The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
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...
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...
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...
To understand physiologic state in diseased liver e.g. non-alcoholic steatohepatitis, this study aims to analyze the acoustic impedance (Z) of hepatic cells using a scanning acoustic microscopy (SAM). Ultrasound scattering sources in cells, however, cause the multi-reflection and prevent from analyzing the precious value of Z although it provides the useful information of structure in cells (M. N...
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...
Focused ultrasound (US) produces clinically useful bioeffects such as hyperthermia, cavitation and radiation force. A focused US mediated targeted drug delivery (UmTDD) capsule endoscope was developed previously to explore treatment of gastrointestinal conditions such as Crohn's disease (SonoCAIT [1]). This included focused US transducers to enhance drug uptake into the bowel wall. In further development,...
Optical ultrasound sources, which generate ultrasound photoacoustically, are promising alternatives to piezoelectric or capacitive transducers. Employing pulsed excitation light, high bandwidths (up to 100 MHz) and pressures (MPa range for unfocussed sources) have been achieved with materials that combine strong optical absorption with a high thermal expansion coefficient, such as carbon nanotube...
The abnormal vasculature of tumor and the resulting abnormal microenvironment is a major barrier to optimal chemotherapeutic drug delivery. It is well known that ultrasound (US) can increase the permeability of the tumor vessel walls and enhance the accumulation of anticancer drugs. Reconstituted high density lipoproteins (rHDL) nanoparticles (NPs) allow selective delivery of anticancer agents to...
In this study, we developed an imaging device for preclinical and clinical application using photoacoustic effect. The photoacoustic effect is to make ultrasound images using light as its name illustrates. Light irradiated in a short time (nano seconds) is absorbed by the tissue, and the local pressure is generated by the thermo-elastic expansion. The photoacoustic effect is a safe method of imaging...
One of the main advantages of photoacoustic (PA) microscopy is its ability to generate high-resolution maps of vasculature due to strong endogenous absorption. In contrast the optical absorption of the gross anatomy surrounding the vasculature is negligible, and it is thus not readily imaged using PA. We have previously reported on a new imaging technique, termed Photoacoustic Radiometry (PAR), which...
All-optical ultrasound imaging, where ultrasound is generated photoacoustically and back-scattered fields are detected with optically resonant structures, has distinct advantages over conventional piezoelectric or capacitive transducers. An absence of electrical connections facilitates probe miniaturisation and confers MRI compatibility, while similar or better sensitivities and bandwidths can be...
Intravascular photoacoustic (IVPA) imaging is being developed to improve and guide treatment of atherosclerotic vulnerable plaques. While lipid has been successfully imaged, current studies have not determined how many or which optical wavelength(s) will accurately characterize atherosclerotic plaques. We leverage Monte Carlo (MC) optical modeling to determine the optimal dual-wavelength combination...
The Fabry-Perot (FP) polymer film sensor can detect ultrasound over a broadband frequency range (tens of MHz), with small element sizes (tens of microns), and high sensitivity. It has been used extensively in photoacoustic imaging as well as general ultrasound field characterisation. Although it will clearly affect the ultrasound field measurements, the directional response of the sensor has not been...
The maximum amplitude projection (MAP) technique is the gold standard for image formation in photoacoustic (PA) microscopy. While the technique provides high-resolution spatial maps of optical absorption, it neglects the abundance of information encoded in the frequency domain of the broadband PA signals. In this work, we present a new technique for PA image formation, termed ‘F-Mode’, which capitalizes...
Intravascular photoacoustic (IVPA) imaging, which combines the advantages of high ultrasonic resolution and strong optical absorption contrast, seems to be an alternative method to detect lipid pool and atherosclerotic lesion. A highly sensitive miniaturized ultrasound transducer is required for receiving of intravascular photoacoustic signals. As the core part of the transducer, lead-based piezoelectric...
Phase-change contrast agents (PCCAs) have advantageous properties in terms of smaller size, longer half-life and selective activation control compared to conventional microbubble contrast agents (MCAs), which make them ideal for ultrasound cancer imaging. [1] Acoustic signal from tumour site can be further enhanced by receptor targeted PCCAs. However there is still a lack of understanding of the behaviour...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.