Physical Principles of Elastography: A Primer for Radiologists (original) (raw)
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Ultrasound elastography: principles and techniques
Diagnostic and interventional imaging, 2013
Ultrasonography has been widely used for diagnosis since it was first introduced in clinical practice in the 1970's. Since then, new ultrasound modalities have been developed, such as Doppler imaging, which provides new information for diagnosis. Elastography was developed in the 1990's to map tissue stiffness, and reproduces/replaces the palpation performed by clinicians. In this paper, we introduce the principles of elastography and give a technical summary for the main elastography techniques: from quasi-static methods that require a static compression of the tissue to dynamic methods that uses the propagation of mechanical waves in the body. Several dynamic methods are discussed: vibro-acoustography, Acoustic Radiation Force Impulsion (ARFI), transient elastography, shear wave imaging, etc. This paper aims to help the reader at understanding the differences between the different methods of this promising imaging modality that may become a significant tool in medical imag...
Ultrasound elastography applications
Community Based Medical Journal, 2013
Ultrasound elastography (EUS) is a method to assess the mechanical properties of tissue, by applying stress and detecting tissue displacement using ultrasound. There are several EUS techniques used in clinical practice; strain (compression) EUS is the most common technique that allows real-time visualisation of the elastographic map on the screen. There is increasing evidence that EUS can be used to measure the mechanical properties of musculoskeletal tissue in clinical practice, with the future potential for early diagnosis to both guide and monitor therapy. This review describes the various EUS techniques available for clinical use, presents the published evidence on musculoskeletal applications of EUS and discusses the technical issues, limitations and future perspectives of this method in the assessment of the musculoskeletal system. Ultrasound elastography (EUS) is a recently developed ultrasound-based method, which allows the qualitative visual or quantitative measurements of the mechanical properties of tissue 1 . The technique was first introduced in vitro in the early 1990s, and subsequently evolved into a real-time tool for in vivo imaging of the distribution of tissue strain and elastic modulus 2. EUS provides information on tissue stiffness, which complements and is independent from the acoustic impedance and vascular flow information provided by Bmode and Doppler imaging, thus opening a new dimension in diagnostic imaging 3 . EUS is based upon the general principle that stress applied to tissue causes changes within it, which depend on the elastic properties of tissue 3 . Over the years of research on elasticity, there have been several approaches of EUS, resulting in different methods, depending on the way of tissue stress application and the used method to detect and construct an image of tissue displacement 3 . Strain (compression) EUS is the commonest technique that allows real-time visualisation of the image on the screen, and it has been successfully employed to detect and characterise lesions in a variety of tissues and organs 5 . Disease in the musculoskeletal system results in alterations to its biomechanical properties. Although EUS techniques have been extensively employed for in vitro research of muscle and tendon biomechanics since the early 1990s 6 , the recent introduction of EUS into commercially available ultrasound systems has driven research activity towards potential clinical applications of this novel method in the musculoskeletal system 7 . This review aims to describe the various EUS techniques available for clinical use, present the available published evidence on musculoskeletal applications of EUS, and finally discuss the limitations and future perspectives of this technique for assessing the musculoskeletal system.
Shear-Wave Elastography: Basic Physics and Musculoskeletal Applications
RadioGraphics
In the past 2 decades, sonoelastography has been progressively used as a tool to help evaluate soft-tissue elasticity and add to information obtained with conventional gray-scale and Doppler ultrasonographic techniques. Recently introduced on clinical scanners, shearwave elastography (SWE) is considered to be more objective, quantitative, and reproducible than compression sonoelastography with increasing applications to the musculoskeletal system. SWE uses an acoustic radiation force pulse sequence to generate shear waves, which propagate perpendicular to the ultrasound beam, causing transient displacements. The distribution of shear-wave velocities at each pixel is directly related to the shear modulus, an absolute measure of the tissue's elastic properties. Shear-wave images are automatically coregistered with standard B-mode images to provide quantitative color elastograms with anatomic specificity. Shear waves propagate faster through stiffer contracted tissue, as well as along the long axis of tendon and muscle. SWE has a promising role in determining the severity of disease and treatment followup of various musculoskeletal tissues including tendons, muscles, nerves, and ligaments. This article describes the basic ultrasound physics of SWE and its applications in the evaluation of various traumatic and pathologic conditions of the musculoskeletal system. ©
Principles of ultrasound elastography
Abdominal radiology (New York), 2018
Tissue stiffness has long been known to be a biomarker of tissue pathology. Ultrasound elastography measures tissue mechanical properties by monitoring the response of tissue to acoustic energy. Different elastographic techniques have been applied to many different tissues and diseases. Depending on the pathology, patient-based factors, and ultrasound operator-based factors, these techniques vary in accuracy and reliability. In this review, we discuss the physical principles of ultrasound elastography, discuss differences between different ultrasound elastographic techniques, and review the advantages and disadvantages of these techniques in clinical practice.
Real-time quasi-static ultrasound elastography
Interface Focus, 2011
Ultrasound elastography is a technique used for clinical imaging of tissue stiffness with a conventional ultrasound machine. It was first proposed two decades ago, but active research continues in this area to the present day. Numerous clinical applications have been investigated, mostly related to cancer imaging, and though these have yet to prove conclusive, the technique has seen increasing commercial and clinical interest. This paper presents a review of the most widely adopted, non-quantitative, techniques focusing on technical innovations rather than clinical applications. The review is not intended to be exhaustive, concentrating instead on placing the various techniques in context according to the authors' perspective of the field.
IFMBE Proceedings, 2015
Shear wave elastography (SWE) is an imaging technique using ultrafast ultrasound (20k fps) to measure tissue elasticity. This study aimed to verify the accuracy of SWE measurement compared to the gold standard and investigate the effects of size, depth, stiffness and overlapping of lesions on SWE measurements. A tissue-mimicking phantom with acoustic and shear elasticity properties similar to human breast was developed. The masses' elasticity was measured using a commercial SWE scanner and an electromechanical microtester (gold standard). Statistically significant difference (p<0.05) was found between the elasticity values measured using SWE and the gold standard, whereby the SWE overestimated the elasticity by a mean of 22.79±15.00 kPa. This overestimation might be due to the artefacts caused by wave interferences between the elasticity boundaries. Size and depth of lesions did not affect SWE measurement, however the depth of shear wave detection was limited to 8 cm from the surface.
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 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.