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Cardiovascular disease, including atherosclerosis and critical limb ischemia, affects millions of people worldwide. There is a clinical need to base treatment decisions on quantitative analysis of the plaque composition. However, no reliable clinical methods to quantify the mechanical properties of plaque components and detect plaque vulnerability currently exist, particularly for coronary disease...
As new flow imaging methods are actively being developed, there is a growing need to devise appropriate phantoms that can holistically assess the accuracy of the derived flow estimates. Straight-tube models simply cannot serve this purpose, nor can spinning discs that simulate tissue motion instead of flow dynamics. Anthropomorphic bifurcation models are also not ideal, because their geometry does...
Modification of dissolved gas content by nucleation of acoustic droplet vaporization (ADV) has been proposed for several therapeutic applications. Reducing dissolved oxygen could inhibit reactive oxygen species production during reperfusion of ischemic tissue, such as during coronary interventions to rescue myocardium. Localization of the effect may be achieved using intravascular ultrasound (IVUS),...
For many diseases, such as cancer, simultaneous imaging of different targets can lead to improved diagnosis, better patient prognosis, and therapy guidance/monitoring. PET-CT multiplexing can be cumbersome, costly, and involve radiation exposure. Other modalities such as fluorescent imaging lack clinical and pre-clinical relevance. Therefore, clinically relevant multiplexed imaging is of interest...
Pulse wave velocity (PWV) is a reliable index of arterial stiffness. To date, reflected pulse wave interference is still a major challenge for regional PWV estimation using ultrasound imaging methods. In this study, a high-resolution Radon transform (HRT) method is proposed to eliminate the reflected wave interferences in PWV estimation.
To facilitate the development and application of ultrasound shear wave elastography (SWE) in arteries, it is necessary to understand the nature of shear waves (SWs) propagating in pressurized anisotropic tubes embedded in softer surrounding tissues and blood. Phantom models are widely used to study SWE in tubular settings mimicking arterial geometry without yet considering anisotropy. To investigate...
Fast cardiac imaging using diverging waves (DW) is receiving much attention. Coherent compounding is important to keep spatial resolution and CNR acceptable. Two approaches have been presented in literature to do so: i) the full aperture of the probe is used and the virtual focus is moved along an arc centered at the center of the probe (ARC); ii) a sub-aperture is used and the virtual focus is linearly...
We have recently demonstrated the feasibility of vascular guided wave imaging (VGWI) in non-invasive estimation of bi-plane (i.e., longitudinal and transverse) transmural arterial Young's modulus (ELV, ETV) in tubular phantoms using phase velocity (cph) (Guo et al., ITEC 2016). In this study, we further compare the ETV estimated from the circumferential Lamb type (CLT) wave by VGWI with ETP from the...
Histotripsy uses high-pressure, microsecond-length pulses to generate cavitation microbubbles to fractionate targeted tissue. After the collapse of a cavitation cloud, remnant microbubbles can persist for a second or longer before passively dissolving. These bubbles can act as seed nuclei for subsequent cavitation events reducing treatment efficiency because the nuclei are not well distributed through...
Shear wave elastography is useful for quantitatively evaluating tissue elasticity by measuring the speed of a shear wave induced within the body by acoustic radiation force. We proposed a pushing-and-tracking sequence, coded push-pulse excitation to increase the signal-to-noise ratio (SNR) of the observed shear wave propagation without increasing measurement time and push-pulse amplitude1). In this...
A transparent transducer array is desired in backward-mode photoacoustic imaging (PAI). CMUT technology is especially suitable for this application because of its wide bandwidth and a wide selection of processing materials. We have previously demonstrated a single-element CMUT with an ITO bottom electrode for improved transparency. The device showed 40% to 70% optical transmission from 700 nm to 900...
Multiple research groups have recently innovated image recovery methods for fast pulse-echo ultrasound imaging (UI) that combine inverse scattering techniques with compressed sensing (CS). These methods alleviate the inherent tradeoff between the image quality and the image acquisition rate. The choice of the incident sound field is a crucial degree of freedom to implement the specific requirements...
Myocardial deformation imaging at a high frame rate (HFR) has the potential to gain new insights in cardiac mechanics by resolving short-lived mechanical events during the cardiac cycle. In order to achieve such high frame rate, our lab recently proposed to combine multi-line transmit with ‘anatomical imaging’ i.e. imaging only the anatomically relevant spatial domain (e.g. the myocardium). Although...
Phantoms are objects manufactured using a tissue mimicking material (TMM) and largely used to test protocols and mimic clinical environment for medical training. The TMM should reproduce at least one biological property to allow the association with clinical situation. The gel made by the copolymer styrene-ethylene/butylene-styrene (SEBS) in mineral oil previously reported by our group is a stable...
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...
In vivo estimation of attenuation coefficients is useful because of its potential for tissue characterization and relevance in accurate backscatter coefficient estimation. However, current methods based on spectral analysis for ultrasonic attenuation estimation suffer from a severe trade-off between estimation precision and spatial resolution. Recently, the regularized spectral log difference (RSLD)...
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...
Investigation of the complex intra-ventricular flow patterns in the left ventricle (LV) remains a challenge in clinical ultrasound. Echo-particle image velocimetry (ePIV) is able to estimate 2D flow from 2D images, but it is known to underestimate the high velocity flows present during the filling and ejection periods of the cardiac cycle[1], [2]. High frame rate (HFR) ultrasound imaging has been...
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...
Most chemotherapeutics (CTs) are delivered systemically, causing nausea, hair loss, fatigue and a compromised immune system. Biocompatible in situ forming implants (ISFIs) are drug delivery vehicles which are injected as a liquid before solidifying in tissues and ultimately breaking down. By dissolving CTs in an ISFI solution, they can be injected directly to the tumour site and released in a controllable...
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