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Gordon GSD, Warburton S, Parkes S, Kerridge A, Parra-Blanco A, Ortiz-Fernandez-Sordo J, Fitzgerald RC. Cytosponge procedures produce fewer respiratory aerosols and droplets than esophagogastroduodenoscopies. Dis Esophagus 2024; 37:doad061. [PMID: 37899140 PMCID: PMC10906705 DOI: 10.1093/dote/doad061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/28/2023] [Accepted: 10/14/2023] [Indexed: 10/31/2023]
Abstract
Esophagogastroduodenoscopies (EGD) are aerosol-generating procedures that may spread respiratory pathogens. We aim to investigate the production of airborne aerosols and droplets during Cytosponge procedures, which are being evaluated in large-scale research studies and National Health Service (NHS)implementation pilots to reduce endoscopy backlogs. We measured 18 Cytosponge and 37 EGD procedures using a particle counter (diameters = 0.3-25 μm), taking measurements 10 cm from the mouth. Two particle count analyses were performed: whole procedure and event-based. Direct comparison with duration-standardized EGD procedures shows that Cytosponge procedures produce 2.16× reduction (P < 0.001) for aerosols and no significant change for droplets (P = 0.332). Event-based analysis shows that particle production is driven by throat spray (aerosols: 138.1× reference, droplets: 16.2×), which is optional, and removal of Cytosponge (aerosols: 14.6×, droplets: 62.6×). Cytosponge burping produces less aerosols than EGD (2.82×, P < 0.05). Cytosponge procedures produce significantly less aerosols and droplets than EGD procedures and thus reduce two potential transmission routes for respiratory viruses.
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Affiliation(s)
- George S D Gordon
- Department of Electrical and Electronic Engineering, University of Nottingham, Nottingham, UK
| | - Samantha Warburton
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and the University of Nottingham, Queens Medical Centre, Derby Road, Nottingham NG7 2UH, UK
| | - Sian Parkes
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and the University of Nottingham, Queens Medical Centre, Derby Road, Nottingham NG7 2UH, UK
| | - Abigail Kerridge
- Early Cancer Institute, Department of Oncology, University of Cambridge, Adrian Way, Cambridge CB2 0XZ, UK
| | - Adolfo Parra-Blanco
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and the University of Nottingham, Queens Medical Centre, Derby Road, Nottingham NG7 2UH, UK
| | - Jacobo Ortiz-Fernandez-Sordo
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and the University of Nottingham, Queens Medical Centre, Derby Road, Nottingham NG7 2UH, UK
| | - Rebecca C Fitzgerald
- Early Cancer Institute, Department of Oncology, University of Cambridge, Adrian Way, Cambridge CB2 0XZ, UK
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Crowley J, Gordon GSD. Ultra-miniature dual-wavelength spatial frequency domain imaging for micro-endoscopy. J Biomed Opt 2024; 29:026002. [PMID: 38312854 PMCID: PMC10832795 DOI: 10.1117/1.jbo.29.2.026002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 11/08/2023] [Accepted: 11/14/2023] [Indexed: 02/06/2024]
Abstract
Significance There is a need for a cost-effective, quantitative imaging tool that can be deployed endoscopically to better detect early stage gastrointestinal cancers. Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that produces near-real time, quantitative maps of absorption and reduced scattering coefficients, but most implementations are bulky and suitable only for use outside the body. Aim We aim to develop an ultra-miniature SFDI system comprising an optical fiber array (diameter 0.125 mm) and a micro camera (1 × 1 mm package) to displace conventionally bulky components, in particular, the projector. Approach First, we fabricated a prototype with an outer diameter of 3 mm, although the individual component dimensions could permit future packaging to a < 1.5 mm diameter. We developed a phase-tracking algorithm to rapidly extract images with fringe projections at three equispaced phase shifts to perform SFDI demodulation. Results To validate the performance, we first demonstrate comparable recovery of quantitative optical properties between our ultra-miniature system and a conventional bench-top SFDI system with an agreement of 15% and 6% for absorption and reduced scattering, respectively. Next, we demonstrate imaging of absorption and reduced scattering of tissue-mimicking phantoms providing enhanced contrast between simulated tissue types (healthy and tumour), done simultaneously at wavelengths of 515 and 660 nm. Using a support vector machine classifier, we estimate that sensitivity and specificity values of > 90 % are feasible for detecting simulated squamous cell carcinoma. Conclusions This device shows promise as a cost-effective, quantitative imaging tool to detect variations in optical absorption and scattering as indicators of cancer.
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Affiliation(s)
- Jane Crowley
- University of Nottingham, Department of Electrical and Electronic Engineering, Optics and Photonics Group, Nottingham, United Kingdom
| | - George S. D. Gordon
- University of Nottingham, Department of Electrical and Electronic Engineering, Optics and Photonics Group, Nottingham, United Kingdom
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Phillips F, Crowley J, Warburton S, Parra-Blanco A, Gordon GSD. Bronchoscopy masks mitigate aerosols during upper gastrointestinal endoscopies. Endosc Int Open 2023; 11:E1001-E1004. [PMID: 37941538 PMCID: PMC10629208 DOI: 10.1055/a-2173-1711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 08/17/2023] [Indexed: 11/10/2023] Open
Abstract
Background and study aims Upper gastrointestinal endoscopies are considered aerosol-generating procedures (AGP) that risk spread of airborne diseases such as SARS-CoV-2. We aimed to investigate where clinically approved bronchoscopy masks applied to patients during esophagogastroduodenoscopies can mitigate spread of aerosols and droplets. Patients and methods This study included patients undergoing routine upper gastrointestinal endoscopy in a standard endoscopy room and used a particle counter to measure size and number of particles 10 cm from the mouths of 49 patients undergoing upper gastrointestinal endoscopies, of whom 12 wore bronchoscopy masks and 37 did not (controls). Particle counts in the aerosol (≤ 5 µm diameter) and droplet (> 5 µm-diameter) size ranges were measured and averaged over the duration of procedures. Results The use of bronchoscopy masks offers a 47% reduction ( P = 0.01) in particle count for particles < 5 μm in diameter over the procedure duration (aerosols). Conclusions Bronchoscopy masks or similar are a simple, low-cost mitigation technique that can be used during outbreaks of respiratory diseases such as COVID-19 to improve safety and reduce fallow times.
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Affiliation(s)
- Frank Phillips
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and University of Nottingham, Nottingham, United Kingdom
| | - Jane Crowley
- Department of Electrical and Electronic Engineering, University of Nottingham, Nottingham, United Kingdom of Great Britain and Northern Ireland
| | - Samantha Warburton
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and University of Nottingham, Nottingham, United Kingdom
| | - Adolfo Parra-Blanco
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and University of Nottingham, Nottingham, United Kingdom
| | - George S. D. Gordon
- Department of Electrical and Electronic Engineering, University of Nottingham, Nottingham, United Kingdom of Great Britain and Northern Ireland
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Crowley J, Gordon GSD. Designing and simulating realistic spatial frequency domain imaging systems using open-source 3D rendering software. Biomed Opt Express 2023; 14:2523-2538. [PMID: 37342713 PMCID: PMC10278632 DOI: 10.1364/boe.484286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 04/24/2023] [Accepted: 04/25/2023] [Indexed: 06/23/2023]
Abstract
Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that maps absorption and reduced scattering coefficients, offering improved contrast for important tissue structures such as tumours. Practical SFDI systems must cope with various imaging geometries including imaging planar samples ex vivo, imaging inside tubular lumen in vivo e.g. for endoscopy, and measuring tumours or polyps of varying morphology. There is a need for a design and simulation tool to accelerate design of new SFDI systems and simulate realistic performance under these scenarios. We present such a system implemented using open-source 3D design and ray-tracing software Blender that simulates media with realistic absorption and scattering in a wide range of geometries. By using Blender's Cycles ray-tracing engine, our system simulates effects such as varying lighting, refractive index changes, non-normal incidence, specular reflections and shadows, enabling realistic evaluation of new designs. We first demonstrate quantitative agreement between Monte-Carlo simulated absorption and reduced scattering coefficients with those simulated from our Blender system, achieving 16 % discrepancy in absorption coefficient and 18 % in reduced scattering coefficient. However, we then show that using an empirically derived look-up table the errors reduce to 1 % and 0.7 % respectively. Next, we simulate SFDI mapping of absorption, scattering and shape for simulated tumour spheroids, demonstrating enhanced contrast. Finally we demonstrate SFDI mapping inside a tubular lumen, which highlighted a important design insight: custom look-up tables must be generated for different longitudinal sections of the lumen. With this approach we achieved 2 % absorption error and 2 % scattering error. We anticipate our simulation system will aid in the design of novel SFDI systems for key biomedical applications.
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Affiliation(s)
- Jane Crowley
- Optics & Photonics Group, Department of Electrical and
Electronic Engineering, University of Nottingham, Nottingham, United
Kingdom
| | - George S. D. Gordon
- Optics & Photonics Group, Department of Electrical and
Electronic Engineering, University of Nottingham, Nottingham, United
Kingdom
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Mouthaan R, Christopher PJ, Kadis A, Gordon GSD, Wilkinson TD, Euser TG. Effects of measurement noise on the construction of a transmission matrix. J Opt Soc Am A Opt Image Sci Vis 2022; 39:2026-2034. [PMID: 36520699 DOI: 10.1364/josaa.464916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 09/28/2022] [Indexed: 06/17/2023]
Abstract
The effects of time-varying measurement noise on transmission matrix acquisition processes are considered for the first time, to our knowledge. Dominant noise sources are discussed, and the noise properties of a typical interferometer system used for characterizing a multimode fiber transmission matrix are quantified. It is demonstrated that an appropriate choice of measurement basis allows a more accurate transmission matrix to be more quickly obtained in the presence of measurement noise. Finally, it is shown that characterizing the noise figure of the experimental system allows the inverse transmission matrix to be constructed with an ideal amount of regularization, which can in turn be used for optimal image acquisition.
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Phillips F, Crowley J, Warburton S, Gordon GSD, Parra-Blanco A. Aerosol and droplet generation in upper and lower GI endoscopy: whole procedure and event-based analysis. Gastrointest Endosc 2022; 96:603-611.e0. [PMID: 35659608 PMCID: PMC9386278 DOI: 10.1016/j.gie.2022.05.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 04/18/2022] [Accepted: 05/24/2022] [Indexed: 12/11/2022]
Abstract
BACKGROUND AND AIMS Aerosol-generating procedures have become an important healthcare issue during the coronavirus disease 2019 (COVID-19) pandemic because the severe acute respiratory syndrome coronavirus 2 virus can be transmitted through aerosols. We aimed to characterize aerosol and droplet generation in GI endoscopy, where there is little evidence. METHODS This prospective observational study included 36 patients undergoing routine peroral gastroscopy (POG), 11 undergoing transnasal endoscopy (TNE), and 48 undergoing lower GI (LGI) endoscopy. Particle counters took measurements near the appropriate orifice (2 models were used with diameter ranges of .3-25 μm and 20-3000 μm). Quantitative analysis was performed by recording specific events and subtracting background particles. RESULTS POG produced 1.96 times the level of background particles (P < .001) and TNE produced 2.00 times (P < .001), but a direct comparison showed POG produced 2.00 times more particles than TNE. LGI procedures produced significant particle counts (P < .001) with 2.4 times greater production per procedure than POG but only .63 times production per minute. Events that were significant relative to the room background particle count were POG, with throat spray (150.0 times, P < .001), esophageal extubation (37.5 times, P < .001), and coughing or gagging (25.8 times, P < .01); TNE, with nasal spray (40.1 times, P < .001), nasal extubation (32.0 times, P < .01), and coughing or gagging (20.0, P < .01); and LGI procedures, with rectal intubation (9.9 times, P < .05), rectal extubation (27.2 times, P < .01), application of abdominal pressure (9.6 times, P < .05), and rectal insufflation or retroflexion (7.7 times, P < .01). These all produced particle counts larger than or comparable with volitional cough. CONCLUSIONS GI endoscopy performed through the mouth, nose, or rectum generates significant quantities of aerosols and droplets. Because the infectivity of procedures is not established, we therefore suggest adequate personal protective equipment is used for all GI endoscopy where there is a high population prevalence of COVID-19. Avoiding throat and nasal spray would significantly reduce particles generated from upper GI procedures.
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Affiliation(s)
- Frank Phillips
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, Nottingham, UK
| | | | - Samantha Warburton
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, Nottingham, UK; Faculty of Engineering, Nottingham, UK
| | | | - Adolfo Parra-Blanco
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust, Nottingham, UK
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Osman A, Crowley J, Gordon GSD. Training generative adversarial networks for optical property mapping using synthetic image data. Biomed Opt Express 2022; 13:5171-5186. [PMID: 36425623 PMCID: PMC9664886 DOI: 10.1364/boe.458554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 06/13/2022] [Accepted: 06/13/2022] [Indexed: 06/16/2023]
Abstract
We demonstrate the training of a generative adversarial network (GAN) for the prediction of optical property maps (scattering and absorption) using spatial frequency domain imaging (SFDI) image data sets that are generated synthetically with a free open-source 3D modelling and rendering software, Blender. The flexibility of Blender is exploited to simulate 5 models with real-life relevance to clinical SFDI of diseased tissue: flat samples containing a single material, flat samples containing 2 materials, flat samples containing 3 materials, flat samples with spheroidal tumours and cylindrical samples with spheroidal tumours. The last case is particularly relevant as it represents wide-field imaging inside a tubular organ e.g. the gastro-intestinal tract. In all 5 scenarios we show the GAN provides an accurate reconstruction of the optical properties from single SFDI images with a mean normalised error ranging from 1.0-1.2% for absorption and 1.1%-1.2% for scattering, resulting in visually improved contrast for tumour spheroid structures. This compares favourably with the ∼10% absorption error and ∼10% scattering error achieved using GANs on experimental SFDI data. Next, we perform a bi-directional cross-validation of our synthetically-trained GAN, retrained with 90% synthetic and 10% experimental data to encourage domain transfer, with a GAN trained fully on experimental data and observe visually accurate results with an error of 6.3%-10.3% for absorption and 6.6%-11.9% for scattering. Our synthetically trained GAN is therefore highly relevant to real experimental samples but provides the significant added benefits of large training datasets, perfect ground-truths and the ability to test realistic imaging geometries, e.g. inside cylinders, for which no conventional single-shot demodulation algorithms exist. In the future, we expect that the application of techniques such as domain adaptation or training on hybrid real-synthetic datasets will create a powerful tool for fast, accurate production of optical property maps for real clinical imaging systems.
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Affiliation(s)
- A Osman
- Optics and Photonics Group, Faculty of Engineering, The University of Nottingham, Nottingham, United Kingdom
| | - J Crowley
- Optics and Photonics Group, Faculty of Engineering, The University of Nottingham, Nottingham, United Kingdom
| | - G S D Gordon
- Optics and Photonics Group, Faculty of Engineering, The University of Nottingham, Nottingham, United Kingdom
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Mouthaan R, Christopher PJ, Gordon GSD, Wilkinson TD, Euser TG. Robust correction of interferometer phase drift in transmission matrix measurements. Appl Opt 2022; 61:4315-4321. [PMID: 36256291 DOI: 10.1364/ao.454679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 04/22/2022] [Indexed: 06/16/2023]
Abstract
A complex-valued transmission matrix describing a scattering medium can be constructed from a sequence of many interferometric measurements. A major challenge in such experiments is to correct for rapid phase drift of the optical system during the data acquisition process, especially when the phase drifts significantly between consecutive measurements. Therefore, a new method is presented where the exact phase drift between two measurements is characterized and corrected using a single additional measurement. This approach removes the need to continuously track the phase and significantly relaxes the phase stability requirements of the interferometer, allowing transmission matrices to be constructed in the presence of fast and erratic phase drift.
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9
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Fitzpatrick CRM, Wilson A, Sawyer TW, Christopher PJ, Wilkinson TD, Bohndiek SE, Gordon GSD. Robustness to misalignment of low-cost, compact quantitative phase imaging architectures. OSA Contin 2020; 3:2660-2679. [PMID: 34222834 PMCID: PMC8219376 DOI: 10.1364/osac.395498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 05/30/2023]
Abstract
Non-interferometric approaches to quantitative phase imaging could enable its application in low-cost, miniaturised settings such as capsule endoscopy. We present two possible architectures and both analyse and mitigate the effect of sensor misalignment on phase imaging performance. This is a crucial step towards determining the feasibility of implementing phase imaging in a capsule device. First, we investigate a design based on a folded 4f correlator, both in simulation and experimentally. We demonstrate a novel technique for identifying and compensating for axial misalignment and explore the limits of the approach. Next, we explore the implications of axial and transverse misalignment, and of manufacturing variations on the performance of a phase plate-based architecture, identifying a clear trade-off between phase plate resolution and algorithm convergence time. We conclude that while the phase plate architecture is more robust to misalignment, both architectures merit further development with the goal of realising a low-cost, compact system for applying phase imaging in capsule endoscopy.
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Affiliation(s)
| | - Abby Wilson
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Travis W. Sawyer
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Peter J. Christopher
- Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Timothy D. Wilkinson
- Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Sarah E. Bohndiek
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - George S. D. Gordon
- Department of Electrical and Electronic Engineering, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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Williams C, Gordon GSD, Wilkinson TD, Bohndiek SE. Grayscale-to-Color: Scalable Fabrication of Custom Multispectral Filter Arrays. ACS Photonics 2019; 6:3132-3141. [PMID: 31921939 PMCID: PMC6943817 DOI: 10.1021/acsphotonics.9b01196] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Indexed: 05/21/2023]
Abstract
Snapshot multispectral image (MSI) sensors have been proposed as a key enabler for a plethora of multispectral imaging applications, from diagnostic medical imaging to remote sensing. With each application requiring a different set, and number, of spectral bands, the absence of a scalable, cost-effective manufacturing solution for custom multispectral filter arrays (MSFAs) has prevented widespread MSI adoption. Despite recent nanophotonic-based efforts, such as plasmonic or high-index metasurface arrays, large-area MSFA manufacturing still consists of many-layer dielectric (Fabry-Perot) stacks, requiring separate complex lithography steps for each spectral band and multiple material compositions for each. It is an expensive, cumbersome, and inflexible undertaking, but yields optimal optical performance. Here, we demonstrate a manufacturing process that enables cost-effective wafer-level fabrication of custom MSFAs in a single lithographic step, maintaining high efficiencies (∼75%) and narrow line widths (∼25 nm) across the visible to near-infrared. By merging grayscale (analog) lithography with metal-insulator-metal (MIM) Fabry-Perot cavities, whereby exposure dose controls cavity thickness, we demonstrate simplified fabrication of MSFAs up to N-wavelength bands. The concept is first proven using low-volume electron beam lithography, followed by the demonstration of large-volume UV mask-based photolithography with MSFAs produced at the wafer level. Our framework provides an attractive alternative to conventional MSFA manufacture and metasurface-based spectral filters by reducing both fabrication complexity and cost of these intricate optical devices, while increasing customizability.
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Affiliation(s)
- Calum Williams
- Electrical
Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, U.K.
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, U.K.
| | - George S. D. Gordon
- Electrical
Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, U.K.
| | - Timothy D. Wilkinson
- Electrical
Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, U.K.
| | - Sarah E. Bohndiek
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, U.K.
- Cancer
Research UK Cambridge Institute, University
of Cambridge, Robinson Way, Cambridge, CB2 0RE, U.K.
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Gordon GSD, Joseph J, Alcolea MP, Sawyer T, Williams C, Fitzpatrick CRM, Jones PH, di Pietro M, Fitzgerald RC, Wilkinson TD, Bohndiek SE. Quantitative phase and polarization imaging through an optical fiber applied to detection of early esophageal tumorigenesis. J Biomed Opt 2019; 24:1-13. [PMID: 31840442 PMCID: PMC7006047 DOI: 10.1117/1.jbo.24.12.126004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 11/18/2019] [Indexed: 05/30/2023]
Abstract
Phase and polarization of coherent light are highly perturbed by interaction with microstructural changes in premalignant tissue, holding promise for label-free detection of early tumors in endoscopically accessible tissues such as the gastrointestinal tract. Flexible optical multicore fiber (MCF) bundles used in conventional diagnostic endoscopy and endomicroscopy scramble phase and polarization, restricting clinicians instead to low-contrast amplitude-only imaging. We apply a transmission matrix characterization approach to produce full-field en-face images of amplitude, quantitative phase, and resolved polarimetric properties through an MCF. We first demonstrate imaging and quantification of biologically relevant amounts of optical scattering and birefringence in tissue-mimicking phantoms. We present an entropy metric that enables imaging of phase heterogeneity, indicative of disordered tissue microstructure associated with early tumors. Finally, we demonstrate that the spatial distribution of phase and polarization information enables label-free visualization of early tumors in esophageal mouse tissues, which are not identifiable using conventional amplitude-only information.
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Affiliation(s)
- George S. D. Gordon
- University of Cambridge, Department of Engineering, Cambridge, United Kingdom
| | - James Joseph
- University of Cambridge, Department of Physics, Cavendish Laboratory, Cambridge, United Kingdom
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Cambridge, United Kingdom
| | - Maria P. Alcolea
- University of Cambridge, Wellcome Trust MRC Stem Cell Institute, Cambridge, United Kingdom
| | - Travis Sawyer
- University of Cambridge, Department of Physics, Cavendish Laboratory, Cambridge, United Kingdom
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Cambridge, United Kingdom
| | - Calum Williams
- University of Cambridge, Department of Engineering, Cambridge, United Kingdom
- University of Cambridge, Department of Physics, Cavendish Laboratory, Cambridge, United Kingdom
| | | | - Philip H. Jones
- University of Cambridge, MRC Cancer Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Massimiliano di Pietro
- University of Cambridge, MRC Cancer Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Rebecca C. Fitzgerald
- University of Cambridge, MRC Cancer Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | | | - Sarah E. Bohndiek
- University of Cambridge, Department of Physics, Cavendish Laboratory, Cambridge, United Kingdom
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Cambridge, United Kingdom
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Gordon GSD, Joseph J, Sawyer T, Macfaden AJ, Williams C, Wilkinson TD, Bohndiek SE. Full-field quantitative phase and polarisation-resolved imaging through an optical fibre bundle. Opt Express 2019; 27:23929-23947. [PMID: 31510290 PMCID: PMC6825613 DOI: 10.1364/oe.27.023929] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/11/2019] [Accepted: 07/11/2019] [Indexed: 05/06/2023]
Abstract
Flexible optical fibres, used in conventional medical endoscopy and industrial inspection, scramble phase and polarisation information, restricting users to amplitude-only imaging. Here, we exploit the near-diagonality of the multi-core fibre (MCF) transmission matrix in a parallelised fibre characterisation architecture, enabling accurate imaging of quantitative phase (error <0.3 rad) and polarisation-resolved (errors <10%) properties. We first demonstrate accurate recovery of optical amplitude and phase in two polarisations through the MCF by measuring and inverting the transmission matrix, and then present a robust Bayesian inference approach to resolving 5 polarimetric properties of samples. Our method produces high-resolution (9.0±2.6μm amplitude, phase; 36.0±10.4μm polarimetric) full-field images at working distances up to 1mm over a field-of-view up to 750×750μm 2 using an MCF with potential for flexible operation. We demonstrate the potential of using quantitative phase for computational image focusing and polarisation-resolved properties in imaging birefringence.
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Affiliation(s)
- George S. D. Gordon
- Now at: Department of Electrical and Electronic Engineering, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
- Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
| | - James Joseph
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Travis Sawyer
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Alexander J. Macfaden
- Now at: Department of Electrical and Electronic Engineering, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Calum Williams
- Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Timothy D. Wilkinson
- Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Sarah E. Bohndiek
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
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Yoon J, Joseph J, Waterhouse DJ, Luthman AS, Gordon GSD, di Pietro M, Januszewicz W, Fitzgerald RC, Bohndiek SE. A clinically translatable hyperspectral endoscopy (HySE) system for imaging the gastrointestinal tract. Nat Commun 2019; 10:1902. [PMID: 31015458 PMCID: PMC6478902 DOI: 10.1038/s41467-019-09484-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/12/2019] [Indexed: 02/06/2023] Open
Abstract
Hyperspectral imaging (HSI) enables visualisation of morphological and biochemical information, which could improve disease diagnostic accuracy. Unfortunately, the wide range of image distortions that arise during flexible endoscopy in the clinic have made integration of HSI challenging. To address this challenge, we demonstrate a hyperspectral endoscope (HySE) that simultaneously records intrinsically co-registered hyperspectral and standard-of-care white light images, which allows image distortions to be compensated computationally and an accurate hyperspectral data cube to be reconstructed as the endoscope moves in the lumen. Evaluation of HySE performance shows excellent spatial, spectral and temporal resolution and high colour fidelity. Application of HySE enables: quantification of blood oxygenation levels in tissue mimicking phantoms; differentiation of spectral profiles from normal and pathological ex vivo human tissues; and recording of hyperspectral data under freehand motion within an intact ex vivo pig oesophagus model. HySE therefore shows potential for enabling HSI in clinical endoscopy.
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Affiliation(s)
- Jonghee Yoon
- Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - James Joseph
- Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Dale J Waterhouse
- Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - A Siri Luthman
- Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - George S D Gordon
- Department of Engineering, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Massimiliano di Pietro
- MRC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, CB2 0XZ, UK
| | - Wladyslaw Januszewicz
- MRC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, CB2 0XZ, UK
| | - Rebecca C Fitzgerald
- MRC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, CB2 0XZ, UK
| | - Sarah E Bohndiek
- Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK.
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK.
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Gataric M, Gordon GSD, Renna F, Ramos AGCP, Alcolea MP, Bohndiek SE. Reconstruction of Optical Vector-Fields With Applications in Endoscopic Imaging. IEEE Trans Med Imaging 2019; 38:955-967. [PMID: 30334753 PMCID: PMC6456146 DOI: 10.1109/tmi.2018.2875875] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 10/09/2018] [Indexed: 05/03/2023]
Abstract
We introduce a framework for the reconstruction of the amplitude, phase, and polarization of an optical vector-field using measurements acquired by an imaging device characterized by an integral transform with an unknown spatially variant kernel. By incorporating effective regularization terms, this new approach is able to recover an optical vector-field with respect to an arbitrary representation system, which may be different from the one used for device calibration. In particular, it enables the recovery of an optical vector-field with respect to a Fourier basis, which is shown to yield indicative features of increased scattering associated with tissue abnormalities. We demonstrate the effectiveness of our approach using synthetic holographic images and biological tissue samples in an experimental setting, where the measurements of an optical vector-field are acquired by a multicore fiber endoscope, and observe that indeed the recovered Fourier coefficients are useful in distinguishing healthy tissues from tumors in early stages of oesophageal cancer.
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Waterhouse DJ, Luthman AS, Yoon J, Gordon GSD, Bohndiek SE. Quantitative evaluation of comb-structure correction methods for multispectral fibrescopic imaging. Sci Rep 2018; 8:17801. [PMID: 30542081 PMCID: PMC6290790 DOI: 10.1038/s41598-018-36088-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 11/13/2018] [Indexed: 02/07/2023] Open
Abstract
Removing the comb artifact introduced by imaging fibre bundles, or 'fibrescopes', for example in medical endoscopy, is essential to provide high quality images to the observer. Multispectral imaging (MSI) is an emerging method that combines morphological (spatial) and chemical (spectral) information in a single data 'cube'. When a fibrescope is coupled to a spectrally resolved detector array (SRDA) to perform MSI, comb removal is complicated by the demosaicking step required to reconstruct the multispectral data cube. To understand the potential for using SRDAs as multispectral imaging sensors in medical endoscopy, we assessed five comb correction methods with respect to five performance metrics relevant to biomedical imaging applications: processing time, resolution, smoothness, signal and the accuracy of spectral reconstruction. By assigning weights to each metric, which are determined by the particular imaging application, our results can be used to select the correction method to achieve best overall performance. In most cases, interpolation gave the best compromise between the different performance metrics when imaging using an SRDA.
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Affiliation(s)
- Dale J Waterhouse
- Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, CB2 0RE, UK
| | - A Siri Luthman
- Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, CB2 0RE, UK
| | - Jonghee Yoon
- Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, CB2 0RE, UK
| | - George S D Gordon
- Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, CB2 0RE, UK
- Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK
| | - Sarah E Bohndiek
- Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK.
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, CB2 0RE, UK.
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Luthman AS, Waterhouse DJ, Ansel-Bollepalli L, Yoon J, Gordon GSD, Joseph J, di Pietro M, Januszewicz W, Bohndiek SE. Bimodal reflectance and fluorescence multispectral endoscopy based on spectrally resolving detector arrays. J Biomed Opt 2018; 24:1-14. [PMID: 30358334 PMCID: PMC6975231 DOI: 10.1117/1.jbo.24.3.031009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 09/07/2018] [Indexed: 05/08/2023]
Abstract
Emerging clinical interest in combining standard white light endoscopy with targeted near-infrared (NIR) fluorescent contrast agents for improved early cancer detection has created demand for multimodal imaging endoscopes. We used two spectrally resolving detector arrays (SRDAs) to realize a bimodal endoscope capable of simultaneous reflectance-based imaging in the visible spectral region and multiplexed fluorescence-based imaging in the NIR. The visible SRDA was composed of 16 spectral bands, with peak wavelengths in the range of 463 to 648 nm and full-width at half-maximum (FWHM) between 9 and 26 nm. The NIR SRDA was composed of 25 spectral bands, with peak wavelengths in the range 659 to 891 nm and FWHM 7 to 15 nm. The spectral endoscope design was based on a "babyscope" model using a commercially available imaging fiber bundle. We developed a spectral transmission model to select optical components and provide reference endmembers for linear spectral unmixing of the recorded image data. The technical characterization of the spectral endoscope is presented, including evaluation of the angular field-of-view, barrel distortion, spatial resolution and spectral fidelity, which showed encouraging performance. An agarose phantom containing oxygenated and deoxygenated blood with three fluorescent dyes was then imaged. After spectral unmixing, the different chemical components of the phantom could be successfully identified via majority decision with high signal-to-background ratio (>3). Imaging performance was further assessed in an ex vivo porcine esophagus model. Our preliminary imaging results demonstrate the capability to simultaneously resolve multiple biological components using a compact spectral endoscopy system.
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Affiliation(s)
- A. Siri Luthman
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
- University of Cambridge, Cancer Research UK Cambridge Institute, Li Ka Shing Center, Robinson Way, Cambridge, United Kingdom
| | - Dale J. Waterhouse
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
- University of Cambridge, Cancer Research UK Cambridge Institute, Li Ka Shing Center, Robinson Way, Cambridge, United Kingdom
| | - Laura Ansel-Bollepalli
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
- University of Cambridge, Cancer Research UK Cambridge Institute, Li Ka Shing Center, Robinson Way, Cambridge, United Kingdom
| | - Jonghee Yoon
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
- University of Cambridge, Cancer Research UK Cambridge Institute, Li Ka Shing Center, Robinson Way, Cambridge, United Kingdom
| | - George S. D. Gordon
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
- University of Cambridge, Department of Engineering, Cambridge, United Kingdom
| | - James Joseph
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
- University of Cambridge, Cancer Research UK Cambridge Institute, Li Ka Shing Center, Robinson Way, Cambridge, United Kingdom
| | - Massimiliano di Pietro
- University of Cambridge, MRC Cancer Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Wladyslaw Januszewicz
- University of Cambridge, MRC Cancer Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Sarah E. Bohndiek
- University of Cambridge, Department of Physics, Cambridge, United Kingdom
- University of Cambridge, Cancer Research UK Cambridge Institute, Li Ka Shing Center, Robinson Way, Cambridge, United Kingdom
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Macfaden AJ, Gordon GSD, Wilkinson TD. An optical Fourier transform coprocessor with direct phase determination. Sci Rep 2017; 7:13667. [PMID: 29057903 PMCID: PMC5651838 DOI: 10.1038/s41598-017-13733-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/25/2017] [Indexed: 11/09/2022] Open
Abstract
The Fourier transform is a ubiquitous mathematical operation which arises naturally in optics. We propose and demonstrate a practical method to optically evaluate a complex-to-complex discrete Fourier transform. By implementing the Fourier transform optically we can overcome the limiting O(nlogn) complexity of fast Fourier transform algorithms. Efficiently extracting the phase from the well-known optical Fourier transform is challenging. By appropriately decomposing the input and exploiting symmetries of the Fourier transform we are able to determine the phase directly from straightforward intensity measurements, creating an optical Fourier transform with O(n) apparent complexity. Performing larger optical Fourier transforms requires higher resolution spatial light modulators, but the execution time remains unchanged. This method could unlock the potential of the optical Fourier transform to permit 2D complex-to-complex discrete Fourier transforms with a performance that is currently untenable, with applications across information processing and computational physics.
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Affiliation(s)
- Alexander J Macfaden
- Centre of Molecular Materials for Photonics and Electronics, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK. .,Optalysys Ltd., Flemming Court, Whistler Drive, Glasshoughton, WF10 5HW, UK.
| | - George S D Gordon
- Centre of Molecular Materials for Photonics and Electronics, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
| | - Timothy D Wilkinson
- Centre of Molecular Materials for Photonics and Electronics, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK
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18
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Williams C, Bartholomew R, Rughoobur G, Gordon GSD, Flewitt AJ, Wilkinson TD. Fabrication of nanostructured transmissive optical devices on ITO-glass with UV1116 photoresist using high-energy electron beam lithography. Nanotechnology 2016; 27:485301. [PMID: 27811383 DOI: 10.1088/0957-4484/27/48/485301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
High-energy electron beam lithography for patterning nanostructures on insulating substrates can be challenging. For high resolution, conventional resists require large exposure doses and for reasonable throughput, using typical beam currents leads to charge dissipation problems. Here, we use UV1116 photoresist (Dow Chemical Company), designed for photolithographic technologies, with a relatively low area dose at a standard operating current (80 kV, 40-50 μC cm-2, 1 nAs-1) to pattern over large areas on commercially coated ITO-glass cover slips. The minimum linewidth fabricated was ∼33 nm with 80 nm spacing; for isolated structures, ∼45 nm structural width with 50 nm separation. Due to the low beam dose, and nA current, throughput is high. This work highlights the use of UV1116 photoresist as an alternative to conventional e-beam resists on insulating substrates. To evaluate suitability, we fabricate a range of transmissive optical devices, that could find application for customized wire-grid polarisers and spectral filters for imaging, which operate based on the excitation of surface plasmon polaritons in nanosized geometries, with arrays encompassing areas ∼0.25 cm2.
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Affiliation(s)
- Calum Williams
- Electrical Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK
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Kaczorowski A, Gordon GSD, Wilkinson TD. Adaptive, spatially-varying aberration correction for real-time holographic projectors. Opt Express 2016; 24:15742-56. [PMID: 27410846 DOI: 10.1364/oe.24.015742] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A method of generating an aberration- and distortion-free wide-angle holographically projected image in real time is presented. The target projector is first calibrated using an automated adaptive-optical mechanism. The calibration parameters are then fed into the hologram generation program, which applies a novel piece-wise aberration correction algorithm. The method is found to offer hologram generation times up to three orders of magnitude faster than the standard method. A projection of an aberration- and distortion-free image with a field of view of 90x45 degrees is demonstrated. The implementation on a mid-range GPU achieves high resolution at a frame rate up to 12fps. The presented methods are automated and can be performed on any holographic projector.
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Gordon GSD, Joseph J, Bohndiek SE, Wilkinson TD. Single-pixel phase-corrected fiber bundle endomicroscopy with lensless focussing capability. J Lightwave Technol 2015; 33:3419-3425. [PMID: 27279676 PMCID: PMC4894463 DOI: 10.1109/jlt.2015.2436816] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this paper a novel single-pixel method for coherent imaging through an endoscopic fiber bundle is presented. The use of a single-pixel detector allows greater sensitivity over a wider range of wavelengths, which could have significant applications in endoscopic fluorescence microscopy. First, the principle of lensless focussing at the distal end of a coherent fiber bundle is simulated to examine the impact of pixelation at microscopic scales. Next, an experimental optical correlator system using spatial light modulators (SLMs) is presented. A simple contrast imaging method of characterizing and compensating phase aberrations introduced by fiber bundles is described. Experimental results are then presented showing that our phase compensation method enables characterization of the optical phase profile of individual fiberlets. After applying this correction, early results demonstrating the ability of the system to electronically adjust the focal plane at the distal end of the fiber bundle are presented. The structural similarity index (SSIM) between the simulated image and the experimental focus-adjusted image increases noticeably when the phase correction is applied and the retrieved image is visually recognizable. Strategies to improve image quality are discussed.
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Affiliation(s)
- George S D Gordon
- Electrical Engineering Division, University of Cambridge, CB3 0FA, Cambridge, U.K.
| | - James Joseph
- Department of Physics and Cancer Research UK Cambridge Institute, University of Cambridge and CRUK-EPSRC Cancer Imaging Centre in Cambridge and Manchester
| | - Sarah E Bohndiek
- Department of Physics and Cancer Research UK Cambridge Institute, University of Cambridge and CRUK-EPSRC Cancer Imaging Centre in Cambridge and Manchester
| | - Timothy D Wilkinson
- Electrical Engineering Division, University of Cambridge, CB3 0FA, Cambridge, U.K
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Gordon GSD, Feng F, Kang Q, Jung Y, Sahu J, Wilkinson T. Coherent, focus-corrected imaging of optical fiber facets using a single-pixel detector. Opt Lett 2014; 39:6034-6037. [PMID: 25361149 DOI: 10.1364/ol.39.006034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A novel imaging technique that produces accurate amplitude and phase images of an optical fiber facet using only a phase-only liquid-crystal on silicon (LCOS) spatial light modulator (SLM) and a single-pixel detector is presented. The system can take images in two orthogonal polarizations and so provides a powerful tool for modal characterization of multimode fibers, which is of increasing importance due to their burgeoning use in telecommunications and medical applications. This technique first uses a simulated annealing algorithm to compute a hologram that collects light from a small region of the fiber facet. Next, the fiber facet is automatically brought into focus using adaptive aberration correction on the SLM. Finally, a common-path interferometer is created using the SLM, and the phase of the optical field at each pixel is determined. Finally, high-definition amplitude and phase images of a ring-core refractive index fiber are presented as a proof-of-principle demonstration of the technique.
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