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Single Track Location Shear Wave Elasticity Imaging (STL-SWEI) creates high resolution shear wave speed maps by comparing the tissue motion at each tracking location between spatially-offset radiation force excitations. While STL-SWEI circumvents the resolution-limiting effects of speckle noise, it requires a series of excitation-tracking ensembles to build up a lateral field of view, increasing the...
Shear wave elastography is useful for quantitatively evaluating tissue elasticity by measuring the speed of a shear wave induced within the body by acoustic radiation force. We proposed a pushing-and-tracking sequence, coded push-pulse excitation to increase the signal-to-noise ratio (SNR) of the observed shear wave propagation without increasing measurement time and push-pulse amplitude1). In this...
Recently we demonstrated non-contact excitation of broadband mechanical waves in soft media for transient elastography. Using US from an air-coupled transducer focused on an air/medium interface, this method (called “acoustic micro-tapping”, or AμT) provides sufficient radiation force to launch a transient displacement. Combined with ultrafast phase sensitive OCT, AμT-OCT can track propagating mechanical...
Point shear wave elastography (pSWE) provides noninvasive measures of mechanical stiffness of biological tissue. Over the past decade, research has demonstrated that pSWE is effective at diagnosing a multitude of pathologies such as liver fibrosis and cancer. Life science researchers stand to benefit tremendously from access to pSWE but a number of challenges have limited its use in small animals...
Radiofrequency and microwave ablation procedures are commonly used for treating hepatocellular carcinoma in patients that are not candidates for surgical resection. Ablation is a minimally invasive procedure which involves insertion of an ablation needle (electrode) into the tumor which produces localized heating to kill the surrounding cancerous cells. Ultrasound can be a valuable tool for real-time...
An effective imaging modality to delineate the ablated region after microwave ablation (MWA) therapy is crucial to yield promising treatment outcomes. Ultrasound B mode imaging is widely used to guide the ablation needle. However, the image quality suffers from relatively low imaging contrast due to the similar echogenicity between the ablated and surrounding liver tissue. In this study, we applied...
Increased myocardial stiffness is characteristic of many diseases, leads to a loss of diastolic function, and is a cause of diastolic heart failure (DHF). Methods to estimate myocardial stiffness include Shear Wave Elastography (SWE). Currently, ultrasound-based cardiac SWE includes acoustic radiation force (ARF)-based methods; however, the in vivo generation and detection of the shear waves in myocardium...
Individuals infected with the human immunodeficiency virus (HIV) are prone to develop cardiovascular disease (CVD) because the HIV infection and combination antiretroviral therapy (cART) produces atherosclerosis. Clinicians need sensitive tests to monitor interventions designed to prevent CVD in patients with HIV on long term cART. We hypothesize that vascular elastography can fulfill this role. To...
In vivo measurement of the mechanical properties of thin-walled soft tissues (e.g., mitral valve, artery and bladder) and in situ mechanical characterization of thin-walled artificial soft biomaterials in service are of great challenge. Those thin-walled structures are usually pre-stressed to achieve and/or improve their functional performance, which further complicate the inverse analysis to identify...
Diagnosis and assessment of liver fibrosis grade required for management is mainly based on blood tests and invasive hepatic puncture-biopsy. Quantitative UltraSound (QUS) techniques provide insight into tissue microstructure and are based on the frequency-based analysis of the signals from biological tissues. This study aims to explore the diagnostic performance of QUS technique in high frequency...
Investigating myocardial dynamics through the assessment of mechanical properties of heart is a challenging problem in a murine model as the heart rate is high. The objective of this study was to compare displacements estimated using radiofrequency (RF) signals with Cardiac Elastography (CE) and Speckle Tracking Echocardiography (STE) for quantifying myocardial dynamics.
Ultrasound shear wave elastography is a well established tool for characterization of biologic tissues. While it has found applications in various medical disciplines such as oncology and urology its feasibility for pneumology still has to be shown. We provide experimental results of ultrasound shear wave elastography of soft porous materials in phantoms. Shear wave dispersion and evidence of the...
Elastography plays a key role in characterizing soft tissue. Although it has found widespread use in clinical diagnostics, nearly all methods require direct physical contact with tissue and can even be invasive. However, for a number of applications (ophthalmic, for instance) physical contact is not desired and may not even be allowed. Recently, we proposed a fundamentally new approach to 4-D dynamic...
A challenge in the clinical application of shear wave elastography is the level of measurement variance or noise compared to clinically significant changes in shear wave speed. For instance, liver fibrosis staging is challenged by the relatively high variance of shear wave velocity estimates in comparison to the modulus difference between early (F1-F3) fibrosis stages. Recent work has shown that ultrasound...
When a wave field is measured within a propagative medium, it is widely accepted that the resulting image resolution depends on the measuring point density, and no longer on the wavelength. Indeed, in-situ measurements allow the near-field details needed for super-resolution to be retrieved. This is supported here by two experiments conducted in elastography. In the first, the virtual source and sink...
Atrial fibrillation and ventricular tachycardia are currently treated with catheter ablation using radiofrequency or cryoenergy. These endocardiac approaches are invasive and not fully satisfactory as the treatments are often incomplete and can be associated with side effects. HIFU were proposed as an alternative strategy, by using the excellent acoustic window between heart and esophagus. The present...
Quasi-static elastography is a widely applied ultrasound method in which RF data acquired in tissue at different states of deformation are correlated to estimate displacements and strain (displacement gradient). A recent development is the introduction of ultrafast plane-wave imaging where element data are beam-formed after collection to reconstruct the image lines. Several beam-forming strategies...
Previous studies have reported that shear wave speed along muscle fibers is distinct from the speed across the fibers. Therefore, the shear speed may be a sensitive method to determine muscle fiber orientation in vivo. The purpose of this study is to develop a reproducible method to determine anisotropy in muscle fibers using Shear Wave Elastography (SWE). This technique was used to study myofascial...
Ultrasound elastography is an effective imaging modality to delineate thermally ablated regions after ablative liver tumor treatments. The image contrast is based on the difference in the Young's modulus of local tissue. In this work, we compared our previously introduced electrode displacement elastography (EDE) with a commercially available acoustic radiation force impulse imaging (ARFI) technique,...
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