Imperial College London

Dr Chris Dunsby

Faculty of Natural SciencesDepartment of Physics

Professor of Biomedical Optics
 
 
 
//

Contact

 

+44 (0)20 7594 7755christopher.dunsby Website

 
 
//

Location

 

622Blackett LaboratorySouth Kensington Campus

//

Summary

 

Publications

Publication Type
Year
to

241 results found

Jones DC, Alexandrov Y, Curry N, Kumar S, Lanigan PMP, McGuinness CD, Dale MW, Twitchen DJ, Fisher D, Neil MAA, Dunsby C, French PMWet al., 2021, Multidimensional spectroscopy and imaging of defects in synthetic diamond: excitation-emission-lifetime luminescence measurements with multiexponential fitting and phasor analysis, Journal of Physics D: Applied Physics, Vol: 54, Pages: 1-13, ISSN: 0022-3727

We report the application of phasor analysis and nonlinear iterative fitting to complex spatial and spectroscopic luminescence decay data obtained from multidimensional microscopy of a CVD diamond grown on a HPHT substrate. This spectral and lifetime-resolved analysis enabled spatial mapping of variations in concentrations of nitrogen vacancy (NV) defects in both charge states and the quenching of NV− defects, as well as the identification of SiV− luminescence. These imaging and spectroscopic modalities may be important for reliable fabrication of quantum devices based on such defects in diamond, which will require well-defined and characterised quantum electronic properties.

Journal article

Jones B, McGlone ER, Fang Z, Pickford P, Corrêa IR, Oishi A, Jockers R, Inoue A, Kumar S, Görlitz F, Dunsby C, French PMW, Rutter GA, Tan TM, Tomas A, Bloom SRet al., 2021, Genetic and biased agonist-mediated reductions in β-arrestin recruitment prolong cAMP signalling at glucagon family receptors, Journal of Biological Chemistry, Vol: 296, Pages: 1-15, ISSN: 0021-9258

Receptors for the peptide hormones glucagon-like peptide-1 (GLP-1R), glucose-dependent insulinotropic polypeptide (GIPR) and glucagon (GCGR) are important regulators of insulin secretion and energy metabolism. GLP-1R agonists have been successfully deployed for the treatment of type 2 diabetes, but it has been suggested that their efficacy is limited by target receptor desensitisation and downregulation due to recruitment of β-arrestins. Indeed, recently described GLP-1R agonists with reduced β-arrestin-2 recruitment have delivered promising results in preclinical and clinical studies. We therefore aimed to determine if the same phenomenon could apply to the closely related GIPR and GCGR. In HEK293 cells depleted of both β-arrestin isoforms the duration of G protein-dependent cAMP/PKA signalling was increased in response to the endogenous ligand for each receptor. Moreover, in wild-type cells, “biased” GLP-1, GCG and GIP analogues with selective reductions in β-arrestin-2 recruitment led to reduced receptor endocytosis and increased insulin secretion over a prolonged stimulation period, although the latter effect was only seen at high agonist concentrations. Biased GCG analogues increased the duration of cAMP signalling, but this did not lead to increased glucose output from hepatocytes. Our study provides a rationale for development of GLP-1R, GIPR and GCGR agonists with reduced β-arrestin recruitment, but further work is needed to maximally exploit this strategy for therapeutic purposes.

Journal article

Sparks H, Dent L, Bakal C, Behrens A, Salbreux G, Dunsby Cet al., 2020, Dual-view oblique plane microscopy (dOPM), Biomedical Optics Express, ISSN: 2156-7085

We present a new folded dual-view oblique plane microscopy (OPM) techniquetermed dOPM that enables two orthogonal views of the sample to be obtained by translating apair of tilted mirrors in refocussing space. Using a water immersion 40× 1.15 NA primaryobjective, deconvolved image volumes of 200 nm beads were measured to have full width athalf maxima (FWHM) of 0.35±0.04 μm and 0.39±0.02 μm laterally and 0.81±0.07 μm axially.The measured z-sectioning value was 1.33±0.45 μm using light-sheet FWHM in the frames ofthe two views of 4.99±0.58 μm and 4.89±0.63 μm. To qualitatively demonstrate that the systemcan reduce shadow artefacts while providing a more isotropic resolution, a multi-cellularspheroid approximately 100 μm in diameter was imaged.

Journal article

Zhang G, Toulemonde M, Riemer K, Zhu J, Harput S, Christensen-Jeffries K, Zhu Z, Wang B, Leow CH, Weinberg P, Dunsby C, Tang MXet al., 2020, Effects of mechanical index on repeated sparse activation of nanodroplets in vivo, ISSN: 1948-5719

© 2020 IEEE. Current localization-based super-resolution ultrasound imaging requires a low concentration of flowing microbubbles to visualize microvasculature beyond the diffraction limit and acquisition is slow. Recent studies have shown that Acoustic Wave Sparsely Activated Localization Microscopy (AWSALM) using phase change nanodroplets can generate fast or even real-time super-resolution imaging. However, the optimal experimental conditions to activate the droplets for generating the super-resolution images are still unknown, especially the activation ultrasound amplitude or mechanical index (MI). The aim of this study is to investigate the effect of the activation MI on the repeated activation of decafluorobutane nanodroplets in vivo. Noninvasive ultrasound data acquisition on a rabbit kidney using the AWSALM pulse sequence was repeated for different activation MIs. It was found that the droplet activation was not observed in the rabbit kidney at an MI of 1.1. The activation of droplet started at an activation MI of 1.3. The contrast of activated droplet signals is maximized at an MI of 1.5 and decreased when the activation MI was increased above 1.5. Such understanding of the effects of activation MI could help improve droplet-base fast super-resolution imaging.

Conference paper

Harput S, Toulemonde M, Ramalli A, Christensen-Jeffries K, Boni E, Tortoli P, Dunsby C, Tang MXet al., 2020, Quantitative microvessel analysis with 3-D super-resolution ultrasound and velocity mapping, ISSN: 1948-5719

© 2020 IEEE. Medical image analysis is becoming increasingly accessible in the clinic. Computed tomography (CT) or magnetic resonance imaging (MRI) scans are usually post-processed to generate a 3-D visualization of the human body for surgical assistance or extract quantitative data to provide additional diagnostic information. Three dimensional super-resolution ultrasound (SR US) imaging can provide similar information at a micro-level without the high cost or ionising radiation. In this study, we implemented a high volumetric-rate 3-D SR US imaging with a 2-D spiral-shaped array and imaged an in vitro microvascular structure. From the 3-D SR US images clinically relevant parameters, such as microvascular flow rate, microvessel density and tortuosity, were extracted and compared with the ground truth.

Conference paper

Sparks H, Dvinskikh L, Firth J, Francis A, Harding S, Paterson C, MacLeod K, Dunsby Cet al., 2020, Development a flexible light-sheet fluorescence microscope for high-speed 3D imaging of calcium dynamics and 3D imaging of cellular microstructure, Journal of Biophotonics, Vol: 13, ISSN: 1864-063X

We report a flexible light‐sheet fluorescence microscope (LSFM) designed for studying dynamic events in cardiac tissue at high speed in 3D and the correlation of these events to cell microstructure. The system employs two illumination‐detection modes: the first uses angle‐dithering of a Gaussian light sheet combined with remote refocusing of the detection plane for video‐rate volumetric imaging; the second combines digitally‐scanned light‐sheet illumination with an axially‐swept light‐sheet waist and stage‐scanned acquisition for improved axial resolution compared to the first mode. We present a characterisation of the spatial resolution of the system in both modes. The first illumination‐detection mode achieves dual spectral‐channel imaging at 25 volumes per second with 1024 × 200 × 50 voxel volumes and is demonstrated by time‐lapse imaging of calcium dynamics in a live cardiomyocyte. The second illumination‐detection mode is demonstrated through the acquisition of a higher spatial resolution structural map of the t‐tubule network in a fixed cardiomyocyte cell.

Journal article

Fang Z, Chen S, Pickford P, Broichhagen J, Hodson DJ, Corrêa IR, Kumar S, Görlitz F, Dunsby C, French PMW, Rutter GA, Tan T, Bloom SR, Tomas A, Jones Bet al., 2020, The influence of peptide context on signaling and trafficking of glucagon-like peptide-1 receptor biased agonists, ACS Pharmacology & Translational Science, Vol: 3, Pages: 345-360, ISSN: 2575-9108

Signal bias and membrane trafficking have recently emerged as important considerations in the therapeutic targeting of the glucagon-like peptide-1 receptor (GLP-1R) in type 2 diabetes and obesity. In the present study, we have evaluated a peptide series with varying sequence homology between native GLP-1 and exendin-4, the archetypal ligands on which approved GLP-1R agonists are based. We find notable differences in agonist-mediated cyclic AMP signaling, recruitment of β-arrestins, endocytosis, and recycling, dependent both on the introduction of a His → Phe switch at position 1 and the specific midpeptide helical regions and C-termini of the two agonists. These observations were linked to insulin secretion in a beta cell model and provide insights into how ligand factors influence GLP-1R function at the cellular level.

Journal article

Lagarto JL, Nickdel MB, Kelly DJ, Price A, Nanchahal J, Dunsby C, French P, Itoh Yet al., 2020, Autofluorescence lifetime reports cartilage damage in osteoarthritis, Scientific Reports, Vol: 10, ISSN: 2045-2322

Osteoarthritis (OA) is the most common arthritis and its hallmark is degradation of articular cartilage by proteolytic enzymes leading to loss of joint function. It is challenging to monitor the status of cartilage in vivo and this study explores the use of autofluorescence lifetime (AFL) measurements to provide a label-free optical readout of cartilage degradation that could enable earlier detection and evaluation of potential therapies. We previously reported that treatment of ex vivo porcine cartilage with proteolytic enzymes resulted in decreased AFL. Here we report changes in AFL of ex vivo mouse knee joints, porcine metacarpophalangeal joints, normal human metatarsophalangeal articular tissue and human OA tibial plateau tissues measured with or without treatment using a compact single-point time resolved spectrofluorometer. Our data show that proteolytically damaged areas in porcine metacarpophalangeal joints present a reduced AFL and that inducing aggrecanases in mouse and human joints also significantly reduces AFL. Further, human cartilage from OA patients presents a significantly lower AFL compared to normal human cartilage. Our data suggest that AFL can detect areas of cartilage erosion and may potentially be utilised as a minimally-invasive diagnostic readout for early stage OA in combination with arthroscopy devices.

Journal article

Gorlitz F, Wysoczanski R, Kumar S, Lightley J, Garcia E, Alexandrov Y, Munro I, Johnson S, Kehoe M, Hollick C, Graham J, Donnelly L, Barnes P, Dunsby C, Neil MAA, French PMWet al., 2020, Towards easier, faster super-resolved microscopy, Conference on Single Molecule Spectroscopy and Superresolution Imaging XIII, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

Conference paper

Garcia E, Guo W, Kumar S, Gorlitz F, Sparks H, Alexandrov Y, Munro I, Kelly DJ, Warren S, Chennell G, Sardini A, Carling D, Thorpe P, Dunsby C, French PMWet al., 2020, FLIM, FRET and high content analysis, Symposium on Multiphoton Microscopy in the Biomedical Sciences XX held at SPIE BiOS Conference, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

Conference paper

Zhang G, Harput S, Toulemonde M, Broughton-Venner J, Zhu J, Riemer K, Christensen-Jeffries K, Brown J, Eckersley RJ, Weinberg P, Dunsby C, Tang M-Xet al., 2019, Acoustic wave sparsely-activated localization microscopy (AWSALM): in vivo fast ultrasound super-resolution imaging using nanodroplets, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 1930-1933, ISSN: 1948-5719

Current localization-based super-resolution ultrasound imaging requires a low concentration of flowing microbubbles to visualize microvasculature beyond the diffraction limit and acquisition is slow. Nanodroplets offer a promising solution as they can be sparsely activated and deactivated on-demand. In this study, acoustic wave sparsely-activated localization microscopy (AWSALM) using activation and deactivation of nanodroplets, an acoustic counterpart of photo-activated localization microscopy (PALM) which is less dependent on agent concentration and the presence of flow, is demonstrated for super-resolution imaging in deep tissues in vivo. An in vivo super-resolution image of a rabbit kidney is obtained in 1.1 seconds using AWSALM, where micro-vessels with apparent sizes far below the half-wavelength of 220 μm were visualized. This preliminary result demonstrates the feasibility of applying AWSALM for in vivo super-resolution imaging.

Conference paper

Ramuz M, Hasan A, Gruscheski L, Diakonov I, Pavlaki N, Nikolaev VO, Harding S, Dunsby C, Gorelik Jet al., 2019, A software tool for high-throughput real-time measurement of intensity-based ratio-metric FRET, Cells, Vol: 8, ISSN: 2073-4409

Förster resonance energy transfer (FRET) is increasingly used for non-invasive measurement of fluorescently tagged molecules in live cells. In this study, we have developed a freely available software tool MultiFRET, which, together with the use of a motorised microscope stage, allows multiple single cells to be studied in one experiment. MultiFRET is a Java plugin for Micro-Manager software, which provides real-time calculations of ratio-metric signals during acquisition and can simultaneously record from multiple cells in the same experiment. It can also make other custom-determined live calculations that can be easily exported to Excel at the end of the experiment. It is flexible and can work with multiple spectral acquisition channels. We validated this software by comparing the output of MultiFRET to that of a previously established and well-documented method for live ratio-metric FRET experiments and found no significant difference between the data produced with the use of the new MultiFRET and other methods. In this validation, we used several cAMP FRET sensors and cell models: i) isolated adult cardiomyocytes from transgenic mice expressing the cytosolic epac1-camps and targeted pmEpac1 and Epac1-PLN sensors, ii) isolated neonatal mouse cardiomyocytes transfected with the AKAP79-CUTie sensor, and iii) human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) transfected with the Epac-SH74 sensor. The MultiFRET plugin is an open source freely available package that can be used in a wide area of live cell imaging when live ratio-metric calculations are required.

Journal article

Corcoran D, Juskaite V, Xu Y, Gorlitz F, Alexandrov Y, Dunsby C, French P, Leitinger Bet al., 2019, DDR1 autophosphorylation is a result of aggregation into dense clusters, Scientific Reports, Vol: 9, ISSN: 2045-2322

The collagen receptor DDR1 is a receptor tyrosine kinase that promotes progression ofa wide range of human disorders. Little is known about how ligand binding triggers DDR1 kinase activity. We previously reported that collagen induces DDR1 activation through lateral dimer association and phosphorylation between dimers, a process that requires specific transmembrane association. Here we demonstrate ligand-induced DDR1 clustering by widefield and super-resolution imaging and provide evidence for a mechanism whereby DDR1 kinase activity is determined by its molecular density. Ligand binding resulted in initial DDR1 reorganisation into morphologically distinct clusters with unphosphorylated DDR1. Further compaction over time led to clusters with highly aggregated and phosphorylated DDR1. Ligand-induced DDR1 clustering was abolished by transmembrane mutations but did not require kinase activity. Our results significantly advance our understanding of the molecular events underpinning ligand-induced DDR1 kinase activity and provide an explanation for the unusually slow DDR1 activation kinetics.

Journal article

Jones DC, Kumar S, Lanigan PMP, McGuinness CD, Dale MW, Twitchen DJ, Fisher D, Martineau PM, Neil M, Dunsby C, French Pet al., 2019, Multidimensional luminescence microscope for imaging defect colour centres in diamond, Methods and Applications in Fluorescence, Vol: 8, ISSN: 2050-6120

We report a multidimensional luminescence microscope providing hyperspectral imaging and time-resolved (luminescence lifetime) imaging for the study of luminescent diamond defects. The instrument includes crossed-polariser white light transmission microscopy to reveal any birefringence that would indicate strain in the diamond lattice. We demonstrate the application of this new instrument to defects in natural and synthetic diamonds including N3, nitrogen and silicon vacancies. Hyperspectral imaging provides contrast that is not apparent in conventional intensity images and the luminescence lifetime provides further contrast.

Journal article

Harput S, Christensen-Jeffries K, Ramalli A, Brown J, Zhu J, Zhang G, Leow C, Toulemond M, Boni E, Tortoli P, Eckersley R, Dunsby C, Tang M-Xet al., 2019, 3-D super-resolution ultrasound imaging with a 2-D sparse array, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN: 0885-3010

High frame rate 3-D ultrasound imaging technologycombined with super-resolution processing method can visualize3-D microvascular structures by overcoming the diffractionlimited resolution in every spatial direction. However, 3-D superresolution ultrasound imaging using a full 2-D array requires asystem with large number of independent channels, the designof which might be impractical due to the high cost, complexity,and volume of data produced.In this study, a 2-D sparse array was designed and fabricatedwith 512 elements chosen from a density-tapered 2-D spirallayout. High frame rate volumetric imaging was performed usingtwo synchronized ULA-OP 256 research scanners. Volumetricimages were constructed by coherently compounding 9-angleplane waves acquired at a pulse repetition frequency of 4500Hz. Localization-based 3-D super-resolution images of two touching sub-wavelength tubes were generated from 6000 volumesacquired in 12 seconds. In conclusion, this work demonstratesthe feasibility of 3-D super-resolution imaging and super-resolvedvelocity mapping using a customized 2-D sparse array transducer

Journal article

Christensen-Jeffries K, Brown J, Harput S, Zhang G, Zhu J, Tang M-X, Dunsby C, Eckersley RJet al., 2019, Poisson statistical model of ultrasound super-resolution imaging acquisition time, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 66, Pages: 1246-1254, ISSN: 0885-3010

A number of acoustic super-resolution techniques have recently been developed to visualize microvascular structure and flow beyond the diffraction limit. A crucial aspect of all ultrasound (US) super-resolution (SR) methods using single microbubble localization is time-efficient detection of individual bubble signals. Due to the need for bubbles to circulate through the vasculature during acquisition, slow flows associated with the microcirculation limit the minimum acquisition time needed to obtain adequate spatial information. Here, a model is developed to investigate the combined effects of imaging parameters, bubble signal density, and vascular flow on SR image acquisition time. We find that the estimated minimum time needed for SR increases for slower blood velocities and greater resolution improvement. To improve SR from a resolution of λ/10 to λ/20 while imaging the microvasculature structure modeled here, the estimated minimum acquisition time increases by a factor of 14. The maximum useful imaging frame rate to provide new spatial information in each image is set by the bubble velocity at low blood flows (<;150 mm/s for a depth of 5 cm) and by the acoustic wave velocity at higher bubble velocities. Furthermore, the image acquisition procedure, transmit frequency, localization precision, and desired super-resolved image contrast together determine the optimal acquisition time achievable for fixed flow velocity. Exploring the effects of both system parameters and details of the target vasculature can allow a better choice of acquisition settings and provide improved understanding of the completeness of SR information.

Journal article

Lagarto J, Dyer B, Dunsby C, Peters N, French P, Dunsby C, Lyon Aet al., 2019, In vivo label-free optical monitoring of structural and metabolic remodeling of myocardium following infarction, Biomedical Optics Express, Vol: 10, Pages: 3506-3521, ISSN: 2156-7085

Cardiac remodeling following myocardial infarction (MI) involves structural and functional alterations in the infarcted and remote viable myocardium that can ultimately lead to heart failure. The underlying mechanisms are not fully understood and, following our previous study of the autofluorescence lifetime and diffuse reflectance signatures of the myocardium in vivo at 16 weeks post MI in rats [Biomed. Opt. Express 6(2), 324 (2015)], we here present data obtained at 1, 2 and 4 weeks post myocardial infarction that help follow the temporal progression of these changes. Our results demonstrate that both structural and metabolic changes in the heart can be monitored from the earliest time points following MI using label-free optical readouts, not only in the region of infarction but also in the remote non-infarcted myocardium. Changes in the autofluorescence intensity and lifetime parameters associated with collagen type I autofluorescence were indicative of progressive collagen deposition in tissue that was most pronounced at earlier time points and in the region of infarction. In addition to significant collagen deposition in infarcted and non-infarcted myocardium, we also report changes in the autofluorescence parameters associated with reduced nicotinamide adenine (phosphate) dinucleotide (NAD(P)H) and flavin adenine dinucleotide (FAD), which we associate with metabolic alterations throughout the heart. Parallel measurements of the diffuse reflectance spectra indicated an increased contribution of reduced cytochrome c. Our findings suggest that combining time-resolved spectrofluorometry and diffuse reflectance spectroscopy could provide a useful means to monitor cardiac function in vivo at the time of surgery.

Journal article

Zhu J, Rowland E, Harput S, Riemer K, Leow CH, Clark B, Cox K, Lim A, Christensen-Jeffries K, Zhang G, Brown J, Dunsby C, Eckersley R, Weinberg P, Tang Met al., 2019, 3D super-resolution ultrasound imaging of rabbit lymph node vasculature in vivo using microbubbles, Radiology, Vol: 291, Pages: 642-650, ISSN: 0033-8419

Background: Variations in lymph node (LN) microcirculation can be indicative of metastasis. Identifying and quantifying metastatic LNs remains essential for prognosis and treatment planning but a reliable non-invasive imaging technique is lacking. 3D super-resolution (SR) ultrasound has shown potential to noninvasively visualize microvascular networks in vivo.Purpose: To study the feasibility of 3D SR ultrasound imaging of rabbit lymph node (LN) microvascular structure and blood flow using microbubbles.Materials and Methods: In vivo studies were carried out to image popliteal LNs of two healthy male New Zealand White rabbits aged 6-8 weeks. 3D high frame rate contrast enhanced ultrasound was achieved by mechanically scanning a linear imaging probe. Individual microbubbles were identified, localized, and tracked to form 3D SR images and super-resolved velocity maps. Acoustic sub-aperture processing (ASAP)was used to improve image contrast and generateenhanced power Doppler (PD) and color Doppler (CD) images. Vessel size and blood flow velocity distributions were evaluated and assessed by Student’s paired t-test. Results:SR images revealed micro-vessels in the rabbitLN, with branches clearly resolved when separated by 30 μm, which is less than half of the acoustic wavelength and not resolvable by power or color Doppler. The apparent size distribution of most vessels in the SR images was below 80 μm and agrees with micro-CT data whereas most of those detected by Doppler techniques were larger than 80 μm. The blood flow velocity distribution indicated that most of the blood flow in the rabbit popliteal LN was at velocities lower than 5mm/s. Conclusion: 3D super-resolution ultrasound imaging using microbubbles allows non-invasive and non-ionizing visualization and quantification of rabbit lymph node microvascular structures and blood flow dynamics with resolution below the wave diffraction limit.

Journal article

Guo W, Kumar S, Gorlitz F, garcia EC, Alexandrov Y, Munro I, Kelly D, Warren S, Thorpe P, Dunsby C, French Pet al., 2019, Automated fluorescence lifetime imaging high content analysis of Förster resonance energy transfer between endogenously-labeled kinetochore proteins in live budding yeast cells, Slas Technology, Vol: 24, Pages: 308-320, ISSN: 2472-6303

We describe an open-source automated multiwell plate fluorescence lifetime imaging (FLIM) methodology to read out Förster resonance energy transfer (FRET) between fluorescent proteins (FPs) labeling endogenous kinetochore proteins (KPs) in live budding yeast cells. The low copy number of many KPs and their small spatial extent present significant challenges for the quantification of donor fluorescence lifetime in the presence of significant cellular autofluorescence and photobleaching. Automated FLIM data acquisition was controlled by µManager and incorporated wide-field time-gated imaging with optical sectioning to reduce background fluorescence. For data analysis, we used custom MATLAB-based software tools to perform kinetochore foci segmentation and local cellular background subtraction and fitted the fluorescence lifetime data using the open-source FLIMfit software. We validated the methodology using endogenous KPs labeled with mTurquoise2 FP and/or yellow FP and measured the donor fluorescence lifetimes for foci comprising 32 kinetochores with KP copy numbers as low as ~2 per kinetochore under an average labeling efficiency of 50%. We observed changes of median donor lifetime ≥250 ps for KPs known to form dimers. Thus, this FLIM high-content analysis platform enables the screening of relatively low-copy-number endogenous protein–protein interactions at spatially confined macromolecular complexes.

Journal article

Zhang G, Harput S, Hu H, Christensen-Jeffries K, Zhu J, Brown J, Leow CH, Eckersley R, Dunsby C, Tang M-Xet al., 2019, Fast acoustic wave sparsely activated localization microscopy (fast-AWSALM): ultrasound super-resolution using plane-wave activation of nanodroplets, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 66, Pages: 1039-1046, ISSN: 0885-3010

Localization-based ultrasound super-resolution imaging using microbubble contrast agents and phase-change nano-droplets has been developed to visualize microvascular structures beyond the diffraction limit. However, the long data acquisition time makes the clinical translation more challenging. In this study, fast acoustic wave sparsely activated localization microscopy (fast-AWSALM) was developed to achieve super-resolved frames with sub-second temporal resolution, by using low-boiling-point octafluoropropane nanodroplets and high frame rate plane waves for activation, destruction, as well as imaging. Fast-AWSALM was demonstrated on an in vitro microvascular phantom to super-resolve structures that could not be resolved by conventional B-mode imaging. The effects of the temperature and mechanical index on fast-AWSALM was investigated. Experimental results show that sub-wavelength micro-structures as small as 190 lm were resolvable in 200 ms with plane-wave transmission at a center frequency of 3.5 MHz and a pulse repetition frequency of 5000 Hz. This is about a 3.5 fold reduction in point spread function full-width-half-maximum compared to that measured in conventional B-mode, and two orders of magnitude faster than the recently reported AWSALM under a non-flow/very slow flow situations and other localization based methods. Just as in AWSALM, fast-AWSALM does not require flow, as is required by current microbubble based ultrasound super resolution techniques. In conclusion, this study shows the promise of fast-AWSALM, a super-resolution ultrasound technique using nanodroplets, which can generate super-resolution images in milli-seconds and does not require flow.

Journal article

Brown J, Christensen-Jeffries K, Harput S, Zhang G, Zhu J, Dunsby C, Tang M-X, Eckersley RJet al., 2019, Investigation of microbubble detection methods for super-resolution imaging of microvasculature, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 66, Pages: 676-691, ISSN: 0885-3010

Ultrasound super-resolution techniques use the response of microbubble contrast agents (MBs) to visualize the microvasculature. Techniques that localize isolated bubble signals first require detection algorithms to separate the MB and tissue responses. This work explores the three main MB detection techniques for super-resolution of microvasculature. Pulse inversion (PI), differential imaging (DI) and singular value decomposition (SVD) filtering were compared in terms of the localization accuracy, precision and contrast to tissue ratio (CTR). MB responses were simulated based on the properties of Sonovue™ and using the Marmottant model. Non-linear propagation through tissue was modelled using the k-Wave software package. For the parameters studied, the results show that PI is most appropriate for low frequency applications, but also most dependent on transducer bandwidth. SVD is preferable for high frequency acquisition where localization precision on the order of a few microns is possible. PI is largely independent of flow direction and speed compared to SVD and DI, so is appropriate for visualizing the slowest flows and tortuous vasculature. SVD is unsuitable for stationary MBs and can introduce a localization error on the order of hundreds of microns over the speed range 0- 2 mm/s and flow directions from lateral (parallel to probe) to axial (perpendicular to probe). DI is only suitable for flow rates > 0.5 mm/s or as flow becomes more axial. Overall, this study develops a MB and tissue non-linear simulation platform to improve understanding of how different MB detection techniques can impact the super-resolution process and explores some of the factors influencing the suitability of each.

Journal article

Harput S, Christensen-Jeffries K, Ramalli A, Brown J, Zhu J, Zhang G, Leow CH, Toulemonde M, Boni E, Tortoli P, Eckersley RJ, Dunsby C, Tang M-Xet al., 2019, 3-D super-resolution ultrasound (SR-US) imaging with a 2-D sparse array

High frame rate 3-D ultrasound imaging technology combined withsuper-resolution processing method can visualize 3-D microvascular structuresby overcoming the diffraction limited resolution in every spatial direction.However, 3-D super-resolution ultrasound imaging using a full 2-D arrayrequires a system with large number of independent channels, the design ofwhich might be impractical due to the high cost, complexity, and volume of dataproduced. In this study, a 2-D sparse array was designed and fabricated with 512elements chosen from a density-tapered 2-D spiral layout. High frame ratevolumetric imaging was performed using two synchronized ULA-OP 256 researchscanners. Volumetric images were constructed by coherently compounding 9-angleplane waves acquired in 3 milliseconds at a pulse repetition frequency of 3000Hz. To allow microbubbles sufficient time to move between consequent compoundedvolumetric frames, a 7-millisecond delay was introduced after each volumeacquisition. This reduced the effective volume acquisition speed to 100 Hz andthe total acquired data size by 3.3-fold. Localization-based 3-Dsuper-resolution images of two touching sub-wavelength tubes were generatedfrom 6000 volumes acquired in 60 seconds. In conclusion, this work demonstratesthe feasibility of 3D super-resolution imaging and super-resolved velocitymapping using a customized 2D sparse array transducer.

Working paper

Munro I, Garcia EAC, Yan M, Guldbrand S, Kumar S, Kwakwa K, Dunsby C, Neil M, French Pet al., 2019, Accelerating single molecule localisation microscopy through parallel processing on a high-performance computing cluster, Journal of Microscopy, Vol: 273, Pages: 148-160, ISSN: 1365-2818

Super‐resolved microscopy techniques have revolutionized the ability to study biological structures below the diffraction limit. Single molecule localization microscopy (SMLM) techniques are widely used because they are relatively straightforward to implement and can be realized at relatively low cost, e.g. compared to laser scanning microscopy techniques. However, while the data analysis can be readily undertaken using open source or other software tools, large SMLM data volumes and the complexity of the algorithms used often lead to long image data processing times that can hinder the iterative optimization of experiments. There is increasing interest in high throughput SMLM, but its further development and application is inhibited by the data processing challenges. We present here a widely applicable approach to accelerating SMLM data processing via a parallelized implementation of ThunderSTORM on a high‐performance computing (HPC) cluster and quantify the speed advantage for a four‐node cluster (with 24 cores and 128 GB RAM per node) compared to a high specification (28 cores, 128 GB RAM, SSD‐enabled) desktop workstation. This data processing speed can be readily scaled by accessing more HPC resources. Our approach is not specific to ThunderSTORM and can be adapted for a wide range of SMLM software.

Journal article

Harput S, Zhang G, Toulemonde M, Zhu J, Christensen-Jeffries K, Brown J, Eckersley RJ, Dunsby C, Tang M-Xet al., 2019, Activation and 3D Imaging of Phase-change Nanodroplet Contrast Agents with a 2D Ultrasound Probe, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 2275-2278, ISSN: 1948-5719

Conference paper

Zhang G, Harput S, Shah A, Hernandez-Gil J, Zhu J, Christensen-Jeffries K, Brown J, Long NJ, Eckersley RJ, Dunsby C, Bamber J, Tang M-Xet al., 2019, Photoacoustic Super-Resolution Imaging using Laser Activation of Low-Boiling-Point Dye-Coated Nanodroplets in vitro and in vivo, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 944-947, ISSN: 1948-5719

Conference paper

Zhang G, Harput S, Zhu J, Christensen-Jeffries K, Brown J, Leow CH, Dunsby C, Eckersley RJ, Tang M-Xet al., 2019, Minimization of Nanodroplet Activation Time using Focused-Pulses for Droplet-Based Ultrasound Super-Resolution Imaging, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 372-375, ISSN: 1948-5719

Conference paper

Harput S, Fong LH, Stanziola A, Zhang G, Toulemonde M, Zhu J, Christensen-Jeffries K, Brown J, Eckersley RJ, Grisan E, Dunsby C, Tang M-Xet al., 2019, Super-Resolution Ultrasound Image Filtering with Machine-Learning to Reduce the Localization Error, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, Pages: 2118-2121, ISSN: 1948-5719

Conference paper

Gorlitz F, Lightley J, Kumar S, Garcia E, Yan M, Wysoczanski R, Alexandrov Y, Baker JR, Barnes PJ, Munro I, Donnelly LE, Dunsby C, Neil MAA, French PMWet al., 2019, Automated multiwell plate STORM: towards open source super-resolved high content analysis, Conference on Advances in Microscopic Imaging II, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

Conference paper

Brown J, Kolas S, Christensen-Jeffries K, De Menczes C, Harput S, Zhu J, Zhang G, Tang M-X, Dunsby C, Eckersley RJet al., 2018, Development of Simultaneous Optical Imaging and Super-Resolution Ultrasound to Improve Microbubble Localization Accuracy, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719

Conference paper

Zhang G, Harput S, Hu H, Christensen-Jeffries K, Zhu J, Brown J, Leow CH, Dunsby C, Eckersley RJ, Tang M-Xet al., 2018, Fast Acoustic Wave Sparsely Activated Localization Microscopy (fast-AWSALM) using Octafluoropropane Nanodroplets, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719

Conference paper

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: respub-action=search.html&id=00321238&limit=30&person=true