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Accurate diagnosis of non-alcoholic steatohepatitis (NASH) is a critical issue in current clinical practice. Non-invasive diagnosis of NASH can be achieved by quantitative ultrasound (QUS), which requires a detailed understanding tissue-specific acoustic microstructure at cellular scale (i.e., 10 μm). Therefore, QUS methods would benefit from the knowledge of the acoustic properties of organelles...
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 shear waves in myocardium...
Photoacoustic (PA) imaging aims for the reconstruction of acoustic sources that originate in pulsed light absorption. While the speed of sound (SOS) in biological tissue is heterogeneous, standard reconstruction algorithms usually assume a constant SOS. This results in deformations of the reconstructed sources, which are referred to as aberration and can have a severe impact on the spatial resolution...
For many diseases, such as cancer, simultaneous imaging of different targets can lead to improved diagnosis, better patient prognosis, and therapy guidance/monitoring. PET-CT multiplexing can be cumbersome, costly, and involve radiation exposure. Other modalities such as fluorescent imaging lack clinical and pre-clinical relevance. Therefore, clinically relevant multiplexed imaging is of interest...
Pulse wave velocity (PWV) is a reliable index of arterial stiffness. To date, reflected pulse wave interference is still a major challenge for regional PWV estimation using ultrasound imaging methods. In this study, a high-resolution Radon transform (HRT) method is proposed to eliminate the reflected wave interferences in PWV estimation.
Ultrafast 3D Doppler imaging can provide volumetric high frame rate and high resolution mapping of the vascular anatomy and function [1]. Current approach relies on the use of matrix arrays connected to high count of electronics channel which remain complex and costly. Row Column Addressed (RCA) approaches have been proposed as a low complexity alternative to matrix probe for imaging of blood flows...
We present a new technique for photoacoustic (PA) image formation, termed ‘F-Mode’, which capitalizes on variations in the power spectrum of PA signals to produce images with object specific contrast. The technique is applied to a PA dataset by calculating the signal power spectrum at each scan location, segmenting it into discrete frequency bands, and then forming an image representing the spatial...
ARFI displacements have been shown to share an inverse relationship with shear wave speed — based estimates of tissue elasticity. In transthoracic imaging, induced shear waves have been observed during diastole, but only ARFI displacements have been accurately measured through both diastole and systole. We propose here a method for using diastolic shear wave speeds to calibrate ARFI displacement magnitudes,...
Photoacoustic Microscopy (PAM) offers a unique combination of high contrast from endogenous optical absorbers, and increased penetration to image microvasculature. However, images of the vasculature at increased depth are often corrupted by acoustic reverberation from superficial layers. In this paper, we present an algorithm using dictionary learning to remove the reverberant signal while preserving...
Stroke is commonly caused by thromboembolic events originating from a ruptured carotid plaque. Histological studies have shown that plaque rupture potential is related to plaque composition rather than degree of stenosis. The use of Acoustic Radiation Force Impulse (ARFI) ultrasound imaging has enabled assessment of carotid plaque composition and structure. In particular, a previous study has shown...
Contrast echocardiography (CE) ultrasound with microbubble contrast agents have significantly advanced our capability in assessing cardiac function. However in conventional CE techniques with line by line scanning, the frame rate is limited to tens of frames per second, making it difficult to track the fast flow within cardiac chamber. Recent research in high frame-rate (HFR) ultrasound have shown...
Oxygen microbubbles (OMBs) have recently been used as adjunct treatment for solid tumors. Indeed, their ability to relieve tumor hypoxia was shown to benefit sonodynamic and other treatment outcomes in vivo. However, OMBs are often administered via intratumoral injection, and the effect of repeated OMB injections in tumors has not been investigated. Here we report on the paradoxical finding that daily...
Pancreatic ductal adenocarcinoma (PDA) is one of the most prevalent types of cancer. Studies have shown that PDA treatment with IV administration of gemcitabine (GEM) is inhibited by excessive interstitium and connective tissue (stroma) surrounding the tumor. Ultrasound (US) irradiation combined with drug-loaded polylactic acid (PLA) microbubble contrast agents (MB) may circumvent this through targeted...
Recently, ultrafast Doppler techniques have been proposed for imaging brain and other slow flow targets. These techniques rely on synthetic focusing and the use of large ensemble lengths to separate slow-flow signal from the stationary clutter, but are susceptible to high acoustic and thermal noise. We have recently developed the short-lag angular coherence (SLAC) method, which suppresses the incoherent...
Ultrafast, high sensitivity Doppler imaging has led to the development of functional ultrasound (fUS), a novel functional imaging modality for detecting haemodynamic changes in cerebral blood vessels at high spatialtemporal resolution (∼100 μm, ∼1 ms). To allow for this blood tissue signal to be detected the skull either needs to be partially removed or thinned. To overcome this attenuation it has...
Crohn's disease is a chronic autoimmune disease of the intestinal tract affecting 700,000 people in the United States. The pathology of Crohn's disease is characterized by obstructing intestinal strictures due to inflammation, fibrosis, or a combination of both. The identification of fibrosis in intestinal strictures is critical, as the fibrotic strictures are irreversible and have to be removed surgically...
While skeletal muscle is often assumed to be structurally transversely isotropic (TI), its mechanical anisotropy is not well characterized in vivo. VisR ultrasound, a technique that provides information about the viscoelastic mechanical response of tissue, can be used for such in vivo characterization. Specifically, VisR-derived Relative Elasticity (RE) provides directionally dependent information...
Phase-change contrast agents (PCCAs) provide advantages over conventional microbubble contrast agents, including increased circulation time and the ability to extravasate from leaky tumor vasculature. Additionally, PCCAs can be vaporized into echogenic microbubbles for diagnostic ultrasound imaging. Previous studies have demonstrated that the vaporization threshold of PCCAs is higher in vivo than...
In vivo estimation of attenuation coefficients is useful because of its potential for tissue characterization and relevance in accurate backscatter coefficient estimation. However, current methods based on spectral analysis for ultrasonic attenuation estimation suffer from a severe trade-off between estimation precision and spatial resolution. Recently, the regularized spectral log difference (RSLD)...
Current liver cancer ablation methods are mainly thermal-based and inherently exhibit inconsistent tissue ablation due to irregular heat dissipation. Histotripsy is a non-thermal ultrasound (US) ablation method that fractionates tissue through the precise control of acoustic cavitation. This paper studies the feasibility and chronic effects of non-invasive histotripsy for liver cancer ablation in...
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