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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...
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...
Robust detection of the smallest circulating cerebral microemboli is an efficient way of preventing cerebrovascular accidents (CVA). Transcranial Doppler ultrasound is widely considered as the most convenient system for the detection of microemboli. Standard detection used in commercial device is achieved through the whole Doppler energy spectrum where constant empirical thresholds are implemented...
Non-contrast blood perfusion imaging with ultrasound is difficult due to tissue clutter caused by patient physiological and sonographer hand motion. This motion causes spectral broadening of the tissue clutter signal, which then overlaps with the perfusion signal. To address this problem, we previously introduced an adaptive frequency and amplitude demodulation scheme to reduce the bandwidth of the...
Ultrafast plane wave microvessel imaging significantly improves ultrasound Doppler sensitivity. The rich spatiotemporal plane wave data enables robust clutter filtering based on singular value decomposition (SVD). However, due to the lack of transmit focusing, plane wave microvessel imaging is very susceptible to noise. The mid-to-deep region of the microvessel image is typically saturated by noise,...
Tissue Doppler Imaging (TDI) is an excellent tool for early detection of myocardial dysfunction, as well as for prognosis and follow-up of the myocardial function after surgical treatment. However, since it exploits the same principles of color flow imaging, TDI requires to balance frame rate with field of view. A novel TDI technique based on multiline transmission (MLT), i.e. the simultaneous transmission...
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...
While tissue-mimicking phantoms have been useful in the validation of ultrasonic equipment and image processing techniques, they are often restricted to simple vascular geometries due to limitations in fabrication techniques. To address this need, a novel technique has been employed to fabricate 3D-printed photo-curable poly(ethylene glycol) (PEG) hydrogel constructs containing complex, small-scale...
Photoacoustic (PA) imaging has been proposed for cancer treatment monitoring. Tumor oxygen saturation (sO2) should in principle be related to vascular parameters such as blood flow. In this work, in-vivo PA estimates of sO2 were compared to power Doppler (pD) measures of vascularity hours after the administration of microbubbles (MB), radiation therapy (XRT), individually or combined (MB-XRT).
Dysfunctions on the coronary circulation can lead to adverse and severe clinical outcomes, e.g., ischemic heart failure (IHF) or coronary artery disease (CAD). The evaluation of coronary vasculature is consequently of extreme importance to the diagnosis of these conditions. However, intramyocardial coronary vasculature cannot yet be imaged in-vivo in humans with current angiography techniques or transthoracic...
Power Doppler (PD) is the preferred technique for accessing weakly scattering blood cells with low-velocity flow. However, strong clutter decreases sensitivity of the blood signals, which degrades micro-vasculature imaging. Eigen-based filtering methods have been developed to separate the independent scattering sources using both spatial and slow-time statistics of echo data. We recently found that...
We have designed and implemented an ultrasonic imaging research platform that performs all signal processing including beamforming, using software on a GPU. Software-based approach on the GPU is expected to reduce the hardware complexity and offer the advantages of flexibility and rapid implementation even if there is any future change in the requirements for ultrasound imaging applications. An operating...
In a few years, ultrasound research platforms, also known as open scanners, have become a great tool for facilitating the experimental activities of ultrasound labs. An ideal platform should be easily programmed to permit the transmission of arbitrary sequences of arbitrary waveforms, the acquisition of huge amounts of raw echo-data, the visualization of the region of interest and, possibly, the real-time...
In the Western World, the high prevalence of stenotic plaques in the carotid arteries results in many strokes and transient ischemic events. In daily clinical practice, the severity of stenosis is estimated based on the maximum velocity measured before and after the stenosis using pulsed wave Doppler. However, because of the angle dependency of Doppler techniques, novel flow imaging techniques are...
Conventional 2D Doppler ultrasound is a valuable screening tool for early detection of cardiovascular disease, including aneurysm of the abdominal aorta (AA) and stenosis of the carotid artery (CA). However, vascular ultrasound screening rates remain low and vary widely among physicians, due to the need for a skilled sonographer, equipment costs and scan time. We have recently developed a low-cost...
Transcranial Doppler Ultrasound (TCD) is a non-invasive approach that has been used in both diagnosis and therapy of stroke. However, current TCD devices are highly operator dependent and a 2D sparse array transducer can help reduce the operator dependency with its improved imaging and focusing capabilities. This paper compares the potential of three aperiodic sparse array configurations: random array;...
In pulse compression using an M-sequence, the M-sequence modulated signal is transmitted and the received signal is correlated with the transmitted signal. However, the M-sequence modulated signal reflected from a moving object is Doppler-shifted. The Doppler-shifted M-sequence modulated signal cannot be correlated with the transmitted signal. Therefore, Doppler velocity estimation from a cyclic M-sequence...
A dual beam vector Doppler method was proposed (DOI: 10.1016/j.ultrasmedbio.2009.11.004), in which one beam is continuously tracked perpendicular to the flow direction, and the second one is used to perform velocity measurements with known Doppler angle. Since two consecutive transmission (TX) and reception (RX) events (one for each beam) are needed, the effective Doppler pulse repetition frequency...
Stillbirth is when a baby is born without signs of life after 28 weeks of gestation. It is estimated that 2.6 million stillbirths occurred in 2015 [Lawn et al. 2016]. Today, the fetus is examined at regular hospital checks during pregnancy, but no checks are done between these hospital visits. These antenatal tests are not always effective to prevent stillbirth [O'Neill et al. 2012]. More frequent...
The medical management of patients with continuous-flow left ventricular assist devices (LVADs) requires frequent measurement and analysis of various physiological parameters. Among the most important is blood pressure (BP), which cannot be reliably measured by the standard oscillometric method because of an impaired pulsation due to continuous flow. The objective of this work is to show the feasibility...
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