1. Articles from Peter D. Woolliams

    1-10 of 10
    1. Methods to assess sensitivity of optical coherence tomography systems

      Methods to assess sensitivity of optical coherence tomography systems

      Measuring the sensitivity of an optical coherence tomography (OCT) system determines the minimum sample reflectivity it can detect and provides a figure of merit for system optimization and comparison. The published literature lacks a detailed description of OCT sensitivity measurement procedures. Here we describe a commonly-used measurement method and introduce two new phantom-based methods, which also offer a means to directly visualize low reflectivity conditions relevant to biological tissue. We provide quantitative results for the three methods from different OCT system configurations and discuss the methods’ advantages and disadvantages.

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    2. Variations in optical coherence tomography resolution and uniformity: a multi-system performance comparison

      Variations in optical coherence tomography resolution and uniformity: a multi-system performance comparison

      Point spread function (PSF) phantoms based on unstructured distributions of sub-resolution particles in a transparent matrix have been demonstrated as a useful tool for evaluating resolution and its spatial variation across image volumes in optical coherence tomography (OCT) systems. Measurements based on PSF phantoms have the potential to become a standard test method for consistent, objective and quantitative inter-comparison of OCT system performance. Towards this end, we have evaluated three PSF phantoms and investigated their ability to compare the performance of four OCT systems. The phantoms are based on 260-nm-diameter gold nanoshells, 400-nm-diameter iron oxide particles and 1.5-micron-diameter silica ...

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    3. Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription

      Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription

      Optical coherence tomography (OCT) is a non-invasive three-dimensional imaging system that is capable of producing high resolution in-vivo images. OCT is approved for use in clinical trials in Japan, USA and Europe. For OCT to be used effectively in a clinical diagnosis, a method of standardisation is required to assess the performance across different systems. This standardisation can be implemented using highly accurate and reproducible artefacts for calibration at both installation and throughout the lifetime of a system. Femtosecond lasers can write highly reproducible and highly localised micro-structured calibration artefacts within a transparent media. We report on the fabrication of ...

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    4. Feature Of The Week 1/8/12: Ultrafast Processing and Rendering of OCT Data using a GPU

      Feature Of The Week 1/8/12: Ultrafast Processing and Rendering of OCT Data using a GPU
      Processing of the large volumetric data is the bottleneck of the current FD-OCT systems. Solving this issue enables real time visualisation. Various groups have applied utilising the full power of GPU for OCT data processing allows to realise the full potential of OCT. GPU based data processing to OCT. Here we present a GPU-CPU based processing methodology as well evaluates the performance of various GPUs.In standard processing, interference data are copied to GPU and entire computation is carried out on GPU. Processed data are stored in GPU memory, which allows rendering and visualising the data.To benchmark the processing ...
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    5. Estimating the resolution of a commercial optical coherence tomography system with limited spatial sampling

      Estimating the resolution of a commercial optical coherence tomography system with limited spatial sampling
      Optical coherence tomography (OCT) is becoming increasingly widespread as an experimental tool for clinical investigation, facilitated by the development of commercial instruments. In situ performance evaluation of such 'black box' systems presents a challenge, where the instrument hardware and software can limit access to important configuration parameters and raw data. Two key performance metrics for imaging systems are the point-spread function (PSF) and the associated modulation transfer function (MTF). However, previously described experimental measurement techniques assume user-variable spatial sampling and may not be appropriate for the characterization of deployed commercial instruments. Characterization methods developed for other modalities do not address ...
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    6. Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts

      Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts
      Optical coherence tomography (OCT) systems are becoming more commonly used in biomedical imaging and, to enable continued uptake, a reliable method of characterizing their performance and validating their operation is required. This paper outlines the use of femtosecond laser subsurface micro-inscription techniques to fabricate an OCT test artifact for validating the resolution performance of a commercial OCT system. The key advantage of this approach is that by utilizing the nonlinear absorption a three dimensional grid of highly localized point and line defects can be written in clear fused silica substrates.
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    7. Spatially deconvolved optical coherence tomography

      Spatially deconvolved optical coherence tomography
      In this paper we present spatially mapped point-spread function (PSF) measurements of an optical coherence tomography (OCT) instrument and subsequent spatial deconvolution. The OCT B-scan image plane was divided into 2400 subimages, for which PSFs were determined from OCT measurements of a specially designed phantom. Each PSF was deconvolved from its corresponding subimage of the phantom using the Lucy-Richardson algorithm. Following deconvolution, all of the subimages were reassembled to form a final deconvolved image, from which the resolution improvement was quantitatively assessed. The lateral resolution was found to improve by 3.1 μm compared to an axial resolution enhancement of ...
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    8. Contrast phantoms for optical coherence tomography

      Contrast phantoms for optical coherence tomography
      In this work we present contrast measurement phantoms for optical coherence tomography. In this initial study, contrast has been evaluated from OCT images of a USAF-1951 bar target, buried beneath scattering layers of different density. Preliminary results indicate that scattering does not degrade imaging contrast significantly, however further work is required to verify these findings. This work has important implications from a quality control perspective as well for OCT inter-comparisons at, for example, different wavebands.
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    9. Report on Optical Tissue Phantoms from National Physical Laboratory in UK

      Report on Optical Tissue Phantoms from National Physical Laboratory in UK
      The key figures of merit for Optical Coherence Tomography (OCT) systems are sensitivity and resolution. These parameters can be used to determine the suitability of instruments for purpose and to gauge the practical improvements to instruments afforded by modifications to the design. Therefore, NPL is developing reproducible and stable phantoms for depth resolved sensitivity and three-dimensional resolution or point-spread-function (PSF
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    10. Point-spread function phantoms for optical coherence tomography

      Point-spread function phantoms for optical coherence tomography
      Recently scientists at the Uk's National Physical Laboratory completed an initial study into the development of robust point-spread function (PSF) phantoms, that are potentially suitable as OCT calibration standards. The findings have been published in a publicly available NPL report, available freely from the NPL website or upon request to Pete Tomlins (pete.tomlins@npl.co.uk).
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    1-10 of 10
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  2. Topics in the News

    1. (10 articles) Peter D. Woolliams
    2. (9 articles) UK National Physical Laboratory
    3. (9 articles) Pete H. Tomlins
    4. (3 articles) Janarthanan Rasakanthan
    5. (3 articles) Kate Sugden
    6. (2 articles) University of London
    7. (2 articles) FDA
    8. (2 articles) Anant Agrawal
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    Point-spread function phantoms for optical coherence tomography Report on Optical Tissue Phantoms from National Physical Laboratory in UK Contrast phantoms for optical coherence tomography Spatially deconvolved optical coherence tomography Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts Estimating the resolution of a commercial optical coherence tomography system with limited spatial sampling Feature Of The Week 1/8/12: Ultrafast Processing and Rendering of OCT Data using a GPU Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription Variations in optical coherence tomography resolution and uniformity: a multi-system performance comparison Methods to assess sensitivity of optical coherence tomography systems Direct inverse linearization of piezoelectric actuator’s initial loading curve and its applications in full-field optical coherence tomography (FF-OCT) Peripapillary Retinal and Choroidal Perfusion in Nonarteritic Ischemic Optic Neuropathy Using Optical Coherence Tomography Angiography