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In most studies on vascular shear wave imaging (SWI), longitudinal section is mainly concerned, and the radial motion and reflected waves are not considered in cross section. It is important to investigate the SWI in cross section when evaluating the anisotropy of the vessel wall or the complete plaque composition. In our previous study, a novel method based on coordinate transformation and directional...
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 ablated regions after microwave ablation (MWA) therapy is crucial to yield successful treatment outcomes. Ultrasound B-mode imaging is widely used to guide the ablation antenna placement. However, the image quality suffers from relatively low imaging contrast due to the similar echogenicity between the ablated and surrounding tissue. In this study, we applied...
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...
Liver fibrosis is the common result of chronic liver disease. Diagnosis and grading liver fibrosis for patient management is mainly based on blood tests and hepatic puncture-biopsy, which is particularly invasive. 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...
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...
Early detection of pathological processes is crucial for the prognosis and treatment of patients, which can be facilitated through studying tissue biomechanical properties. Shear wave elastography is a technique to estimate the shear modulus of tissue. Such measurements quantify elasticity linearized around an immediate state of local stress condition, under applied nature of excitation. Stress-strain...
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...
The potential of a fully noncontact, standoff, laserultrasound system that acquires ultrasonic images within biological tissue is examined. A pulsed laser converts optical energy into ultrasound via photoacoustic mechanisms, while laser Doppler vibrometry measures emerging ultrasonic waves at the tissue surface. Differing from photoacoustic tomography (PAT), which maps spatial variations in tissue-optical...
The pathological or physiological changes of the crystalline lens directly affect the eye accommodation and transmittance, and then increase the risk of the presbyopia and cataract for people in middle and old age groups. There is no universally accepted quantitative method to measure the lens' mechanical properties in vivo so far. This study aims to investigate the possibility of assessing the age-related...
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...
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