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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...
Noninvasive imaging of physiologic currents in the body is limited by poor spatial resolution due to the ambiguous conductivity distribution between the current sources and recording electrodes. Acoustoelectric imaging (AEI), based on the interaction between pressure and resistivity, provides higher spatial resolution. Although we have demonstrated AEI of the cardiac activation wave in the live rabbit...
Investigating biomechanical properties of the cornea can have many clinical applications, including the diagnosis of keratoconus and post-refractive keratectasia. However, ascertaining the biomechanical properties of cornea remains a challenge because of the low resolution of currently available modalities cannot provide a point-to-point stiffness mapping of cornea. In this study, we reported a high-resolution...
Echocardiography is the most used modality for the evaluation of cardiac function. To obtain a time-resolved volumetric quantification of cardiac motion, ultrafast 3-D imaging is required. Ultrafast ultrasound imaging with diverging waves has demonstrated its potential for clinical 2-D echocardiography. It has been shown that MoCo (motion compensation) strategies based on a triangle transmit arrangement...
Noninvasive electrical brain imaging in humans often suffers from poor spatial resolution due to the uncertain spread of electric fields through the head. To overcome this limitation, we propose 4D transcranial acoustoelectric brain imaging (tABI) for mapping current densities at a spatial resolution confined to the ultrasound (US) focus. Acoustoelectric (AE) imaging exploits an interaction between...
High-frequency ultrasound (>20 MHz) imaging has gained widespread attention due to its high spatial resolution being useful for basic cardiovascular and cancer research involving small animals. The sampling rate of the analog-to-digital converter in a high-frequency ultrasound system usually needs to be higher than 120-MHz to satisfy the Nyquist requirement. However, the sampling rate is typically...
Time delay estimation using cross correlation between successive RF lines is an established method to estimate tissue velocity. We have applied this method on our system using 10 MHz transducers sutured to the epicardium to measure the myocardial contraction pattern at high spatial and temporal resolution. In this setup, the myocardial tissue velocity will generally increase with the depth, as the...
Changes in microvascular structure and flow is of clinical importance in the study of a number of disease processes such as cancer and diabetes. Ultrasound is often the primary imaging procedure performed to determine appropriate treatment or surgery for testicular lesions. Currently, however, differentiation and diagnosis of both benign and malignant testicular tumours such as seminomas, leydig cell...
Super-resolution (SR) ultrasound enables detailed assessment of the fine vascular network by pinpointing individual microbubbles (MBs), using ultrasound contrast agents (UCAs). The information in SR images is determined by the density of localized MBs and their localization accuracy. To obtain high densities, one can evaluate extremely sparse subsets of MBs across thousands of frames by using a very...
Imaging of speed of sound holds great promise for medical detection and diagnosis since it is a quantitative, physical property of tissues not imaged by other means. The full Waveform Inversion (FWI) based method can build speed of sound images with high spatial resolution but it is computationally very demanding. The iterative Algebraic Reconstruction Technique (ART) is a favored choice for fast...
Spatial resolution in classic contrast-enhanced ultrasound (CEUS) is limited by acoustic diffraction. Ultrafast ultrasound localization microscopy (uULM) has enabled a sub-diffraction spatial resolution of tens of micrometers in-vivo, although at the expense of a scan duration of tens of seconds. In contrast, by exploiting the statistical properties of CEUS, super resolution optical fluctuation imaging...
In the last 10 years the advent of high frame rate ultrasound imaging has allowed the visualization and study of mechanical wave propagation in order to estimate the elastic properties of tissue. Theses waves are detected through the estimation of motion induced by the wave propagation. Despite efficient motion estimator such as speckle tracking or Tissue Doppler Imaging (TDI), the detection of mechanical...
In order to achieve better performance of bulk and surface acoustic wave resonators operating at several GHz, it is crucial to dispose of advanced techniques and methods to provide information about the elastic constants of the constituent layered materials and to image the spatial profile of the acoustic field, both inside and outside the resonator.
Tissue harmonic imaging, an essential mode of ultrasound imaging scanners, can provide images with high spatial and contrast resolutions. However, it is difficult to use this imaging mode in intravascular ultrasound (IVUS) imaging. This is so because typical IVUS transducers are operated at high frequency (>20 MHz) and have a narrow fractional bandwidth (about 50%). Due to its small aperture (about...
Multi-line transmission (MLT) is a recently developed method for high frame rate cardiac ultrasound imaging. However, a potential pitfall of this method is the presence of artifacts due to cross-talk between the MLT beams. Low complexity adaptive beamforming (LCA) is a high resolution adaptive beamforming method that chooses a weighting function out of a predefined set of apodization functions assembled...
Super-resolution ultrasound has potential for visualisation of microvasculature1. Techniques that localise isolated bubble signals first require detection algorithms to separate the bubble and tissue response. Resolution of the tortuous microvasculature requires localisations with accuracy on the micron scale. Tumour microvasculature blood velocities are <1mm/s, and even for vessel diameters approaching...
Syntethic Aperture Sequential Beamforming (SASB) has been proven to achieve a better resolution and penetration depth than Dynamic Receive Focusing (DRF). SASB has also shown great potential for use in a handheld device. SASB with a low F# (<= 0.5) has shown even better resolution at the cost of high grating lobes, which cause loss of contrast in the final image. The hypothesis is that Spatial...
In magnetomotive (MM) ultrasound (US) imaging, magnetic nanoparticle (MNP) labeled tissue is moved by a magnetically induced force. Therefore, all MNPs in the field of view are excited simultaneously and a high field strength results in magnetic saturation of MNPs, hence, in a linear response. The linear displacements are spatially resolved by US tracking methods. Recently [1], it was proposed to...
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...
Speckle tracking echocardiography (STE) is a well-established method to assess regional cardiac function. Traditionally, the left ventricular (LV) walls are divided into 18 segments (6 LV walls each with 3 segments) and the deformation parameters are measured for each of the segments. However, usually, segmental deformation curves are obtained by taking the average of an underlying strain field that...
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