Imperial College London

Professor Dan Elson

Faculty of MedicineDepartment of Surgery & Cancer

Professor of Surgical Imaging
 
 
 
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Contact

 

+44 (0)20 7594 1700daniel.elson Website

 
 
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Location

 

415 Bessemer BuildingBessemer BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

395 results found

Huang B, Tsai Y-Y, Cartucho J, Vyas K, Tuch D, Giannarou S, Elson DSet al., 2020, Tracking and visualization of the sensing area for a tethered laparoscopic gamma probe, International Journal of Computer Assisted Radiology and Surgery, Vol: 15, Pages: 1389-1397, ISSN: 1861-6410

PurposeIn surgical oncology, complete cancer resection and lymph node identification are challenging due to the lack of reliable intraoperative visualization. Recently, endoscopic radio-guided cancer resection has been introduced where a novel tethered laparoscopic gamma detector can be used to determine the location of tracer activity, which can complement preoperative nuclear imaging data and endoscopic imaging. However, these probes do not clearly indicate where on the tissue surface the activity originates, making localization of pathological sites difficult and increasing the mental workload of the surgeons. Therefore, a robust real-time gamma probe tracking system integrated with augmented reality is proposed.MethodsA dual-pattern marker has been attached to the gamma probe, which combines chessboard vertices and circular dots for higher detection accuracy. Both patterns are detected simultaneously based on blob detection and the pixel intensity-based vertices detector and used to estimate the pose of the probe. Temporal information is incorporated into the framework to reduce tracking failure. Furthermore, we utilized the 3D point cloud generated from structure from motion to find the intersection between the probe axis and the tissue surface. When presented as an augmented image, this can provide visual feedback to the surgeons.ResultsThe method has been validated with ground truth probe pose data generated using the OptiTrack system. When detecting the orientation of the pose using circular dots and chessboard dots alone, the mean error obtained is 0.05∘and 0.06∘, respectively. As for the translation, the mean error for each pattern is 1.78 mm and 1.81 mm. The detection limits for pitch, roll and yaw are 360∘,360∘ and 8∘–82∘∪188∘–352∘.ConclusionThe performance evaluation results show that this dual-pattern marker can provide high detection rates, as well as more accurate pose estimation and a larger workspace than the previously proposed hyb

Journal article

Clancy NT, Jones G, Maier-Hein L, Elson DS, Stoyanov Det al., 2020, Surgical spectral imaging., Medical Image Analysis, Vol: 63, Pages: 1-18, ISSN: 1361-8415

Recent technological developments have resulted in the availability of miniaturised spectral imaging sensors capable of operating in the multi- (MSI) and hyperspectral imaging (HSI) regimes. Simultaneous advances in image-processing techniques and artificial intelligence (AI), especially in machine learning and deep learning, have made these data-rich modalities highly attractive as a means of extracting biological information non-destructively. Surgery in particular is poised to benefit from this, as spectrally-resolved tissue optical properties can offer enhanced contrast as well as diagnostic and guidance information during interventions. This is particularly relevant for procedures where inherent contrast is low under standard white light visualisation. This review summarises recent work in surgical spectral imaging (SSI) techniques, taken from Pubmed, Google Scholar and arXiv searches spanning the period 2013-2019. New hardware, optimised for use in both open and minimally-invasive surgery (MIS), is described, and recent commercial activity is summarised. Computational approaches to extract spectral information from conventional colour images are reviewed, as tip-mounted cameras become more commonplace in MIS. Model-based and machine learning methods of data analysis are discussed in addition to simulation, phantom and clinical validation experiments. A wide variety of surgical pilot studies are reported but it is apparent that further work is needed to quantify the clinical value of MSI/HSI. The current trend toward data-driven analysis emphasises the importance of widely-available, standardised spectral imaging datasets, which will aid understanding of variability across organs and patients, and drive clinical translation.

Journal article

Zhao M, Oude Vrielink TJC, Kogkas A, Runciman M, Elson D, Mylonas Get al., 2020, LaryngoTORS: a novel cable-driven parallel robotic system for transoral laser phonosurgery, IEEE Robotics and Automation Letters, Vol: 5, Pages: 1516-1523, ISSN: 2377-3766

Transoral laser phonosurgery is a commonly used surgical procedure in which a laser beam is used to perform incision, ablation or photocoagulation of laryngeal tissues. Two techniques are commonly practiced: free beam and fiber delivery. For free beam delivery, a laser scanner is integrated into a surgical microscope to provide an accurate laser scanning pattern. This approach can only be used under direct line of sight, which may cause increased postoperative pain to the patient and injury, is uncomfortable for the surgeon during prolonged operations, the manipulability is poor and extensive training is required. In contrast, in the fiber delivery technique, a flexible fiber is used to transmit the laser beam and therefore does not require direct line of sight. However, this can only achieve manual level accuracy, repeatability and velocity, and does not allow for pattern scanning. Robotic systems have been developed to overcome the limitations of both techniques. However, these systems offer limited workspace and degrees-of-freedom (DoF), limiting their clinical applicability. This work presents the LaryngoTORS, a robotic system that aims at overcoming the limitations of the two techniques, by using a cable-driven parallel mechanism (CDPM) attached at the end of a curved laryngeal blade for controlling the end tip of the laser fiber. The system allows autonomous generation of scanning patterns or user driven freepath scanning. Path scan validation demonstrated errors as low as 0.054±0.028 mm and high repeatability of 0.027±0.020 mm (6×2 mm arc line). Ex vivo tests on chicken tissue have been carried out. The results show the ability of the system to overcome limitations of current methods with high accuracy and repeatability using the superior fiber delivery approach.

Journal article

He C, Chang J, He H, Liu S, Elson DS, Ma H, Booth MJet al., 2020, GRIN lens based polarization endoscope – from conception to application, Label-free Biomedical Imaging and Sensing (LBIS) 2020, Publisher: SPIE

Graded index (GRIN) lenses focus light through a radially symmetric refractive index profile. It is not widely appreciated that the ion-exchange process that creates the index profile also causes a radially symmetric birefringence variation. This property is usually considered a nuisance, such that manufacturing processes are optimized to keep it to a minimum. Here, a new Mueller matrix (MM) polarimeter based on a spatially engineered polarization state generating array and GRIN lens cascade for measuring the MM of a region of a sample in a single-shot is presented. We explore using the GRIN lens cascade for a functional analyzer to calculate multiple Stokes vectors and the MM of the target in a snapshot. A designed validation sample is used to test the reliability of this polarimeter. To understand more potential biomedical applications, human breast ductal carcinoma slides at two pathological progression stages are detected by this polarimeter. The MM polar decomposition parameters then can be calculated from the measured MMs, and quantitatively compared with the equivalent data sampled by a MM microscope. The results indicate that the polarimeter and the measured polarization parameters are capable of differentiating the healthy and carcinoma status of human breast tissue efficiently. It has potential to act as a polarization detected fiber-based probe to assist further minimally invasive clinical diagnosis.

Conference paper

He C, Chang J, Hu Q, Wang J, Antonello J, He H, Liu S, Lin J, Dai B, Elson DS, Xi P, Ma H, Booth MJet 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.

Journal article

Chabloz N, Wenzel M, Perry H, Yoon I, Molisso S, Stasiuk G, Elson D, Cass A, Wilton-Ely Jet al., 2019, Polyfunctionalised nanoparticles bearing robust gadolinium surface units for high relaxivity performance in MRI, Chemistry - A European Journal, Vol: 25, Pages: 10895-10906, 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.

Journal article

Li Q, Lin J, Clancy NT, Elson DSet 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, Vol: 14, Pages: 987-995, 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.

Journal article

Brunckhorst O, Ong QJ, Elson D, Mayer Eet 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

Journal article

Adshead J, Oldfield F, Hadaschik B, Everaerts W, Mestre-Fusco A, Newbery M, Elson D, Grootendorst M, Vyas K, Fumado L, Harke Net 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

Conference paper

Qi J, Elson D, Stoyanov D, 2019, An eigen value calibration method and optimization for 3×3 Mueller polarimeters, Optics Letters, Vol: 44, Pages: 2362-2365, ISSN: 0146-9592

3×3 Mueller polarimetry has shown potential for tissue characterization applications, however, calibration has not been fully addressed. We demonstrate a 3×3 Mueller polarimeter eigenvalue calibration method, inspired by those for full Mueller polarimeters. We also investigate the optimal combination of calibration measurements. Our method does not rely on modeling the polarization state generator, polarization state analyzer, or precise knowledge of calibration sample properties or orientations. It is therefore easy to implement, and the experimental results of a linear polarizer test sample, as well as a biological specimen, are presented.

Journal article

Lin J, Walsted ES, Backer V, Hull JH, Elson Det 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.

Journal article

Sheng W, Li W, Qi J, Liu T, He H, Dong Y, Liu S, Wu J, Elson DS, Ma Het 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.

Journal article

Singh M, Nabavi E, Zhou Y, Gallina ME, Zhao H, Ruenraroengsak P, Porter AE, Ma D, Cass AEG, Hanna GB, Elson DSet 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.

Journal article

Adshead J, Oldfield F, Hadaschik B, Everaerts W, Mestre-Fusco A, Newbery M, Elson D, Grootendorst M, Vyas K, Fumado L, Harke Net al., 2019, Usability and technical feasibility evaluation of a tethered laparoscopic gamma probe for radioguided surgery in prostate cancer: a pelvic phantom and porcine model study (19-1271), Annual Meeting of the American Urological Association Education and Research Inc.

Conference paper

Elson D, Adshead J, Oldfield F, Hadaschik B, Everaerts W, Mestre A, Newbery M, Grootendorst M, Vyas K, Fumado L, Harke Net al., 2019, A tethered laparoscopic gamma probe for radioguided surgery in prostate cancer – usability and technical feasibility evaluation in a pelvic phantom and porcine model (best poster - New Technologies), 34th Annual European Association of Urology Congress

Conference paper

Brunckhorst O, Ong, Qi Jia, Elson D, Mayer Eet al., 2019, Novel Modalities for Real-Time Optical Imaging in Urological Neoplasms: A Systematic Review, 34th Annual European Association of Urology Congress

Conference paper

Elson D, 2019, Optical theranostics: image-guided cancer thermal therapy using light (invited), Computer Assisted Radiology and Surgery (Europe's Got Talent)

Conference paper

Elson D, 2019, Multispectral and polarization-resolved endoscopic surgical imaging (invited), Aslla Symposium: Molecular-Guided Optical Theranostics 2030

Conference paper

Elson D, 2019, Multimodality Optical Endoscopy for Surgical Imaging (invited), Society of Academic and Research Surgery Annual Meeting

Conference paper

Kedrzycki M, Leiloglou M, Chalau V, Leff D, Elson Det al., 2019, Highlighting Breast Cancer: First-in-Human Testing of the Imperial Camera System for Fluorescence Guided Breast Cancer Surgery, London Surgery Symposium

Conference paper

Leiloglou M, Chalau V, Kedrzycki M, Avila-Rencoret F, Li Q, Lin J, Hanna G, Darzi A, Leff D, Elson Det al., 2019, Snapshot Fluorescence Hyperspectral System for Breast Cancer Surgery Guidance, Hamlyn Symposium Advanced Biophotonics Workshop

Conference paper

Leiloglou M, Chalau V, Kedrzycki M, Qi J, Martin-Gonzalez P, Hanna G, Darzi A, Leff D, Elson Det al., 2019, Fluorescence Intensity Image Guided Breast Conserving Surgery (BCS)., European Molecular Imaging Meeting

Conference paper

Elson DS, 2019, Interventional imaging: Biophotonics, Handbook of Medical Image Computing and Computer Assisted Intervention, Pages: 747-775, ISBN: 9780128161760

© 2020 Elsevier Inc. All rights reserved. Since the beginning of medicine, optical imaging has formed a central pillar for the diagnosis and treatment of disease. The 20th century saw the development of many other diagnostic imaging methods - CT, MRI, nuclear methods, etc. - but optical imaging remains of paramount importance. The minimally invasive surgery revolution has been enabled by the detection of the surgical field with a color camera system that is either mounted on the proximal end of an endoscope or in more recent times miniaturized and placed at the tip. The color responses of the red-green-blue image data are well matched to the human eye and can be presented on a color display to the surgeon in the operating theater for direct visual guidance of the intervention. However, while this provides a visually recognizable picture of the tissue to the surgeon, it misses the potential of light to reveal otherwise invisible tissue information. Within the last few decades alternative optical imaging methods have started to become more widely used and it is the potential of biophotonics techniques to guide interventions that will be explored in this chapter. Descriptions will be provided to explain how these additional signals may be collected, understood, and applied to different diseases.

Book chapter

Zhao M, Oude Vrielink J, Kogkas A, Mylonas G, Elson Det al., 2019, Prototype Designs of a Cable-driven Parallel Robot for Transoral Laser Surgery, Hamlyn Symposium on Medical Robotics

Conference paper

Li Q, Lin J, Clancy N, Elson Det al., 2019, Estimation of Tissue Oxygen Saturation from RGB images and Sparse Hyperspectral Signals based on Conditional Generative Adversarial Network, Information Processing in Computer Aided Intervention

Conference paper

Waldock WJ, Avila-Rencoret FB, Tincknell LG, Murphy J, Elson DS, Peters CJet 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

Conference paper

Elson DS, Cleary K, Dupont P, Merrifield R, Riviere Cet al., 2018, Medical robotics, Annals of Biomedical Engineering, Vol: 46, Pages: 1433-1436, ISSN: 0090-6964

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.

Journal article

Walsted ES, Lin J, Elson DS, Hull JHet 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

Conference paper

Zhao T, Deng L, Wang W, Elson DS, Su Let 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.

Journal article

Saso S, Tziraki M, Clancy NT, Song L, Bracewell-Milnes T, Jones BP, Al-Memar M, Yazbek J, Thum M-Y, Sayasneh A, Bourne T, Smith JR, Elson DS, Ghaem-Maghami Set 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.

Journal article

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