Coaxial excitation longitudinal shear wave measurement for quantitative elasticity assessment using phase-resolved optical coherence elastography
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Abstract:
Optical coherence elastography (OCE) is an emerging imaging modality for the assessment of mechanical properties in soft tissues. Transverse shear wave measurements using OCE can quantify the elastic moduli perpendicular to the force direction, however, missing the elastic information along the force direction. In this study, we developed coaxial excitation longitudinal shear wave measurements for quantification of elastic moduli along the force direction using M-scans. Incorporating Rayleigh wave measurements using non-coaxial lateral scans into longitudinal shear wave measurements, directionally dependent elastic properties can be quantified along the force direction and perpendicular to the force direction. Therefore, the reported system has the capability to image elasticity of anisotropic biological tissues.Keywords:
Elasticity
Shear waves
Acoustic Radiation Force
Coaxial
Elastography or elasticity imaging can be defined as the science and methodology of estimating the mechanical properties of a medium (including soft tissue). Elastography methods generally use an external source of force to produce a static or dynamic stress distribution on the probed medium. The applied stress causes a displacement distribution within the medium, which can be measured or imaged by ultrasound, magnetic resonance, or optical methods. In this paper, the relation of elastography to tissue pathology will be described and an overview of a number of recent patents will be provided. The most representative patents on both static and dynamic elastography methods will be presented, and emphasis will be given on the dynamic-based methods and devices that rely on the acoustic radiation force of ultrasound. A short reference will be also provided to patents on magnetic resonance elastography. Keywords: Acoustic radiation force, elasticity imaging, dynamic elastography, magnetic resonance elastography, shear waves, static elastography, viscoelastic media
Magnetic Resonance Elastography
Acoustic Radiation Force
Elasticity
Ultrasound Elastography
Shear waves
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Acoustic Radiation Force
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Purpose: The early recognition of changes in the pancreatic parenchyma plays an important role in the diagnosis of pancreatic disorders. The newly developed ultrasound technique of shearwave elastography or Acoustic Radiation Force Impulse Virtual Touch Tissue Quantification (ARFI-VTTQ) visualizes and quantifies tissue elasticity and superimposes findings on conventional B-scan images. Objective of the present study was to establish normal values for the ARFI-VTTQ method in healthy subjects.
Acoustic Radiation Force
Parenchyma
Echogenicity
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Ultrasound-based elastography including strain elastography, acoustic radiation force impulse (ARFI) imaging, point shear wave elastography and supersonic shear imaging (SSI) have been used to differentiate breast tumors among other clinical applications. The objective of this study is to extend a previously published virtual simulation platform built for ultrasound quasi-static breast elastography toward acoustic radiation force-based breast elastography. Consequently, the extended virtual breast elastography simulation platform can be used to validate image pixels with known underlying soft tissue properties (i.e. 'ground truth') in complex, heterogeneous media, enhancing confidence in elastographic image interpretations. The proposed virtual breast elastography system inherited four key components from the previously published virtual simulation platform: an ultrasound simulator (Field II), a mesh generator (Tetgen), a finite element solver (FEBio) and a visualization and data processing package (VTK). Using a simple message passing mechanism, functionalities have now been extended to acoustic radiation force-based elastography simulations. Examples involving three different numerical breast models with increasing complexity-one uniform model, one simple inclusion model and one virtual complex breast model derived from magnetic resonance imaging data, were used to demonstrate capabilities of this extended virtual platform. Overall, simulation results were compared with the published results. In the uniform model, the estimated shear wave speed (SWS) values were within 4% compared to the predetermined SWS values. In the simple inclusion and the complex breast models, SWS values of all hard inclusions in soft backgrounds were slightly underestimated, similar to what has been reported. The elastic contrast values and visual observation show that ARFI images have higher spatial resolution, while SSI images can provide higher inclusion-to-background contrast. In summary, our initial results were consistent with our expectations and what have been reported in the literature. The proposed (open-source) simulation platform can serve as a single gateway to perform many elastographic simulations in a transparent manner, thereby promoting collaborative developments.
Acoustic Radiation Force
Breast imaging
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Acoustic Radiation Force
Transient elastography
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Acoustic Radiation Force
Ultrasound Elastography
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This chapter reviews the current research and applications for acoustic radiation force (ARF)-based methods, namely ARF impulse (ARFI) imaging and shear wave elasticity imaging (SWEI) methods, in the diagnosis and treatment of cardiac diseases. ARFI imaging is an ultrasound-based elastography method that provides information about the local mechanical properties of tissue. SWEI imaging is another ARF-based elastography technique that uses acoustic impulses to displace tissue. SWEI and ARFI imaging are currently implemented on software-modified diagnostic ultrasound scanners and use conventional and prototype ultrasound transducers for the generation of radiation force and the tracking of the tissue response. Ultrasound elastography can provide direct tissue stiffness measurements throughout the cardiac cycle, and cardiac functional indices can be extracted from these mechanical measurements. Noninvasive measurement of cardiac stiffness through transthoracic imaging has great prognostic potential to diagnose a myriad of cardiomyopathies.
Acoustic Radiation Force
Ultrasound Elastography
Cardiac Imaging
Cardiac cycle
Ultrasonic imaging
Ultrasound imaging
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We aimed to evaluate the effectiveness of acoustic radiation force impulse (ARFI) elastography in differentiating between hepatic lesions. The prospective study included 117 patients with liver masses. Shear wave velocity (SWV) values for lesions were determined by ARFI imaging and compared statistically. The difference between SWV values for benign and malignant hepatic masses was significant ( p < 0.01). The threshold SWV value for malignant hepatic lesions was established at 2.52 m/s, and the sensitivity and specificity of this cut-off value were 97% and 66%, respectively. We concluded that ARFI elastography provides supplementary data that aid in the differential diagnosis of liver masses.
Acoustic Radiation Force
Wave velocity
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Acoustic Radiation Force
Transient elastography
Shear waves
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In present study, a high resolution acoustic radiation force elastography system based on a dual elements transducer was developed to distinguish the tissue elastic properties in micro-structures. The central frequency of the outer element of the transducer is 10 MHz, which was used to induce the localized displacement of tissue. The 50 MHz inner element was used to detect the localized displacement of tissue. In order to scan the tissue under different depths, the dual confocal ultrasound transducer was attached on a 3-axis motor system. After the ultrasonic backscattering signals from the tissue were recorded, the distributions of displacement under different locations and depths were calculated by cross-correlation algorithm. High resolution radiation force elastography was reconstructed by combining these distributions of displacements. System verifications were performed on tissue mimicking gelatin-based phantoms. The results demonstrated that the elastic difference and boundary between two different stiffness of phantom can be recognized by the high resolution image. In the future works, this system will be applied to scan the cornea tissue. Furthermore, the 3-D radiation force image will be constructed as well.
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