to both generate this supersonic source and image (5000 frames/s) the propagation of the resulting shear waves. Using inversion algorithms, the shear elasticity of medium can be mapped quantitatively from this propagation movie. The SSI enables tissue elasticity mapping in less than 20 ms, even in strongly viscous medium like breast. Modalities such as shear compounding are implementable by tilting shear waves in different directions and improving the elasticity estimation. Results validating SSI in heterogeneous phantoms are presented. The first in vivo investigations made on healthy volunteers emphasize the potential clinical applicability of SSI for breast cancer detection.
2005
Acoustic Radiation Force Impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and ultrasonic correlation-based methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm 3 , pulse durations are less than 1 msec, and tissue displacements are typically several microns. Displacement is quantified using interpolation and cross correlation methods. Noise reduction is accomplished by adaptively filtering the temporal response, and median filters are applied to the resulting images. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g. fat) displacing farther than stiffer tissues (e.g. muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include: soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from ongoing studies are presented.