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Flow velocity estimation is an important feature in ultrasound imaging. However, in conventional color Doppler imaging, only parallel flow components can be estimated, the velocity information is not simultaneously measured throughout the region of interest (ROI) due to sequential firing of the ultrasound beams, and the size of the ROI is limited under frame rate concerns. On the other hand, ultrafast...
Intrauterine growth restriction (IUGR) is an anomaly of fetal growth dynamics, which is mainly caused by alterations in the vascular remodeling of utero-placental arteries. With a prevalence of 10% of pregnancies, IUGR remains the leading cause of perinatal mortality. Doppler velocimetry is the common screening tool for IUGR but this imaging modality remains controversial. In this context, we evaluated...
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...
Rodents are used extensively in research to study disease and evaluate drugs. Preclinical imaging systems allow for non-invasive assessments of animals. High frequency ultrasound systems have emerged over the last 15 years as valuable tools for evaluating numerous diseases and organs. When compared against other anatomical imaging systems, such as MRI and CT, ultrasound is the most cost effective,...
Displacement estimation is a critical component of elastography. The measurement of sub-resolution displacements relies on high cross-correlation (CC) between repeated collinear RF acquisitions. CCs are degraded by common sources of acoustic noise, such as reverberation clutter, in addition to the displacement of scatterers within the radiation force field. CCs are also degraded spatially across the...
Multi-frequency transducers may have a number of emerging applications including multi-scale imaging, superharmonc contrast imaging and imaging-therapy applications. For imaging-therapy applications low-frequencies are typically needed for therapeutic heating or contrast agent destruction, while higher-frequencies are required for high-resolution imaging. However, development of these multi-frequency...
Harmonic imaging techniques are widely used in B-mode abdominal imaging and motion tracking in shear wave elasticity imaging (SWEI) to reduce clutter and improve data quality. Harmonic imaging can be both signal-to-noise (SNR) and penetration depth (PD) limited, resulting in decreased diagnostic utility. This work evaluates B-mode harmonic imaging and SWEI harmonic tracking data quality between imaging...
Ultrasound based carotid strain imaging (CSI) developed in our laboratory utilizes physiological deformation in response to arterial pressure variations. We have shown that strain indices are capable of quantifying vulnerability of carotid plaque, enhancing their validity as vascular biomarkers. However, a critique of CSI has been the lack of normalization of the maximum and peak-to-trough strain...
Intravascular ultrasound (IVUS) is a well-established diagnostic method that has been applied frequently for providing high-resolution images of vessel wall and atherosclerotic plaques. Side looking transducer has been employed in a catheter for delineating the structure of vessel wall and lesions. However, it is difficult to get the flow distribution in the vessel by side looking transducer as the...
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...
Ultrasound B-scan imaging systems operate under some well known resolution limits. To improve resolution, the concept of stable pulses, having bounded inverse filters, were described for lateral deconvolution (Chen and Parker, Enhanced resolution, J Med Imaging, 2016). This framework has been extended to the axial direction, enabling two-dimensional deconvolution.
In conventional ultrasonic monitoring of high intensity focused ultrasound (HIFU) treatment, it has been difficult to track the target region when the tissue to be treated deviates from the imaging plane along the elevation axis of the 1-D probe. A 2-D phased array probe providing 3-D imaging capability requires a large number of elements and it is very expensive to build a system to drive all channels...
The ability to measure perfusion rates of tissues in a non-invasive and label-free way could enable powerful diagnostic applications to peripheral vascular disease, ischemia, tumor hypoxia, ulcer characterization, and general tissue health. However, current medical techniques of measuring perfusion rates, which include contrast-enhanced ultrasound imaging, perfusion MR imaging require contrast agents...
Over the last decade, clinical studies show a strong interest for real-time 3D imaging. This calls for ultrasound probes with high-element-count 2D matrix transducer array, interfaced to an imaging system using an in-probe Application Specific Integrated Circuit (ASIC) that takes care of element selection, signal amplification, sub-array beamforming, etc. Since the ASIC is based on silicon and is...
Atherosclerosis in the carotid artery (CA) elevates the risk for cerebral events. Strain imaging has demonstrated to be a technique capable of identifying plaque composition. For strain imaging of carotid cross-sections, compound techniques have been developed to solve the poor strain estimation quality perpendicular to the ultrasound beam direction. This study assesses the performance of radial and...
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...
In the last decade the number of beamforming methods has exploded. Many innovative ideas have been proposed, but we lack the tools to compare the different techniques efficiently. The PICMUS challenge (IUS 2016, Tours) was a pioneering step that made clear that two things are required to establish a fair comparison: a common data format, and a body of methods to process that data.
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...
Carotid plaque vulnerability is difficult to characterize from B-mode ultrasound imaging alone. However, elastographic characterization of plaque mechanical properties may aid in the assessment of vulnerability. As an initial step to understand the complex wave propagation that can occur in plaques, we have developed simulation models that incorporate different shear moduli (μ) of the arterial wall,...
Fast acquisition sequences enable >200Hz 2D cardiac B-mode imaging with little compromise in image quality. Fast imaging minimizes frame to frame decorrelation, enabling radiofrequency (RF)-based tracking for enhanced signal-to-noise ratio (SNR) in motion and deformation imaging. Our objective was to compare the performance and clinical usefulness of Fast RF-based Tracking (FRFT) to the established...
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