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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...
Currently there are two main categories of adaptive beamforming applied to medical ultrasound imaging: minimum-variance-related beamforming(MV) and coherence-factor-related beamforming (CF), both of which have been applied to suppress side/granting lobe and clutter for plane-wave imaging. Unfortunately, due to low SNR/SINR, the resulting images may suffer from deficiencies: deteriorated speckle pattern,...
To acquire reliable medical ultrasound images and accurately detect vascular diseases, it is inevitable to improve axial resolution and contrast facilitating clearly definition of depth and thickness of blood vessel walls.
The size, distribution and morphology of microcalcifications (MCs) in breasts can for some cases be considered an early indicator of breast cancer. MCs are small, hard calcium deposits in soft breast tissue and appear as point scatterers in an ultrasound image. However, detection of MCs in ultrasound images is challenging. Background speckle often obscure the MCs and thus highly affect the probability...
The shift to software beamforming has inspired a myriad of adaptive beamformers. Some of these overestimate which signals originate from sidelobes and which originate from the mainlobe. This results in a Dark Region Artifact (DRA) next to hyperechoic targets. We investigate this artifact for seven beamformers: Delay-And-Sum (DAS), the Coherence Factor (CF), Generalized Coherence Factor (GCF), Phase...
Intravascular ultrasound (IVUS) has frequently been used by the cardiologist to diagnose atherosclerosis and guide the interventional procedures. IVUS has gained widely clinical acceptance over the past twenty years because of its superior capability to assess plaque burden and monitor artery remodeling, which also makes it as the irreplaceable image modality for most innovative multimodality intravascular...
3D Ultrasound Backscatter Tensor Imaging (3D-BTI) is a novel approach based on 3D Ultrafast Ultrasound Imaging to map fiber orientation in tissues such as the human heart in vivo [1]. Fiber orientations are obtained in entire volumes at high frame rate by computing and analyzing a voxel-wise coherence function relying on the synthetic focusing of multiple tilted plane waves. However, in rapidly moving...
After a myocardium infarction, cell loss is irremediable leading to a progressive local disorganization and change in the tissue structure altering heart function. An imaging method able to render the local tissue directivity would be a powerful tool to characterize the extent of the lesion. In this field, diffusion MRI is the reference. Because of its long acquisition time and the difficulty to tackle...
Poor quality ultrasound images and inadequate or suboptimal visualization of imaging targets is a common problem in individuals that are overweight or obese. The overweight and obese population in the United States has reached staggering proportions, with nearly 2 out of every 3 individuals overweight or obese. Despite advances in ultrasound imaging technology, techniques for these difficult-to-image...
Quality assessment of ultrasound images is difficult since image quality is subjective to the human observer. Nevertheless, image quality metrics are imperative when benchmarking different beamforming techniques. However, if we do not know how a beamformer alters an image, a quality metric might give an incorrect measurement of the image quality. Using the standard Delay-And-Sum (DAS) beamformer as...
Coherence-based methods have been shown to improve image quality by suppressing spurious lobes. However, when imaging a diffuse medium, such methods lead to a high variance of speckle amplitudes (i.e. granular appearance) which could limit their applicability for direct clinical imaging. The granular pattern may however be beneficial for speckle tracking echocardiography (STE), given the higher contrast...
The Delay-Multiply-And-Sum (DMAS) beamformer has recently been presented in the context of medical ultrasound image formation. Images obtained with the DMAS beamformer present improved contrast resolution and noise rejection when compared to images obtained with the standard Delay-And-Sum (DAS) beamformer. We study here the signal statistics for a homogeneous medium using both the DAS and DMAS beamformers...
Plane-wave imaging plays a highly significant role o wing to the special demand for high frame rate, however, its po or image quality hinders its application in ultrasound industrie s. Many scholars have attempted to give a wide variety of soluti ons to improve the image quality, however, each of them has li mitations or compromises. In this study, we improve the spatio -temporally smoothed factor...
An undesired effect, the dark region artifact (DRA), has been under-communicated in our research community. The DRA appear next to acoustically strong targets for some of the many adaptive beamformers introduced in the literature. This study investigates the DRA for a collection of adaptive beamformers and shows that this effect originates because some of the methods fail to estimate which signals...
Background speckle can often obscure objects of interest in an ultrasound image. The probability of detection and classification of point scatterers is highly affected by background speckle. The proposed algorithm uses a coherence-based wavelet coefficient shrinkage method. Point scatterers in the ultrasound image are enhanced by separating coherent point targets from incoherent background speckle...
The heart, like skeletal muscles, is made up of muscular cells arranged regularly and packed into sort of bundles commonly called cardiac fibers. After a myocardial infarction (MI) both during the acute phase and the reperfusion of the myocardium, several cells die and some local fibers orientation modifications appear. Consequently, the heart does not contract properly anymore. The evaluation of...
Adaptive beamformers aim for improved resolution and contrast in the ultrasound images, and their performance is typically benchmarked using metrics such as contrast ratio (CR) and contrast-to-noise ratio (CNR). Using synthetic aperture Field II simulations, we show that certain beamformers alter speckle statistics and that this opens up for cherry picking of contrast metrics.
As medical ultrasound (MU) signals are not stationary, the radiation pattern of the corresponding input data does not have a specific shape; thus, their reconstruction using Adaptive Beamformers (BF) becomes indispensable in order to improve the quality of the imaging system. Generalized Sidelobe Canceller (GSC) is a robust realization against clutter and interference, resulting from an elegant representation...
A multi-frame rate plane wave imaging strategy is developed to simultaneously image tumor vasculature and quantify tumor perfusion. Customised imaging sequences interleaving a short but high frame rate (HFR) plane wave imaging sequence with a long but low frame rate imaging (LFR) sequence were implemented using a programmable ultrasound research platform. The results from a spatio-temporal coherence...
In this paper, we propose the frequency domain minimum variance (MV) method plus coherence factor (CF) weighting technique to improve the axial resolution of medical ultrasound images. The minimum variance beamformer is originally proposed to apply over aperture domain data to improve lateral resolution. Via the help of spectral whitening, the MV method can be applied to the frequency components which...
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