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Endoscopy and colonoscopy are the clinically recognised standards for imaging and diagnosis of diseases of the gastrointestinal (GI) tract. While 'scope-based approaches combine optical and ultrasound imaging to allow both imaging of the surface and full thickness of the bowel wall, they are limited in their ability to access the full length of the GI tract particularly the small bowel. Wireless video...
Histotripsy is considered a non-invasive therapeutic modality capable of mechanically fractionating tissue using cavitation bubbles induced by high intensity focused ultrasound pulses. Histotripsy-induced cavitation region over relatively large focal volume is effective in treating sizable lesion, while compromising its treatment precision. We demonstrate high-precision cavitation treatment using...
We present a new technique for photoacoustic (PA) image formation, termed ‘F-Mode’, which capitalizes on variations in the power spectrum of PA signals to produce images with object specific contrast. The technique is applied to a PA dataset by calculating the signal power spectrum at each scan location, segmenting it into discrete frequency bands, and then forming an image representing the spatial...
With the ongoing drive to integrate more functionality and processing power on the same semiconductor area, the device structures have become 3D. Such structures, like FinFETs and their successors Gate-All-Around (GAA) nanowire FETs, bring on new challenges to measure their geometry and material properties non-destructively at the nanometer scale. Photo Thermal Acoustic Imaging (PTAI) is a potential...
Photoacoustic Microscopy (PAM) offers a unique combination of high contrast from endogenous optical absorbers, and increased penetration to image microvasculature. However, images of the vasculature at increased depth are often corrupted by acoustic reverberation from superficial layers. In this paper, we present an algorithm using dictionary learning to remove the reverberant signal while preserving...
With the ongoing drive to integrate more functionality and processing power on the same semiconductor area, the device structures have become 3D. Such structures, like FinFETs and their successors GAA nanowire FETs, bring on new challenges to measure their geometry and material properties non-destructively at the nanometer scale. Photo Thermal Acoustic Imaging (PTAI) is a potential inspection method...
An optical ultrasound generator was used to perform broadband (2–35 MHz) acoustical characterisation measurements of a nanocomposite comprising carbon nanotubes (CNT) and polydimethylsiloxane (PDMS), a composite that is commonly used as optical ultrasound generator. Samples consisting of either pure PDMS or CNT-loaded PDMS were characterised to determine the influence of CNTs on the speed of sound...
Photoacoustic imaging is a hybrid imaging modality where ultrasound signal is generated when laser pulses are absorbed by tissue. Tissue-mimicking phantom is a useful tool to characterizing new imaging methods. However, there is still a lack of development of phantoms applied to hybrid modalities such as photoacoustics. SEBS gel is a translucent material and present acoustic and elastic properties...
Photoacoustic imaging is often used to visualize point-like targets, including circular cross sections of small cylindrical implants like brachytherapy seeds as well as circular cross sections of metal needles. When imaging these pointlike targets in the presence of highly echogenic structures, the resulting image will suffer due to reflection artifacts which appear as true signals in the traditional...
Ultrasound (US) is an ideal imaging modality used in medical practice: it is portable, has no known bio-effects and produces images with excellent resolution. Despite these advantages, MRI and CT are dominant modalities used for most medical imaging, while accepting much higher cost and health risks. US is acquired with hand held transducers dependent on operator applied pressure and angle plane selection...
Phase-change ultrasound contrast agents (PCCAs), have shown promises for ultrasound-mediated diagnostics and therapeutics. High-frame-rate ultrasound imaging with microbubbles significantly improved temporal resolution and contrast compared to conventional contrast-enhanced ultrasound imaging, offering opportunities to observe and better understand PCCA behavior after vaporisation. In this study,...
Optically triggered perfluorohexane nanodroplets (PFHnDs) can repeatedly vaporize and recondense, providing photoacoustic (PA) and blinking ultrasound (US) signals in response to pulsed laser irradiation. This property of PFHnDs has led to the development of various US imaging modes, including super-resolution and background-free contrast-enhanced imaging. However, to utilize the full potential of...
EUS is performed with radial imaging perpendicular to the endoscope shaft, and lateral imaging parallel to the shaft and biopsy channel. Radial imaging is preferred for some diagnostic and staging purpose because of ease of use as well as the production of a full 360-degree field of view. For operation smoothly and safety, the smaller external diameter (less than 11mm), the higher optical and ultrasonic...
To explore the extravascular space, sub-micron phase-change droplets show widespread interest in medical imaging and therapy with various modalities, such as ultrasound and photoacoustic. Existing studies (Wilson 2012, Wei 2014) on such dual-modality contrast agents have demonstrated the generation of both optical and ultrasound contrast after optical activation. However these studies did not explore...
Short-Lag Spatial Coherence (SLSC) is a beam-forming technique that was initially developed for ultrasound imaging, then applied to photoacoustic imaging with considerable improvements in contrast and signal-to-noise ratios, when compared to traditional delay-and-sum beamforming. However, these applications suffer from the lack of a well validated theory to support its implementation. We are developing...
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...
An EUS probe integrating radial electrical scanning transducer and wide-angle camera module has been fabricated and evaluated. The 8 MHz 128 elements radial ultrasound transducer, which can provide 360° high-resolution ultrasound imaging, has a less than 9.58 mm external diameter. A 128.3° wide-angle lens driving with a 5-million-pixel CMOS camera module can improve optical imaging resolution. After...
The potential of a fully noncontact, standoff, laserultrasound system that acquires ultrasonic images within biological tissue is examined. A pulsed laser converts optical energy into ultrasound via photoacoustic mechanisms, while laser Doppler vibrometry measures emerging ultrasonic waves at the tissue surface. Differing from photoacoustic tomography (PAT), which maps spatial variations in tissue-optical...
Rupture of an atherosclerotic plaque in the carotid artery is one of the main causes of stroke and stroke-induced death. Currently, to prevent this risk, endarterectomy is performed based on the stenosis grade assessed with Duplex ultrasound (US). However, plaque composition, e.g. presence of lipids and hemorrhages, is a more important factor of rupture risk than stenosis. The optical absorption of...
Photoacoustic (PA) imaging is an emerging molecular imaging modality. Image contrast, however, strongly decreases with depth due to light attenuation in tissue. Recently, PA phase-change contrast agents (PCCAs) have been proposed as alternative PA agents because the rapid expansion from droplet vaporization provides contrast orders of magnitude higher than that of conventional PA agents. Current PA...
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