Real Time Quantitative Elastography Using Supersonic Shear Wave Imaging (original) (raw)
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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.
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.
From supersonic shear wave imaging to full-field optical coherence shear wave elastography
Journal of Biomedical Optics, 2013
Elasticity maps of tissue have proved to be particularly useful in providing complementary contrast to ultrasonic imaging, e.g., for cancer diagnosis at the millimeter scale. Optical coherence tomography (OCT) offers an endogenous contrast based on singly backscattered optical waves. Adding complementary contrast to OCT images by recording elasticity maps could also be valuable in improving OCT-based diagnosis at the microscopic scale. Static elastography has been successfully coupled with full-field OCT (FF-OCT) in order to realize both micrometer-scale sectioning and elasticity maps. Nevertheless, static elastography presents a number of drawbacks, mainly when stiffness quantification is required. Here, we describe the combination of two methods: transient elastography, based on speed measurements of shear waves induced by ultrasonic radiation forces, and FF-OCT, an en face OCT approach using an incoherent light source. The use of an ultrafast ultrasonic scanner and an ultrafast camera working at 10,000 to 30;000 images∕s made it possible to follow shear wave propagation with both modalities. As expected, FF-OCT is found to be much more sensitive than ultrafast ultrasound to tiny shear vibrations (a few nanometers and micrometers, respectively). Stiffness assessed in gel phantoms and an ex vivo rat brain by FF-OCT is found to be in good agreement with ultrasound shear wave elastography.
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.
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.
Physics in Medicine and Biology, 2017
Non-invasive, quantitative methods to assess the properties of biological tissues are needed for many therapeutic and tissue engineering applications. Magnetic resonance elastography (MRE) has historically relied on external vibration to generate periodic shear waves. In order to focally assess a biomaterial or to monitor the response to ablative therapy, the interrogation of a specific region of interest by a focused beam is desirable and transient MRE (t-MRE) techniques have previously been developed to accomplish this goal. Also, strategies employing a series of discrete ultrasound pulses directed to increasing depths along a single line-of-sight have been designed to generate a quasi-planar shear wave. Such 'supersonic' excitations have been applied for ultrasound elasticity measurements. The resulting shear wave is higher in amplitude than that generated from a single excitation and the properties of the media are simply visualized and quantified due to the quasiplanar wave geometry and the opportunity to generate the wave at the site of interest. Here for the first time, we extend the application of supersonic methods by developing a protocol for supersonic transient magnetic resonance elastography (sst-MRE) using an MR-guided focused ultrasound system capable of therapeutic ablation. We apply the new protocol to quantify tissue elasticity in vitro using biologically-relevant inclusions and tissue-mimicking phantoms, compare the results with elasticity maps acquired with ultrasound shear wave elasticity imaging (US-SWEI), and validate both methods with mechanical testing. We found that a modified time-offlight (TOF) method efficiently quantified shear modulus from sst-MRE data, and both the TOF and local inversion methods result in similar maps based on US-SWEI. With a three-pulse excitation, the proposed sst-MRE protocol was capable of visualizing quasi-planar shear waves propagating away from the excitation location and detecting differences in shear modulus of 1 kPa. The techniques demonstrated here have potential application in real-time in vivo lesion detection and monitoring, with particular significance for image-guided interventions.
2002 IEEE Ultrasonics Symposium, 2002. Proceedings., 2002
Several tissue characterization techniques based on acoustic radiation force have been proposed to remotely excite soft tissues with ultrasound. Recently, in transient elastography, an ultrafast echographic device was developed to follow the propagation inside soft tissues of very low frequency shear waves (~100 Hz). These waves were generated using a vibrating system located at the body surface. In this paper, it is proposed to couple transient elastography and remote excitation techniques by replacing the usual external vibrating system by the use of the ultrasonic radiation force. In our experiments, the same probe allows both to generate and detect shear waves propagation by using an unusual emission-reception sequence. Our fully programmable electronics allow to induce and image, as desired, several shear sources at different times and locations in order to compute a real "shear wave beamforming" and optimize the shear source shape to the studied medium. An elasticity image of the whole medium can be recovered using only a few pushing beams (1 to 5). Measurements have been performed in several soft tissue mimicking phantom. Green's function based simulations have been used to support our experimental results.
Optics Letters, 2014
We report on the use of phase-sensitive optical coherence tomography (PhS-OCT) to detect and track temporal and spatial shear wave propagation within tissue, induced by ultrasound radiation force. Kilohertz-range shear waves are remotely generated in samples using focused ultrasound emission and their propagation is tracked using PhS-OCT. Cross-sectional maps of the local shear modulus are reconstructed from local estimates of shear wave speed in tissue-mimicking phantoms. We demonstrate the feasibility of combining ultrasound radiation force and PhS-OCT to perform high-resolution mapping of the shear modulus.