1. Articles from Peter Woolliams

    1-6 of 6
    1. Multi-system comparison of optical coherence tomography performance with point spread function phantoms

      Multi-system comparison of optical coherence tomography performance with point spread function phantoms

      Point spread function (PSF) phantoms based on unstructured distributions of sub-resolution particles in a transparent matrix have proven effective for evaluating resolution and its spatial variation 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, submicron-diameter iron oxide particles and 1.5-micron-diameter silica particles. The OCT systems included spectral-domain and ...

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    2. Three-dimensional calibration targets for optical coherence tomography

      Three-dimensional calibration targets for optical coherence tomography

      The recent expansion of clinical applications for optical coherence tomography (OCT) is driving the development of approaches for consistent image acquisition. There is a simultaneous need for time-stable, easy-to-use imaging targets for calibration and standardization of OCT devices. We present calibration targets consisting of three-dimensional structures etched into nanoparticle-embedded resin. Spherical iron oxide nanoparticles with a predominant particle diameter of 400 nm were homogeneously dispersed in a two part polyurethane resin and allowed to harden overnight. These samples were then etched using a precision micromachining femtosecond laser with a center wavelength of 1026 nm, 100kHz repetition rate and 450 fs ...

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    3. Elastographic contrast generation in optical coherence tomography from a localized shear stress

      Elastographic contrast generation in optical coherence tomography from a localized shear stress
      A technique for generating contrast in two-dimensional shear strain elastograms from a localized stress is presented. The technique involves generating a non-uniform, localized stress via a magnetically actuated implant. Its effectiveness is demonstrated using finite-element simulations and a phantom study provides experimental verification of this. The method is applied to a superficial cancerous lesion model represented as a stiff inclusion in normal tissue. The lesion was best distinguished from its surroundings using total shear strain elastograms, rather than individual strain components. In experimental phantom studies, the lesion was imaged using optical coherence tomography (OCT) and could still be distinguished in ...
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    4. Refractive index mapping of layered samples using optical coherence refractometry

      In this paper a novel method for determining refractive indices of a multi-layered samples using low coherence interferometry (LCI), developed at the National Physical Laboratory, UK, is introduced. Conventional Optical Coherence Tomography (OCT) utilises a lateral scanning optical probe beam to construct a depth resolved image of the sample under investigation. All interfaces are detected in optical path length, resulting in an image depending on the refractive index of all prior layers. This inherent ambiguity in optical and geometric path length reduces OCT images to purely qualitative ones. We have demonstrated that by optically probing the sample at multiple angles ...
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    5. Optical coherence refractometry

      Peter H. Tomlins, Peter Woolliams, Christian Hart, Andrew Beaumont, Matthew Tedaldi We introduce a novel approach to refractometry using a low coherence interferometer at multiple angles of incidence. We show that for plane parallel samples it is possible to measure their phase refractive index rather than the group index that is usually measured by interferometric methods. This ... [Opt. Lett. 33, 2272-2274 (2008)]
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    6. Measurement of the three-dimensional point-spread function in an optical coherence tomography imaging system

      Peter H. Tomlins, Peter Woolliams, Matthew Tedaldi et al. Two significant figures of merit for optical coherence tomography (OCT) systems are the axial and transverse resolutions. Transverse resolution has been defined using the Rayleigh Criterion or from Gaussian beam optics. The axial resolution is generally defined in terms of the coherence length of a ... [Proc. SPIE Int. Soc. Opt. Eng. 6847, 68472Q (2008)] published Mon Feb 18, 2008.
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    1-6 of 6
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  2. Topics in the News

    1. (6 articles) Peter D. Woolliams
    2. (6 articles) Pete H. Tomlins
    3. (5 articles) UK National Physical Laboratory
    4. (3 articles) Matthew Tedaldi
    5. (2 articles) University of London
    6. (1 articles) Rice University
    7. (1 articles) Chao-Wei Chen
    8. (1 articles) Anant Agrawal
    9. (1 articles) Yu Chen
    10. (1 articles) Michelson Diagnostics
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    Elastographic contrast generation in optical coherence tomography from a localized shear stress Three-dimensional calibration targets for optical coherence tomography Multi-system comparison of optical coherence tomography performance with point spread function phantoms Evaluation of Age-related Skin Changes and Instrument Reliability Using Clinical Probe Measurements and Imaging Modalities HP-OCT™ wins Victorian AEEA award – nominated for Sir William Hudson award Postdoctoral Scholar in High Resolution Retinal Imaging at The Ohio State University Cone Photoreceptor Integrity assessed with Adaptive Optics Imaging after Laser-Pointer-Induced Retinal Injury Quantitative assessment of macular microvasculature and radial peripapillary capillary plexus in the fellow eyes of patients with retinal vein occlusion using OCT angiography Identification of the type of stent with three-dimensional optical coherence tomography: the SPQR study Serial optical coherence tomography findings after drug-coated balloon treatment in de novo coronary bifurcation lesion Serial optical coherence tomography for characterization of coronary lithotripsy efficacy: How much is enough? Application of optical frequency domain imaging to recanalized unruptured internal carotid artery aneurysm treated by flow-diverting stent-assisted coiling