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Traumatic spinal cord injury (tSCI) often leads to debilitating neurological disabilities that in addition to the loss of sensory and motor capabilities, also includes other issues with the bladder, heart and respiration. Overall, tSCI results in a drastic decrease in the quality of life. Traumatic spinal cord injury causes an almost complete loss of blood flow at the site of injury (primary injury)...
Cardiac pathologies are often characterized by important changes of myocardial properties such as the myocardial stiffness, re-organization of muscle fiber structure, modification of the microcirculation flow, all of which remain challenging to assess quantitatively and non-invasively in vivo. Over the last decade, the advent of software-based systems has enabled the implementation of ultrafast ultrasound...
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...
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...
Pancreatic cancer is associated with poor clinical outcomes primarily, due to the advanced stage of disease at diagnosis. Harmonic contrast-enhanced endoscopic ultrasound has been proposed as an imaging approach for characterizing pancreatic masses. As an alternative, transabdominal subharmonic imaging has been proposed to limit invasiveness and better suppress nonlinear tissue echoes. In both of...
Pulse wave velocity and blood flow velocity are two different physiological parameters which are generally assessed using two different ultrasound sequences and processing techniques. This can be explained by the difference in term of signal intensity between the tissue and blood (approx. 40 dB). On one side, blood velocity can be estimated using Doppler, speckle tracking or transverse oscillation...
Signal from tissue will always be present within the lumen of vessels or in the heart. To image blood flow, this clutter needs to be suppressed sufficiently for the weaker blood signal to appear. As the magnitude and direction both of surrounding tissue and blood flow varies throughout the cardiac cycle, non-adaptive clutter filters will inevitably either yield dropouts or a significant tissue velocity...
Functional ultrasound (fUS) imaging is novel neuroimaging modality for brain activity based on the neurovascular coupling. This technique provides non-invasive dynamic mapping of the cerebral blood volume (CBV) variations through high-sensitivity power Doppler measurements. Complementary to CBV measurements, it would be of particular interest to extend fUS to cerebral blood flow (CBF) measurements...
In general, kidney patients often have hemodialysis three to four times a week, and need to take few hours once. Before hemodialysis, the medical staff must often measure the flow volume within the vessel for the patient. If blood flow is found to be insufficient, it denotes that the blood vessels are blocked for some reasons. However, it is a very serious event for the patient, which means that patients...
How to precisely evaluate the characteristics of glioma tumor in vivo is a challenging question for surgical resection clinically. Due to the infiltration feature of the tumor, precise resection remains challenging because of the uncertainties of surrounding vasculature. The sensitivity of flow measurement is improved by ultrafast plane-wave imaging which is capable of delineating the flow information...
Patients with chronic heart failure have reduced cardiac output and capacity for exercise-induced capillary vasodilation. Clinicians use left ventricular assist device (LVAD) therapy to improve physical function, but LVAD devices are designed to provide continuous blood flow and cannot increase blood flow in response to demand (i.e., exercise). Hence, this study investigated whether skeletal muscle...
Several challenges limit the use of Pulsed Wave (PW) Doppler to assess coronary blood flow: 1) Transit time effect causes spectral broadening in regions with high blood flow such as stenoses, leading to overestimation of maximum velocities. 2) High beam to flow angles (>60°) and out of plane components often occur, making manual positioning of the sample volume and angle correction difficult. 2D...
Contrast enhanced ultrasound (CEUS) imaging is widely used in clinic to enhance blood flow signal using microbubbles (MBs). In conventional CEUS methods such as pulse inversion (PI), amplitude modulation (AM), and pulse inversion amplitude modulation (PIAM) (Fig. 1), two pulses are excited individually in each transmission event (i.e. TX #1 and #2). Pulses in TX #2 are modified based on pulses in...
Recently, ultrafast ultrasound imaging has been proposed for many clinical applications. However, most operational frequencies of ultrafast ultrasound imaging are around 3.5 to 15 MHz. Currently, ultrafast 40 MHz high frequency ultrasound imaging has been developed in our Lab. High frequency ultrasound is a good choice for blood flow mapping because the backscattering signals from blood is increased...
Cardiac malformations develop in the first trimester of pregnancy and early detection of abnormalities is important to plan delivery and treatment. Recent reports indicate that blood flow patterns play a significant role in the development of the heart. Our aim is to investigate if vector flow imaging using blood speckle tracking can add useful information to the conventional ultrasound examination...
The main role of red blood cell (RBC) is oxygen delivery to body tissues via blood flow. When flowing blood is exposed to stasis or low shear rate (the radial gradient of velocity profile) in blood vessels, RBCs become aggregated resulting in alterations of blood viscosity affecting blood flow dynamics. Our group demonstrated that lower shear rate yielded greater aggregation and a higher PA signal...
Perinatal asphyxia, or oxygen deprivation during the birth, is believed to cause approximately 23% of newborn deaths worldwide and to lead to neurological disorders that can persist throughout the child's lifetime [1–4]. Unfortunately, FHRM is associated with false-negative and false-positive diagnoses, limiting the ability of clinicians to identify fetuses at risk of metabolic acidosis [5-9]. Ultrasound...
Recent studies suggest that the analysis of the intracardiac blood flow dynamics via vector imaging can provide relevant evaluation of cardiac dysfunction. In particular, the clinical importance of intraventricular vortex formation has been underlined. Cardiac magnetic resonance and contrast-enhanced ultrasound are commonly used. These approaches, however, cannot be integrated into routine clinical...
Left intraventricular blood flow follows a range of patterns that are mostly overlooked when using conventional ultrasound Doppler techniques. Vortices, in particular, as a blood redirection mechanism, could provide important information on a patient's cardiovascular health. They are not usually visualized, however, due to the need for 2D velocity vector visualization, and their transient nature,...
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