377 results found
He C, Chang J, Hu Q, et al., 2019, Complex vectorial optics through gradient index lens cascades, Nature Communications, Vol: 10, ISSN: 2041-1723
Graded index (GRIN) lenses are commonly used for compact imaging systems. It is not widely appreciated that the ion-exchange process that creates the rotationally symmetric GRIN lens index profile also causes a symmetric birefringence variation. This property is usually considered a nuisance, such that manufacturing processes are optimized to keep it to a minimum. Here, rather than avoiding this birefringence, we understand and harness it by using GRIN lenses in cascade with other optical components to enable extra functionality in commonplace GRIN lens systems. We show how birefringence in the GRIN cascades can generate vector vortex beams and foci, and how it can be used advantageously to improve axial resolution. Through using the birefringence for analysis, we show that the GRIN cascades form the basis of a new single-shot Müller matrix polarimeter with potential for endoscopic label-free cancer diagnostics. The versatility of these cascades opens up new technological directions.
Chabloz N, Wenzel M, Perry H, et al., 2019, Polyfunctionalised nanoparticles bearing robust gadolinium surface units for high relaxivity performance in MRI, Chemistry - A European Journal, ISSN: 0947-6539
The first example of an octadentate gadolinium unit based on DO3A (hydration number q = 1) with a dithiocarbamate tether has been designed and attached to the surface of gold nanoparticles (around 4.4 nm in diameter). In addition to the superior robustness of this attachment, the restricted rotation of the Gd complex on the nanoparticle surface leads to a dramatic increase in relaxivity (r1) from 4.0 mM‐1 s‐1 in unbound form to 34.3 mM‐1 s‐1 (at 10 MHz, 37 °C) and 22 ± 2 mM‐1s‐1 (at 63.87 MHz, 25 °C) when immobilised on the surface. The ‘one‐pot’ synthetic route provides a straightforward and versatile way of preparing a range of multifunctional gold nanoparticles. The incorporation of additional surface units improving biocompatibility (PEG and thioglucose units) and targeting (folic acid) lead to little detrimental effect on the high relaxivity observed for these non‐toxic multifunctional materials. In addition to the passive targeting attributed to gold nanoparticles, the inclusion of a unit capable of targeting the folate receptors overexpressed by cancer cells, such as HeLa cells, illustrates the potential of these assemblies.
Brunckhorst O, Ong QJ, Elson D, et al., 2019, Novel real-time optical imaging modalities for the detection of neoplastic lesions in urology: a systematic review, Surgical Endoscopy, Vol: 33, Pages: 1349-1367, ISSN: 0930-2794
Background Current optical diagnostic techniques for malignancies are limited in their diagnostic accuracy and lack theability to further characterise disease, leading to the rapidly increasing development of novel imaging methods within urology. This systematic review critically appraises the literature for novel imagining modalities, in the detection and staging ofurological cancer and assesses their effectiveness via their utility and accuracy.Methods A systematic literature search utilising MEDLINE, EMBASE and Cochrane Library Database was conducted from1970 to September 2018 by two independent reviewers. Studies were included if they assessed real-time imaging modalities not already approved in guidelines, in vivo and in humans. Outcome measures included diagnostic accuracy and utilityparameters, including feasibility and cost.Results Of 5475 articles identified from screening, a final 46 were included. Imaging modalities for bladder cancer includedoptical coherence tomography (OCT), confocal laser endomicroscopy, autofluorescence and spectroscopic techniques. OCTwas the most widely investigated, with 12 studies demonstrating improvements in overall diagnostic accuracy (sensitivity74.5–100% and specificity 60–98.5%). Upper urinary tract malignancy diagnosis was assessed using photodynamic diagnosis(PDD), narrow band imaging, optical coherence tomography and confocal laser endomicroscopy. Only PDD demonstratedconsistent improvements in overall diagnostic accuracy in five trials (sensitivity 94–96% and specificity 96.6–100%). Limitedevidence for optical coherence tomography in percutaneous renal biopsy was identified, with anecdotal evidence for anymodality in penile cancer.Conclusions Evidence supporting the efficacy for identified novel imaging modalities remains limited at present. However,OCT for bladder cancer and PDD in upper tract malignancy demonstrate the best potential for improvement in overall diagnostic accuracy. OCT may addit
Adshead J, Oldfield F, Hadaschik B, et al., 2019, A pelvic phantom and porcine model study to evaluate the usability and technical feasibility of a tethered laparoscopic gamma probe for radioguided surgery in prostate cancer, Annual Meeting of the Society-of-Nuclear-Medicine-and-Molecular-Imaging (SNMMI), Publisher: SOC NUCLEAR MEDICINE INC, ISSN: 0161-5505
Qi J, Elson D, Stoyanov D, An eigen value calibration method and optimization for 3×3 Mueller polarimeters, 3rd China Symposium on Polarimetry and Ellipsometry
Lin J, Walsted ES, Backer V, et al., 2019, Quantification and analysis of laryngeal closure from endoscopic videos, IEEE Transactions on Biomedical Engineering, Vol: 66, Pages: 1127-1136, ISSN: 0018-9294
Objective: At present, there are no objective techniques to quantify and describe laryngeal obstruction, and the reproducibility of subjective manual quantification methods is insufficient, resulting in diagnostic inaccuracy and a poor signal-to-noise ratio in medical research. In this work, a workflow is proposed to quantify laryngeal movements from laryngoscopic videos, to facilitate the diagnosis procedure. Methods: The proposed method analyses laryngoscopic videos, and delineates glottic opening, vocal folds, and supraglottic structures, using a convolutional neural networks (CNNs) based algorithm. The segmentation is divided into two steps: A bounding box which indicates the region of interest (RoI) is found, followed by segmentation using fully convolutional networks (FCNs). The segmentation results are statistically quantified along the temporal dimension and processed using singular spectrum analysis (SSA), to extract clear objective information that can be used by the clinicians in diagnosis. Results: The segmentation was validated on 400 images from 20 videos acquired using different endoscopic systems from different patients. The results indicated significant improvements over using FCN only in terms of both processing speed (16 FPS vs. 8 FPS) and segmentation result statistics. Five clinical cases on patients have also been provided to showcase the quantitative analysis results using the proposed method. Conclusion: The proposed method guarantees a robust and fast processing of laryngoscopic videos. Measurements of glottic angles and supraglottic index showed distinctive patterns in the provided clinical cases. Significance: The proposed automated and objective method extracts important temporal laryngeal movement information, which can be used to aid laryngeal closure diagnosis.
Sheng W, Li W, Qi J, et al., 2019, Quantitative analysis of 4 x 4 Mueller matrix transformation parameters for biomedical imaging, Photonics, Vol: 6, ISSN: 2304-6732
Mueller matrix polarimetry is a potentially powerful technique for obtaining microstructural information of biomedical specimens. Thus, it has found increasing application in both backscattering imaging of bulk tissue samples and transmission microscopic imaging of thin tissue slices. Recently, we proposed a technique to transform the 4 × 4 Mueller matrix elements into a group of parameters, which have explicit associations with specific microstructural features of samples. In this paper, we thoroughly analyze the relationships between the Mueller matrix transformation parameters and the characteristic microstructures of tissues by using experimental phantoms and Monte Carlo simulations based on different tissue mimicking models. We also adopt quantitative evaluation indicators to compare the Mueller matrix transformation parameters with the Mueller matrix polar decomposition parameters. The preliminary imaging results of bulk porcine colon tissues and thin human pathological tissue slices demonstrate the potential of Mueller matrix transformation parameters as biomedical diagnostic indicators. Also, this study provides quantitative criteria for parameter selection in biomedical Mueller matrix imaging.
Li Q, Lin J, Clancy NT, et al., 2019, Estimation of tissue oxygen saturation from RGB images and sparse hyperspectral signals based on conditional generative adversarial network, International Journal of Computer Assisted Radiology and Surgery, ISSN: 1861-6410
Purpose: Intra-operative measurement of tissue oxygen saturation (StO 2 ) is important in detection of ischaemia, monitoring perfusion and identifying disease. Hyperspectral imaging (HSI) measures the optical reflectance spectrum of the tissue and uses this information to quantify its composition, including StO 2 . However, real-time monitoring is difficult due to capture rate and data processing time. Methods: An endoscopic system based on a multi-fibre probe was previously developed to sparsely capture HSI data (sHSI). These were combined with RGB images, via a deep neural network, to generate high-resolution hypercubes and calculate StO 2 . To improve accuracy and processing speed, we propose a dual-input conditional generative adversarial network, Dual2StO2, to directly estimate StO 2 by fusing features from both RGB and sHSI. Results: Validation experiments were carried out on in vivo porcine bowel data, where the ground truth StO 2 was generated from the HSI camera. Performance was also compared to our previous super-spectral-resolution network, SSRNet in terms of mean StO 2 prediction accuracy and structural similarity metrics. Dual2StO2 was also tested using simulated probe data with varying fibre number. Conclusions: StO 2 estimation by Dual2StO2 is visually closer to ground truth in general structure and achieves higher prediction accuracy and faster processing speed than SSRNet. Simulations showed that results improved when a greater number of fibres are used in the probe. Future work will include refinement of the network architecture, hardware optimization based on simulation results, and evaluation of the technique in clinical applications beyond StO 2 estimation.
Singh M, Nabavi E, Zhou Y, et al., 2019, Laparoscopic fluorescence image-guided photothermal therapy enhances cancer diagnosis and treatment, Nanotheranostics, Vol: 3, Pages: 89-102, ISSN: 2206-7418
Endoscopy is the gold standard investigation in the diagnosis of gastrointestinal cancers and the management of early and pre-malignant lesions either by resection or ablation. Recently gold nanoparticles have shown promise in cancer diagnosis and therapeutics (theranostics). The combination of multifunctional gold nanoparticles with near infrared fluorescence endoscopy for accurate mapping of early or pre-malignant lesions can potentially enhance diagnostic efficiency while precisely directing endoscopic near infrared photothermal therapy for established cancers. The integration of endoscopy with near infrared fluorescence imaging and photothermal therapy was aided by the accumulation of our multifunctionalized PEG-GNR-Cy5.5-anti-EGFR-antibody gold nanorods within gastrointestinal tumor xenografts in BALB/c mice. Control mice (with tumors) received either gold nanorods or photothermal therapy, while study mice received both treatment modalities. Local (tumor-centric) and systemic effects were examined for 30 days. Clear endoscopic near infrared fluorescence signals were observed emanating specifically from tumor sites and these corresponded precisely to the tumor margins. Endoscopic fluorescence-guided near infrared photothermal therapy successfully induced tumor ablations in all 20 mice studied, with complete histological clearance and minimal collateral damage. Multi-source analysis from histology, electron microscopy, mass spectrometry, blood, clinical evaluation, psychosocial and weight monitoring demonstrated the inherent safety of this technology. The combination of this innovative nanotechnology with gold standard clinical practice will be of value in enhancing the early optical detection of gastrointestinal cancers and a useful adjunct for its therapy.
Waldock WJ, Avila-Rencoret FB, Tincknell LG, et al., 2018, Augmented intraoperative surgical vision for the assessment of gastrointestinal cancer resection margins, 21st Annual Meeting of the Association of Upper Gastrointestinal Surgeons of Great Britain and Ireland (AUGIS), Publisher: Wiley, Pages: 15-16, ISSN: 1365-2168
Medical robotics encompasses surgical, therapeutic and rehabilitative devices that are changing medicine and healthcare. Although the field of medical robotics predates Intuitive’s da Vinci by more than a decade, it was the clinical and commercial achievements of that system that brought medical robotics to widespread patient and public attention. It is now more than 15 years since the robot began to be used for laparoscopic prostatectomy.1 Since then, research in the field has advanced tremendously due to various technological breakthroughs. Over the last few years, there has been a surge in commercial activities in medical robotics, led both by traditional medical device and technology companies as well as new start-ups. This special issue has been commissioned to capture some of the latest research being carried out by these multidisciplinary bioengineering teams and to showcase how some of these advances can impact clinical care.
Walsted ES, Lin J, Elson DS, et al., 2018, Objective quantification and analysis of laryngeal obstruction using deep learning algorithms, 28th International Congress of the European-Respiratory-Society (ERS), Publisher: EUROPEAN RESPIRATORY SOC JOURNALS LTD, ISSN: 0903-1936
Zhao T, Deng L, Wang W, et al., 2018, Bayes' theorem-based binary algorithm for fast reference-less calibration of a multimode fiber, Optics Express, Vol: 26, Pages: 20368-20378, ISSN: 1094-4087
In this paper, we present a Bayes’ theorem-based high-speed algorithm, to measure the binary transmission matrix of a multimode fiber using a digital micromirror device, in a reference-less multimode fiber imaging system. Based on conditional probability, we define a preset threshold to locate those digital-micromirror-device pixels that can be switched ‘ON’ to form a focused spot at the output. This leads to a binary transmission matrix consisting of ‘0’ and ‘1’ elements. High-enhancement-factor light focusing and raster-scanning at the distal end of the fiber are demonstrated experimentally. The key advantage of our algorithm is its capability for fast calibration of a MMF to form a tightly focused spot. In our experiment, for 5000 input-output pairs, we only need 0.26 s to calibrate one row of the transmission matrix to achieve a focused spot with an enhancement factor of 28. This is more than 10 times faster than the prVBEM algorithm. The proposed Bayes’ theorem-based binary algorithm can be applied not only in multimode optical fiber focusing but also to other disordered media. Particularly, it will be valuable in fast multimode fiber calibration for endoscopic imaging.
Saso S, Tziraki M, Clancy NT, et al., 2018, Use of Laser Speckle Contrast Analysis during pelvic surgery in a uterine transplantation model, Future Science OA, Vol: 4, Pages: FSO324-FSO324, ISSN: 2056-5623
Aim: Uterine transplantation (UTx) is proposed for treatment of uterine factor infertility. Our aim was to assess whether Endoscopic Laser Speckle Contrast Analysis (eLASCA) could evaluate pelvic blood flow at anastomotic sites required for sheep and rabbit UTx. Results/methodology: eLASCA detected blood flow in rabbit UTx #7 and #9. In sheep UTx #2, #3 and #5, the results allowed us to conclude that blood flow was present in the uterine graft following transplantation; and post-UTx, the animal had heart and respiratory rates, and oxygen saturation compatible with a normal hemodynamic status. Conclusion: These preliminary results establish the potential of Laser Speckle Contrast Analysis as noncontact and real-time tool for observation of spatially-resolved blood flow from which other parameters can be derived.
Deng L, Yan JD, Elson DS, et al., 2018, Characterization of an imaging multimode optical fiber using a digital micro-mirror device based single-beam system, Optics Express, Vol: 26, Pages: 18436-18447, ISSN: 1094-4087
This work demonstrates experimental approaches to characterize a single multimode fiber imaging system without a reference beam. Spatial light modulation is performed with a digital micro-mirror device that enables high-speed binary amplitude modulation. Intensity-only images are recorded by the camera and processed by a Bayesian inference based algorithm to retrieve the phase of the output optical field as well as the transmission matrix of the fiber. The calculated transmission matrix is validated by three standards: prediction accuracy, transmission imaging, and focus generation. Also, it is found that information on mode count and eigenchannels can be extracted from the transmission matrix by singular value decomposition. This paves the way for a more compact and cheaper single multimode fiber imaging system for many demanding imaging tasks.
Song L, Wang X, Zhang R, et al., 2018, Improving temporal resolution and speed sensitivity of laser speckle contrast analysis imaging based on noise reduction with an anisotropic diffusion filter, JOURNAL OF OPTICS, Vol: 20, ISSN: 2040-8978
The fluctuation of contrast caused by statistical noise degenerates the temporal/spatial resolution of laser speckle contrast imaging (LSCI) and limits the maximum speed when imaging. In this study, we investigated the application of the anisotropic diffusion filter (ADF) to temporal LSCI and found that the edge magnitude parameter of the ADF can be determined by the mean of the contrast image. Because the edge magnitude parameter is usually denoted as K, we term this the K-constant ADF (KC-ADF) and show that temporal sensitivity is improved when imaging because of the enhanced signal-to-noise ratio when using the KC-ADF in small-animal experiments. The cardiac cycle of a rat as high as 390 bpm can be imaged with an industrial camera.
Lin J, Clancy NT, Qi J, et al., 2018, Dual-modality endoscopic probe for tissue surface shape reconstruction and hyperspectral imaging enabled by deep neural networks., Medical Image Analysis, Vol: 48, Pages: 162-176, ISSN: 1361-8415
Surgical guidance and decision making could be improved with accurate and real-time measurement of intra-operative data including shape and spectral information of the tissue surface. In this work, a dual-modality endoscopic system has been proposed to enable tissue surface shape reconstruction and hyperspectral imaging (HSI). This system centers around a probe comprised of an incoherent fiber bundle, whose fiber arrangement is different at the two ends, and miniature imaging optics. For 3D reconstruction with structured light (SL), a light pattern formed of randomly distributed spots with different colors is projected onto the tissue surface, creating artificial texture. Pattern decoding with a Convolutional Neural Network (CNN) model and a customized feature descriptor enables real-time 3D surface reconstruction at approximately 12 frames per second (FPS). In HSI mode, spatially sparse hyperspectral signals from the tissue surface can be captured with a slit hyperspectral imager in a single snapshot. A CNN based super-resolution model, namely "super-spectral-resolution" network (SSRNet), has also been developed to estimate pixel-level dense hypercubes from the endoscope cameras standard RGB images and the sparse hyperspectral signals, at approximately 2 FPS. The probe, with a 2.1 mm diameter, enables the system to be used with endoscope working channels. Furthermore, since data acquisition in both modes can be accomplished in one snapshot, operation of this system in clinical applications is minimally affected by tissue surface movement and deformation. The whole apparatus has been validated on phantoms and tissue (ex vivo and in vivo), while initial measurements on patients during laryngeal surgery show its potential in real-world clinical applications.
Avila Rencoret FB, Mylonas G, Elson D, 2018, Robotic wide-field optical biopsy endoscopy, OSA Biophotonics Congress 2018, Publisher: OSA publishing
This paper describes a novel robotic framework for wide-field optical biopsy endoscopy, characterizes in vitro its spatial and spectral resolution, real time hyperspectral tissue classification, and demonstrates its feasibility on fresh porcine cadaveric colon.
Saso S, Clancy NT, Jones BP, et al., 2018, Use of biomedical photonics in gynecological surgery: a uterine transplantation model, Future Science OA, Vol: 4, Pages: FSO286-FSO286, ISSN: 2056-5623
Aim: Uterine transplantation (UTx) has been proposed as a treatment for permanent absolute uterine factor infertility. The study aims were to compare pulse oximetry and multispectral imaging (MSI), for intraoperative tracking of uterine oxygen saturation in animal UTx models (rabbit and sheep). Results/methodology: Imaging results confirmed the re-establishment of adequate perfusion in the transplanted organ after surgery. Comparison of oxygen saturation values between the pre-UTx donor and post-UTx recipient, and pre-UTx and post-UTx recipient reveals a statistically significant decrease in saturation levels post-UTx. Conclusion: The use of MSI is the first case in gynecology and has demonstrated promise of possible future human use. MSI technique has advantages over pulse oximetry - it provides spatial information in a real-time, noncontact manner.
Avila Rencoret FB, Mylonas GP, Elson D, Robotic Wide-Field Optical Biopsy Imaging For Flexible Endoscopy, 26th International Congress of the European Association for Endoscopic Surgery (EAES)
Elson D, Endoscopic technologies for surgical vision, IOP Optics in Clinical Practice IV
Elson D, Colour polarization-resolved imaging with clinical endoscopes (plenary), 3rd China Symposium on Polarimetry and Ellipsometry
Waldock W, Avila Rencoret F, Tincknell L, et al., Augmented intraoperative surgical vision for the assessment of gastrointestinal cancer resection margins, London Surgery Symposium
Bamber J, Shah A, Bush N, et al., Photoacoustic imaging and contrast agents in cancer research, Leeds Microbubble Symposium
Leiloglou M, Qi J, Rees Whippey D, et al., Guiding Fluorescence-Augmented Imaging System for Breast Cancer Surgery, EPSRC Image Guided Therapies Young Investigators
Li Q, Zhou X, Lin J, et al., Estimation of Tissue Oxygen Saturation from RGB Images based on Pixel-level Image Translation, Hamlyn Symposium on Medical Robotics
Zhao M, Oude Vrielink T, Elson D, et al., Endoscopic TORS-CYCLOPS: A Novel Cable-driven Parallel Robot for Transoral Laser Surgery, 26th Annual International EAES Congress
Elson D, Avila Rencoret F, Mylonas G, Robotic Wide-Field Optical Biopsy Imaging for Flexible Endoscopy (Gerhard Buess Technology Award), 26th Annual International EAES Congress
Leiloglou M, Qi J, Rees Whippey D, et al., Guiding Fluorescence-Augmented Imaging System for Breast Cancer Surgery, BMES Annual Meeting
Elson D, Polarization- and wavelength-resolved imaging with standard laparoscopes (invited), SPIE BiOS Molecular Guided Surgery
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