1. Articles from T. Joshua Pfefer

    1-7 of 7
    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. Three-dimensional printing of tissue phantoms for biophotonic imaging

      Three-dimensional printing of tissue phantoms for biophotonic imaging

      We have investigated the potential of tissue phantoms fabricated with thermosoftening- and photopolymerization-based three-dimensional (3D) printers for use in evaluation of biophotonic imaging systems. The optical properties of printed polymer samples were measured and compared to biological tissues. Phantoms with subsurface channels as small as 0.2 mm in diameter were fabricated and imaged with microscopy, x-ray microtomography, and optical coherence tomography to characterize morphology. These phantoms were then implemented to evaluate the penetration depth of a hyperspectral reflectance imaging system used in conjunction with a near-infrared contrast agent. Results indicated that 3D printing may provide a suitable platform for ...

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    4. Retina-simulating phantom for optical coherence tomography

      Retina-simulating phantom for optical coherence tomography

      Optical coherence tomography (OCT) is a rapidly growing imaging modality, particularly in the field of ophthalmology. Accurate early diagnosis of diseases requires consistent and validated imaging performance. In contrast to more well-established medical imaging modalities, no standardized test methods currently exist for OCT quality assurance. We developed a retinal phantom which mimics the thickness and near-infrared optical properties of each anatomical retinal layer as well as the surface topography of the foveal pit. The fabrication process involves layer-by-layer spin coating of nanoparticle-embedded silicone films followed by laser micro-etching to modify the surface topography. The thickness of each layer and dimensions ...

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    5. Multilayer thin-film phantoms for axial contrast transfer function measurement in optical coherence tomography

      Multilayer thin-film phantoms for axial contrast transfer function measurement in optical coherence tomography

      In optical coherence tomography (OCT), axial resolution is one of the most critical parameters impacting image quality. It is commonly measured by determining the point spread function (PSF) based on a specular surface reflection. The contrast transfer function (CTF) provides more insights into an imaging system’s resolving characteristics and can be readily generated in a system-independent manner, without consideration for image pixel size. In this study, we developed a test method for determination of CTF based on multi-layer, thin-film phantoms, evaluated using spectral- and time-domain OCT platforms with different axial resolution values. Phantoms representing six spatial frequencies were fabricated ...

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    6. Characterizing the point spread function of retinal OCT devices with a model eye-based phantom

      Characterizing the point spread function of retinal OCT devices with a model eye-based phantom

      We have designed, fabricated, and tested a nanoparticle-embedded phantom (NEP) incorporated into a model eye in order to characterize the point spread function (PSF) of retinal optical coherence tomography (OCT) devices in three dimensions under realistic imaging conditions. The NEP comprises a sparse distribution of highly backscattering silica-gold nanoshells embedded in a transparent UV-curing epoxy. The commercially-available model eye replicates the key optical structures and focusing power of the human eye. We imaged the model eye-NEP combination with a research-grade spectral domain OCT system designed for in vivo retinal imaging and quantified the lateral and axial PSF dimensions across the ...

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    7. Three-dimensional characterization of optical coherence tomography point spread functions with a nanoparticle-embedded phantom

      Three-dimensional characterization of optical coherence tomography point spread functions with a nanoparticle-embedded phantom
      We present a novel (to our knowledge) approach for measurement of the three-dimensional point spread function (PSF) of optical coherence tomography (OCT) systems using a nanoparticle-embedded phantom (NEP), toward development of standardized test methods for biophotonic imaging. The NEP comprises highly reflective plasmonic nanoparticles, homogeneously distributed in a transparent silicone matrix. OCT image volumes were analyzed to characterize PSFs in axial and lateral directions at a variety of locations in the NEP. Results indicate submicrometer agreement with conventional approaches to measure dimensions of the PSF. The NEP offers a robust approach for validating and comparing imaging performance of OCT devices.
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    1-7 of 7
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    1. (6 articles) FDA
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    Three-dimensional characterization of optical coherence tomography point spread functions with a nanoparticle-embedded phantom Characterizing the point spread function of retinal OCT devices with a model eye-based phantom Multilayer thin-film phantoms for axial contrast transfer function measurement in optical coherence tomography Retina-simulating phantom for optical coherence tomography Three-dimensional printing of tissue phantoms for biophotonic imaging Variations in optical coherence tomography resolution and uniformity: a multi-system performance comparison Methods to assess sensitivity of optical coherence tomography systems Full-range space-division multiplexing optical coherence tomography angiography Measuring 3D Optic Nerve Head Deformations using Digital Volume Correlation of in vivo Optical Coherence Tomography Data (Thesis) Optical coherence tomography for characterization of nanocomposite materials (Thesis) In Vivo Corneal Microstructural Changes in Herpetic Stromal Keratitis: A Spectral-Domain Optical Coherence Tomography Analysis Non-invasive optical screening of Streptococcus Pneumonia based inflammatory changes of the tympanic membrane and mastoid mucosa in guinea pig otitis media using optical coherence tomography