Publications
264 results found
Mulvana H, Browning RJ, Luan Y, et al., 2017, Characterisation of Contrast Agent Microbubbles for Ultrasound Imaging and Therapy Research., IEEE Trans Ultrason Ferroelectr Freq Control
The high efficiency with which gas microbubbles can scatter ultrasound compared to the surrounding blood pool or tissues has led to their widespread employment as contrast agents in ultrasound imaging. In recent years their applications have been extended to include super-resolution imaging and the stimulation of localized bio-effects for therapy. The growing exploitation of contrast agents in ultrasound, and in particular these recent developments, have amplified the need to characterize and fully understand microbubble behavior. The aim in doing so is to more fully exploit their utility for both diagnostic imaging and potential future therapeutic applications.
Mulvana H, Browning RJ, Luan Y, et al., 2017, Characterization of Contrast Agent Microbubbles for Ultrasound Imaging and Therapy Research, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, Vol: 64, Pages: 232-251, ISSN: 0885-3010
Toulemonde M, Li Y, Lin S, et al., 2016, Cardiac imaging with high frame rate contrast enhanced ultrasound: in-vivo demonstration, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
This work presents the first in-vivo High-frame rate Contrast Enhanced Ultrasound (HFR CEUS) for cardiac application. The in-vivo acquisition has been made on a sheep. A coherent compounding of diverging waves combined with Pulse Inversion (PI) transmission allow a frame rate of 250 frame per seconds which is 8 times faster than standard CEUS acquisition in cardiac application. The proposed method improves the image contrast compared to the CEUS and allows a better tracking of fast movement of the heart.
Pouliopoulos A, Caiqin L, Tinguely M, et al., 2016, Rapid short-pulse sequences enhance the spatiotemporal uniformity of acoustically driven microbubble activity during flow conditions, Journal of the Acoustical Society of America, Vol: 140, ISSN: 0001-4966
Despite the promise of microbubble-mediated focused ultrasound therapies, in vivo findings have revealed over-treated and under-treated regions distributed throughout the focal volume. This poor distribution cannot be improved by conventional pulse shapes and sequences, due to their limited ability to control acoustic cavitation dynamics within the ultrasonic focus. This paper describes the design of a rapid short-pulse (RaSP) sequence which is comprised of short pulses separated by μs off-time intervals. Improved acoustic cavitation distribution was based on the hypothesis that microbubbles can freely move during the pulse off-times. Flowing SonoVue® microbubbles (flow velocity: 10 mm/s) were sonicated with a 0.5 MHz focused ultrasound transducer using RaSP sequences (peak-rarefactional pressures: 146–900 kPa, pulse repetition frequency: 1.25 kHz, and pulse lengths: 5–50 cycles). The distribution of cavitation activity was evaluated using passive acoustic mapping. RaSP sequences generated uniform distributions within the focus in contrast to long pulses (50 000 cycles) that produced non-uniform distributions. Fast microbubble destruction occurred for long pulses, whereas microbubble activity was sustained for longer durations for shorter pulses. High-speed microscopy revealed increased mobility in the direction of flow during RaSP sonication. In conclusion, RaSP sequences produced spatiotemporally uniform cavitation distributions and could result in efficient therapies by spreading cavitation throughout the treatment area.
Gujral DM, Cheung WK, Shah BN, et al., 2016, Contrast enhancement of carotid adventitial vasa vasorum as a biomarker of radiation-induced atherosclerosis., Radiotherapy and Oncology, ISSN: 0167-8140
PURPOSE: Abnormal proliferation of adventitial vasa vasorum (vv) occurs early at sites of atherosclerosis and is thought to be an early biomarker of vascular damage. Contrast-enhanced ultrasound (CEUS) can detect this process. Its usefulness in irradiated arteries as a measure of accelerated atherosclerosis is unknown. This study investigates contrast intensity in carotid adventitia as an early marker of radiation-induced damage in head and neck cancer (HNC) patients. MATERIALS/METHODS: Patients with HNC treated with a wedged-pair and matched neck technique or hemi-neck radiotherapy (RT) (unirradiated side as control) at least 2years previously were included. Patients had been prescribed a dose of at least 50Gy to the neck. CEUS was performed on both carotid arteries and a region of interest was selected in the adventitia of the far wall of both left and right distal common carotid arteries. Novel quantification software was used to compare the average intensity per pixel between irradiated and unirradiated arteries. RESULTS: 48 patients (34 males) with median age of 59.2years (interquartile range (IQR) 49.2-64.2) were included. The mean maximum point dose to the irradiated artery was 61.2Gy (IQR 52.6-61.8) and 1.1Gy (IQR 1.0-1.8Gy) to the unirradiated side. The median interval from RT was 59.4months (IQR 41-88.7). There was a significant difference in the mean (SD) contrast intensity per pixel on the irradiated side (1.1 (0.4)) versus 0.96 (0.34) on the unirradiated side (p=0.01). After attenuation correction, the difference in mean contrast intensity per pixel was still significant (1.4 (0.58) versus 1.2 (0.47) (p=0.02). Previous surgery or chemotherapy had no effect on the difference in contrast intensity between the 2 sides of the neck. Mean intensity per pixel did not correlate to traditional risk prediction models (carotid intima-medial thickness, QSTROKE score). CONCLUSIONS: Proliferation of vv is demonstrated by increased contrast intensity in irradiated car
Stanziola A, Toulemonde M, Yildiz YO, et al., 2016, Ultrasound Imaging with Microbubbles, IEEE Signal Processing Magazine, Vol: 33, Pages: 111-117, ISSN: 1053-5888
Li Y, Ho CP, Chahal N, et al., 2016, Myocardial segmentation of contrast echocardiograms using random forests guided by shape model, Pages: 158-165, ISSN: 0302-9743
Myocardial Contrast Echocardiography (MCE) with microbubble contrast agent enables myocardial perfusion quantification which is invaluable for the early detection of coronary artery diseases. In this paper,we proposed a new segmentation method called Shape Model guided Random Forests (SMRF) for the analysis of MCE data. The proposed method utilizes a statistical shape model of the myocardium to guide the Random Forest (RF) segmentation in two ways. First,we introduce a novel Shape Model (SM) feature which captures the global structure and shape of the myocardium to produce a more accurate RF probability map. Second,the shape model is fitted to the RF probability map to further refine and constrain the final segmentation to plausible myocardial shapes. Evaluated on clinical MCE images from 15 patients,our method obtained promising results (Dice = 0.81,Jaccard = 0.70,MAD = 1.68 mm,HD = 6.53mm) and showed a notable improvement in segmentation accuracy over the classic RF and its variants.
Theodorou M, Jaeger M, Fromageau J, et al., 2016, Single transducer LOVIT-enabled photoacoustic imaging: a feasibility study, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Lin S, Zhang G, Leow CH, et al., 2016, Vaporising Phase Change Ultrasound Contrast Agent in Microvascular Confinement, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Lee WF, Papadopoulou V, Corbett RW, et al., 2016, Automated Segmentation of Blood Vessel in Contrast Enhanced Plane Wave Ultrasound Images, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Leow C, Tang M, Bazigou E, et al., 2015, Flow velocity mapping using contrast enhanced high-frame-rate plane wave ultrasound and image tracking: methods and initial in vitro and in vivo evaluation, Ultrasound in Medicine and Biology, Vol: 41, Pages: 2913-2925, ISSN: 0301-5629
Ultrasound imaging is the most widely used method for visualising and quantifying blood flow in medical practice, but existing techniques have various limitations in terms of imaging sensitivity, field of view, flow angle dependence, and imaging depth. In this study, we developed an ultrasound imaging velocimetry approach capable of visualising and quantifying dynamic flow, by combining high-frame-rate plane wave ultrasound imaging, microbubble contrast agents, pulse inversion contrast imaging and speckle image tracking algorithms. The system was initially evaluated in vitro on both straight and carotid-mimicking vessels with steady and pulsatile flows and in vivo in the rabbit aorta. Colour and spectral Doppler measurements were also made. Initial flow mapping results were compared with theoretical prediction and reference Doppler measurements and indicate the potential of the new system as a highly sensitive, accurate, angle-independent and full field-of-view velocity mapping tool capable of tracking and quantifying fast and dynamic flows.
Yeh JS-M, Sennoga CA, McConnell E, et al., 2015, QUANTITATIVE ULTRASOUND MOLECULAR IMAGING, ULTRASOUND IN MEDICINE AND BIOLOGY, Vol: 41, Pages: 2478-2496, ISSN: 0301-5629
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- Citations: 10
Ja'afar F, Leow CH, Garbin V, et al., 2015, Surface Charge Measurement of SonoVue, Definity and Optison: A Comparison of Laser Doppler Electrophoresis and Micro-Electrophoresis, Ultrasound in Medicine and Biology, Vol: 41, Pages: 2990-3000, ISSN: 0301-5629
Microbubble (MB) contrast-enhanced ultrasonography is a promising tool for targeted molecular imaging. It is important to determine the MB surface charge accurately as it affects the MB interactions with cell membranes. In this article, we report the surface charge measurement of SonoVue, Definity and Optison. We compare the performance of the widely used laser Doppler electrophoresis with an in-house micro-electrophoresis system. By optically tracking MB electrophoretic velocity in a microchannel, we determined the zeta potentials of MB samples. Using micro-electrophoresis, we obtained zeta potential values for SonoVue, Definity and Optison of −28.3, −4.2 and −9.5 mV, with relative standard deviations of 5%, 48% and 8%, respectively. In comparison, laser Doppler electrophoresis gave −8.7, +0.7 and +15.8 mV with relative standard deviations of 330%, 29,000% and 130%, respectively. We found that the reliability of laser Doppler electrophoresis is compromised by MB buoyancy. Micro-electrophoresis determined zeta potential values with a 10-fold improvement in relative standard deviation.
leow, iori F, corbett R, et al., 2015, Microbubble void imaging – a non-invasive technique for flow visualisation and quantification of mixing in large vessels using plane wave ultrasound and controlled microbubble contrast agent destruction, Ultrasound in Medicine and Biology, Vol: 41, Pages: 2926-2937, ISSN: 0301-5629
Yeh JS-M, Sennoga CA, McConnell E, et al., 2015, A targeting microbubble for ultrasound molecular imaging, PLoS ONE, Vol: 10, ISSN: 1932-6203
Yildiz YO, Eckersley RJ, Senior R, et al., 2015, CORRECTION OF NON-LINEAR PROPAGATION ARTIFACT IN CONTRAST-ENHANCED ULTRASOUND IMAGING OF CAROTID ARTERIES: METHODS AND <i>IN VITRO</i> EVALUATION, ULTRASOUND IN MEDICINE AND BIOLOGY, Vol: 41, Pages: 1938-1947, ISSN: 0301-5629
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- Citations: 16
Li S, Cheng Y, Eckersley RJ, et al., 2015, Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement, Biomedical Optics Express, Vol: 6, Pages: 1954-1962, ISSN: 2156-7085
Shear wave speed is quantitatively related to tissue viscoelasticity.Previously we reported shear wave tracking at centimetre depths ina turbid optical medium using laser speckle contrast detection. Shear waveprogression modulates displacement of optical scatterers and therefore modulatesphoton phase and changes the laser speckle patterns. Time-resolvedcharge-coupled device (CCD)-based speckle contrast analysis was used totrack shear waves and measure the time-of-flight of shear waves for speedmeasurement. In this manuscript, we report a new observation of the laserspeckle contrast difference signal for dual shear waves. A modulation ofCCD speckle contrast difference was observed and simulation reproducesthe modulation pattern, suggesting its origin. Both experimental andsimulation results show that the dual shear wave approach generates animproved definition of temporal features in the time-of-flight optical signaland an improved signal to noise ratio with a standard deviation less than50% that of individual shear waves. Results also show that dual shear wavescan correct the bias of shear wave speed measurement caused by shear wavereflections from elastic boundaries.
Papadopoulou V, Evgenidis S, Eckersley RJ, et al., 2015, Decompression induced bubble dynamics on ex vivo fat and muscle tissue surfaces with a new experimental set up, Colloids and Surfaces B - Biointerfaces, Vol: 129, Pages: 121-129, ISSN: 1873-4367
Vascular gas bubbles are routinely observed after scuba dives using ultrasound imaging, however the precise formation mechanism and site of these bubbles are still debated and growth from decompression in vivo has not been extensively studied, due in part to imaging difficulties. An experimental set-up was developed for optical recording of bubble growth and density on tissue surface area during hyperbaric decompression. Muscle and fat tissues (rabbits, ex vivo) were covered with nitrogen saturated distilled water and decompression experiments performed, from 3 to 0 bar, at a rate of 1 bar/min. Pictures were automatically acquired every 5 s from the start of the decompression for 1 h with a resolution of 1.75 μm. A custom MatLab analysis code implementing a circular Hough transform was written and shown to be able to track bubble growth sequences including bubble center, radius, contact line and contact angles over time. Bubble density, nucleation threshold and detachment size, as well as coalescence behavior, were shown significantly different for muscle and fat tissues surfaces, whereas growth rates after a critical size were governed by diffusion as expected. Heterogeneous nucleation was observed from preferential sites on the tissue substrate, where the bubbles grow, detach and new bubbles form in turn. No new nucleation sites were observed after the first 10 min post decompression start so bubble density did not vary after this point in the experiment. In addition, a competition for dissolved gas between adjacent multiple bubbles was demonstrated in increased delay times as well as slower growth rates for non-isolated bubbles.
Li S, Lin S, Cheng Y, et al., 2015, Quantifying Activation of Perfluorocarbon-Based Phase-Change Contrast Agents Using Simultaneous Acoustic and Optical Observation, Ultrasound in Medicine and Biology, Vol: 41, Pages: 1422-1431, ISSN: 0301-5629
Christensen-Jeffries K, Browning RJ, Tang M-X, et al., 2015, In vivo acoustic super-resolution and super-resolved velocity mapping using microbubbles, IEEE Transactions on Medical Imaging, Vol: 34, Pages: 433-440, ISSN: 0278-0062
The structure of microvasculature cannot be resolved using standard clinical ultrasound (US) imaging frequencies due to the fundamental diffraction limit of US waves. In this work, we use a standard clinical US system to perform in vivo sub-diffraction imaging on a CD1, female mouse aged eight weeks by localizing isolated US signals from microbubbles flowing within the ear microvasculature, and compare our results to optical microscopy. Furthermore, we develop a new technique to map blood velocity at super-resolution by tracking individual bubbles through the vasculature. Resolution is improved from a measured lateral and axial resolution of 112 μm and 94 μm respectively in original US data, to super-resolved images of microvasculature where vessel features as fine as 19 μm are clearly visualized. Velocity maps clearly distinguish opposing flow direction and separated speed distributions in adjacent vessels, thereby enabling further differentiation between vessels otherwise not spatially separated in the image. This technique overcomes the diffraction limit to provide a noninvasive means of imaging the microvasculature at super-resolution, to depths of many centimeters. In the future, this method could noninvasively image pathological or therapeutic changes in the microvasculature at centimeter depths in vivo.
Cheng Y, Li S, Eckersley RJ, et al., 2015, Detecting tissue optical and mechanical properties with an ultrasound modulated optical imaging system in reflection detection geometry, BIOMEDICAL OPTICS EXPRESS, Vol: 6, Pages: 63-71, ISSN: 2156-7085
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- Citations: 6
Stanziola A, Cheung WK, Eckersley R, et al., 2015, MOTION CORRECTION IN CONTRAST-ENHANCED ULTRASOUND SCANS OF CAROTID ATHEROSCLEROTIC PLAQUES, IEEE 12th International Symposium on Biomedical Imaging, Publisher: IEEE, Pages: 1093-1096, ISSN: 1945-7928
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- Citations: 1
Eckersley RJ, Christensen-Jeffries K, Tang MX, et al., 2015, Super-resolution imaging of microbubble contrast agents, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Fu F, Li B, Dai M, et al., 2014, Use of electrical impedance tomography to monitor regional cerebral edema during clinical dehydration treatment, PLoS ONE, Vol: 9
©2014 Fu et al. Objective:Variations of conductive fluid content in brain tissue (e.g. cerebral edema) change tissue impedance and can potentially be measured by Electrical Impedance Tomography (EIT), an emerging medical imaging technique. The objective of this work is to establish the feasibility of using EIT as an imaging tool for monitoring brain fluid content.Design:A prospective study.Setting:In this study EIT was used, for the first time, to monitor variations in cerebral fluid content in a clinical model with patients undergoing clinical dehydration treatment. The EIT system was developed in house and its imaging sensitivity and spatial resolution were evaluated on a saline-filled tank.Patients:23 patients with brain edema.Interventions:The patients were continuously imaged by EIT for two hours after initiation of dehydration treatment using 0.5 g/kg intravenous infusion of mannitol for 20 minutes.Measurement and Main Results: Overall impedance across the brain increased significantly before and after mannitol dehydration treatment (p=0.0027). Of the all 23 patients, 14 showed high-level impedance increase and maintained this around 4 hours after the dehydration treatment whereas the other 9 also showed great impedance gain during the treatment but it gradually decreased after the treatment. Further analysis of the regions of interest in the EIT images revealed that diseased regions, identified on corresponding CT images, showed significantly less impedance changes than normal regions during the monitoring period, indicating variations in different patients' responses to such treatment.Conclusions:EIT shows potential promise as an imaging tool for real-time and non-invasive monitoring of brain edema patients.
Fu F, Li B, Dai M, et al., 2014, Use of Electrical Impedance Tomography to monitor regional cerebral edema during clinical dehydration treatment, PLoS ONE, Vol: 9, ISSN: 1932-6203
Sennoga CA, Seddon JM, Frueh JA, et al., 2014, DYNAMICS OF TARGETED MICROBUBBLE ADHESION UNDER PULSATILE COMPARED WITH STEADY FLOW, ULTRASOUND IN MEDICINE AND BIOLOGY, Vol: 40, Pages: 2445-2457, ISSN: 0301-5629
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- Citations: 1
Cheung W, Gujral DM, Shah BNA, et al., 2014, Attenuation correction and normalisation for quantification of contrast enhancement in ultrasound Images of carotid arteries, Ultrasound in Medicine and Biology, Vol: 41, Pages: 1876-1883, ISSN: 0301-5629
An automated attenuation correction and normalisation algorithm was developed to improve the quantification of contrast enhancement in ultrasound images of carotid arteries. The algorithm first corrects attenuation artefact and normalises intensity within the contrast agent-filled lumen and then extends the correction and normalisation to regions beyond the lumen. The algorithm was first validated on phantoms consisting of contrast agent-filled vessels embedded in tissue-mimicking materials of known attenuation. It was subsequently applied to invivo contrast-enhanced ultrasound (CEUS) images of human carotid arteries. Both invitro and invivo results indicated significant reduction in the shadowing artefact and improved homogeneity within the carotid lumens after the correction. The error in quantification of microbubble contrast enhancement caused by attenuation on phantoms was reduced from 55% to 5% on average. In conclusion, the proposed method exhibited great potential in reducing attenuation artefact and improving quantification in contrast-enhanced ultrasound of carotid arteries.
Papadopoulou V, Tang M-X, Balestra C, et al., 2014, Circulatory bubble dynamics: From physical to biological aspects, ADVANCES IN COLLOID AND INTERFACE SCIENCE, Vol: 206, Pages: 239-249, ISSN: 0001-8686
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- Citations: 56
Li S, Cheng Y, Song L, et al., 2014, Tracking shear waves in turbid medium by light: theory, simulation, and experiment, OPTICS LETTERS, Vol: 39, Pages: 1597-1600, ISSN: 0146-9592
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- Citations: 8
Germonpré P, Papadopoulou V, Hemelryck W, et al., 2014, The use of portable 2D echocardiography and ‘frame-based’ bubble counting as a tool to evaluate diving decompression stress, Diving and Hyperbaric Medicine, Vol: 44, Pages: 5-13, ISSN: 1833-3516
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