1. Articles from Shoude Chang

    1-23 of 23
    1. Full Range Swept-Source Optical Coherence Tomography with Ultra Small Fiber Probes for Biomedical Imaging (Book Chapter)

      Full Range Swept-Source Optical Coherence Tomography with Ultra Small Fiber Probes for Biomedical Imaging (Book Chapter)

      Biomedical imaging is becoming an indispensable branch within bioengineering. This research field has recently expanded due to the requirement of high-level medical diagnostics and rapid development of interdisciplinary modern technologies. This book is designed to present the most recent advances in instrumentation, methods, and image processing as well as clinical applications in important areas of biomedical imaging. It provides broad coverage of the field of biomedical imaging, with particular attention to an engineering viewpoint. The goal of the book is to provide a wide-ranging forum in the biomedical imaging field that integrates interdisciplinary research and development of interest to scientists ...

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    2. Optical catheter with rotary optical cap

      Optical catheter with rotary optical cap

      A scanning optical head for a catheter is locally controlled by a motor at an insertion end of the catheter uses a hollow motor through which a longitudinal optical path of the catheter passes. This permits the motor to be positioned between a control base of the catheter and avoids rotating the whole fiber, and therefore makes the beam scanning stable and accurate. In addition, because there is no coupling component, it also eliminates the light reflection between additional surfaces as well as varying fiber birefringence, which becomes a cause of noise when imaging the deep structure.

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    3. Stationary-fiber rotary probe with unobstructed 360° view for optical coherence tomography

      Stationary-fiber rotary probe with unobstructed 360° view for optical coherence tomography
      A side-scanning fiber probe is a critical component for optical coherence tomography in medical imaging and diagnosis. We propose and fabricate an on-axis rotating probe that performs in situ, circumferential scanning that is shadow-free (not susceptible to shadow effects caused by the motor’s wires). A miniature motor that incorporates a bored-out shaft for the optical fiber is located at the distal end of the probe, which results in a more stable and uniform circumferential scan, free from wire-shadow interference effects. More importantly, this design, novel to our knowledge, compared to other probes avoids the insertion losses introduced by optical ...
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    4. Dual-Source Swept-Source Optical Coherence Tomography Reconstructed on Integrated Spectrum

      Dual-Source Swept-Source Optical Coherence Tomography Reconstructed on Integrated Spectrum
      Dual-source swept-source optical coherence tomography (DS-SSOCT) has two individual sources with different central wavelengths, linewidth, and bandwidths. Because of the difference between the two sources, the individually reconstructed tomograms from each source have different aspect ratio, which makes the comparison and integration difficult. We report a method to merge two sets of DS-SSOCT raw data in a common spectrum, on which both data have the same spectrum density and a correct separation. The reconstructed tomographic image can seamlessly integrate the two bands of OCT data together. The final image has higher axial resolution and richer spectroscopic information than any of ...
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    5. Optical coherence tomography: fundamental principles, instrumental designs and biomedical applications

      Optical coherence tomography: fundamental principles, instrumental designs and biomedical applications
      The advances made in the last two decades in interference technologies, optical instrumentation, catheter technology, optical detectors, speed of data acquisition and processing as well as light sources have facilitated the transformation of optical coherence tomography from an optical method used mainly in research laboratories into a valuable tool applied in various areas of medicine and health sciences. This review paper highlights the place occupied by optical coherence tomography in relation to other imaging methods that are used in medical and life science areas such as ophthalmology, cardiology, dentistry and gastrointestinal endoscopy. Together with the basic principles that lay behind ...
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    6. Simultaneous dual-wavelength-band common-path swept-source optical coherence tomography with single polygon mirror scanner

      Simultaneous dual-wavelength-band common-path swept-source optical coherence tomography with single polygon mirror scanner
      We report a novel (to the best of our knowledge) simultaneous 1310/1550 two-wavelength band swept laser source and dual-band common-path swept-source optical coherence tomography (SS-OCT). Synchronized dual-wavelength tuning is performed by using two laser cavities and narrowband wavelength filters with a single dual-window polygonal scanner. Measured average output powers of 60 and 27 mW have been achieved for the 1310 and 1550 nm bands, respectively, while the two wavelengths were swept simultaneously from 1227 to 1387 nm for the 1310 nm band and from 1519 to 1581 nm for the 1550 nm band at an A-scan rate of 65 ...
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    7. Performance analysis of a swept-source optical coherence tomography system with a quadrature interferometer and optical amplification

      Performance analysis of a swept-source optical coherence tomography system with a quadrature interferometer and optical amplification
      A performance analysis of signal to noise ratio for an optical coherence tomography system with quadrature detection and a semiconductor optical amplifier in the sample arm is discussed. The results are compared and discussed in relation to a conventional OCT system (without optical amplification). An increase of the signal to noise ratio up to 14 dB at a depth of 0.5 mm is obtained compared to the system without the optical amplifier. Overall, an improvement was demonstrated for signal coming from deeper regions within the samples. Arterial plaque from a myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbit is visualized ...
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    8. Optical coherence tomography used for jade industry

      Optical coherence tomography used for jade industry
      As an expensive natural stone, jade has a worldwide market. In the jade industry, the inspection and analysis basically rely on the human eye and/or experience, which cause unavoidable waste and damage of these expensive materials. Optical Coherence Tomography (OCT) is a fundamentally new type of optical sensing technology, which can perform high resolution, cross-sectional sensing of the internal structure of materials. As jade is almost translucent to infra red light, OCT becomes an ideal tool to change the traditional procedure to volume data based machine vision system. OCT can also be used for anti-counterfeit of the expensive jade ...
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    9. Signal attenuation and box-counting
fractal analysis of optical coherence
tomography images of arterial tissue

      Signal attenuation and box-counting
fractal analysis of optical coherence
tomography images of arterial tissue
      The sensitivity of optical coherence tomography images to sample morphology is tested by two methods. The first method estimates the attenuation of the OCT signal from various regions of the probed tissue. The second method uses a box-counting algorithm to calculate the fractal dimensions in the regions of interest identified in the images. Although both the attenuation coefficient as well as the fractal dimension correlate very well with the anatomical features of the probed samples; the attenuation method provides a better sensitivity. Two types of samples are used in this study: segments of arteries collected from atherosclerosis–prone Watanabe rabbits ...
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    10. Jade detection and analysis based on optical coherence tomography images

      Jade detection and analysis based on optical coherence tomography images
      Optical coherence tomography is a fundamentally new type of optical sensing technology that can perform high-resolution, cross sectional sensing of the internal structure of materials and biological samples. This work briefly describes its capability of exploring and analyzing the internal structures and textures of various jades. With a depth resolution of 4 µm in jade and penetration range of 5 mm in jade, swept-source OCT could be used as a new powerful instrument to generate 3-D volume data of jade, which is important for applications in jade industry and artwork, particularly for jade detection and classification, counterfeit recognition, and guided ...
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    11. Extracting information from optical coherence tomography images of tissues: signal attenuation and fractal analysis of speckle pattern

      Extracting information from optical coherence tomography images of tissues: signal attenuation and fractal analysis of speckle pattern
      Two methods for analyzing OCT images of arterial tissues are tested. These methods are applied toward two types of samples: segments of arteries collected from atherosclerosis-prone Watanabe heritable hyper-lipidemic rabbits and pieces of porcine left descending coronary arteries without atherosclerosis. The first method is based on finding the attenuation coefficients for the OCT signal that propagates through various regions of the tissue. The second method involves calculating the fractal dimensions of the OCT signal textures in the regions of interest identified within the acquired images. A box-counting algorithm is used for calculating the fractal dimensions. Both parameters, the attenuation coefficient ...
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    12. New optical instruments for coherence tomography

      We present the following novel technologies for optical coherence tomography developed in Institute for Microstructural Sciences, National Research Council Canada. We first demonstrate a high power mode-lock wavelength swept laser using a polygon-based narrowband optical scanning filter first. Peak and average output powers of 98 mW and 71 mW have been achieved, respectively, without an external amplifier, while the wavelength was swept continuously from 1247 nm to 1360 nm. Then, we present a design, construction and characterization of ultra-small OCT probes using fiber lenses. Those fiber lens modules are made of a single mode fiber and a GRIN or ball ...
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    13. Complex swept source optical coherence tomography with ultra-small fiber probe for biomedical imaging

      We demonstrate a catheter-based complex swept-source optical coherence tomography (SS-OCT) system using a 3x3 Mach-Zehnder quadrature interferometer and an ultra-small optic probe. Design and fabrication of fiber lens for ultrasmall optic probes are presented first. We compare in detail measured performance with expected theoretical performance. Then, we present a 3x3 Mach-Zehnder quadrature interferometer to acquire a complex interferometric signal for SS-OCT. We introduce an unbalanced differential detection method to improve the overall utilization of optical power and provide simultaneous access to the complementary phase components of the complex interferometric signal. No calculations by trigonometric relationships are needed. We compare the ...
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    14. Quantitative analysis of arterial tissue with optical coherence tomography

      Tissue morphology, light attenuation and texture are analyzed from images acquired by swept-source Fourier-domain optical coherence tomography from arterial samples. The data were corrected for the effect of the confocal point spread function and were analyzed using the single scattering model.
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    15. Interferometric system for complex image extraction

      The invention provides an interferometric system and method for quadrature detection of optical characteristics of a sample. The system includes a Mach-Zehnder interferometer providing a variable optical delay between light collected from the sample and reference light. The Mach-Zehnder interferometer has an output M.times.N coupler with N.gtoreq.3 output ports. Two differential detectors, each having two input ports coupled to a different two of the N output ports of the M.times.N coupler, produce first and second electrical signals having an interferometric phase shift. A processor is provided for computing real and imaginary parts of a ...
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    16. High-power 1300 nm FDML swept laser using polygon-based narrowband optical scanning filter

      Swept-source optical coherence tomography (SS-OCT) has received much attention in recent years because of its higher sensitivity in high speed imaging. A fast and high powered wavelength-swept laser is important for SS-OCT since its speed and sensitivity directly rely on the sweeping rate and the ou ... [Proc. SPIE 7168, 716822 (2009)] published Fri Feb 20, 2009.
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    17. Optical coherence tomography: technology and applications

      Optical coherence tomography (OCT) has recently emerged as a powerful optical imaging instrument and technology. OCT performs high resolution, cross-sectional tomographic imaging of the internal structure in 3D materials including biological tissues. Advantages of OCT vs. other imaging systems are: 1) High resolution: enables greater visualization of defects. (OCT: 5-10 microns, ultrasound: 150 microns. High resolution CT: 300 microns. MRI: 1,000 microns). 2) Noninvasive, non-contact: increase ease of use. 3) Fiber-optics delivery: allows OCT to be used in catheters and endoscopes. (Fiber diameter is normally 125 microns). 4) High speed: enables high-resolution 3D imaging. 5) Potential for additional information ...
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    18. 3×3 MZI with unbalanced differential detection for full range swept-source optical coherence tomography

      Quadrature interferometry based on 3×3 fiber couplers could be used to double the effective imaging depth in Swept- Source Optical Coherence Tomography. This is due to its ability to suppress the complex conjugate artifact naturally. We present theoretical and experimental results for a 3×3 Mach-Zehnder interferometer using a new unbalanced differential optical detection method. The new interferometer provides simultaneous access to complementary phase components of the complex interferometric signal. No calculations by trigonometric relationships are needed. We demonstrate a complex conjugate artifact suppression of 27 dB obtained in a swept-source optical coherence tomography using our unbalanced differential detection ...
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    19. Fiber probes used in optical coherence tomography

      Quality and parameters of probing optical beams are extremely important in optical coherence tomography (OCT) systems both for image quality and light coupling efficiency considerations. For example, the shape, size, focal position, and focal range of such beams could have a great impact on the lateral resolution, penetration depth, and signal-to-noise ratio of the image. We present a design, construction and characterization of different variations of GRIN and ball fiber lenses, for ultra-small OCT probes. Those fiber probes are made of a single mode fiber and a GRIN or ball fiber lens with or without a fiber spacer between them ...
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    20. 3×3 Mach-Zehnder interferometer with unbalanced differential detection for full-range swept-source optical coherence tomography

      Youxin Mao, Sherif Sherif, Costel Flueraru, Shoude Chang. Quadrature interferometry based on 3×3 fiber couplers could be used to double the effective imaging depth in swept-source optical coherence tomography. This is due to its ability to suppress the complex conjugate artifact naturally. We present theoretical and experimental results for a ... [Appl. Opt. 47, 2004-2010 (2008)]
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    21. Design and implementation of fiber lenses for ultra-small probes used in biomedical imaging

      Quality and parameters of probing optical beams are extremely important in biomedical imaging systems both for image quality and light coupling efficiency considerations. For example, the shape, size, focal position, and focal range of such beams could have a great impact on the lateral resolution, ... [Proc. SPIE Int. Soc. Opt. Eng. 6826, 68261A (2008)] published Tue Jan 8, 2008.
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    22. Statistics of the depth-scan photocurrent in time-domain optical coherence tomography

      We derive the time-variant second-order statistics of the depth-scan photocurrent in time-domain optical coherence tomography (TD-OCT) systems using polarized thermal light sources and superluminescent diodes (SLDs). Since the asymptotic-joint-probability-distribution function (JPDF) of the ... [J. Opt. Soc. Am. A 25, 16-20 (2008)]
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    23. Full-field optical coherence tomography and its application to multiple-layer information decoding

      A method of extracting a tomographic image of a layer within a body by optical coherence tomography, involves capturing three images, namely a non-interference background image, a first interference-fringe image of said layer, and a second interference-fringe image phase-shifted relative to the first interference-fringe image. The tomographic image is obtained by mathematically combining the three captured images. In a preferred embodiment random noise is removed by averaging and inter-layer effects are removed by applying a compensation function. This system is then used to extract the 2D cross-sectional images encoded in a multiple-layer information carrier.
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    1-23 of 23
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  2. Topics in the News

    1. (23 articles) National Research Council Canada
    2. (23 articles) Shoude Chang
    3. (22 articles) Costel Flueraru
    4. (21 articles) Youxin Mao
    5. (9 articles) Sherif S. Sherif
    6. (7 articles) University of Manitoba
    7. (5 articles) Dan P. Popescu
    8. (5 articles) Michael G. Sowa
    9. (2 articles) Guangming Chang
    10. (1 articles) Adrian G. Podoleanu
    11. (1 articles) Samsung
    12. (1 articles) Johns Hopkins University
    13. (1 articles) National Institutes of Health
    14. (1 articles) Sungkyunkwan University
    15. (1 articles) University of São Paulo
    16. (1 articles) Massachusetts Institute of Technology
    17. (1 articles) L V Prasad Eye Institute
    18. (1 articles) Gong Je Seong
    19. (1 articles) Chan Yun Kim
    20. (1 articles) James G. Fujimoto
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    Jade detection and analysis based on optical coherence tomography images Signal attenuation and box-counting
fractal analysis of optical coherence
tomography images of arterial tissue Optical coherence tomography used for jade industry Optical coherence tomography: fundamental principles, instrumental designs and biomedical applications Factors Associated with Changes in Retinal Layers Following Acute Optic Neuritis: A Longitudinal Study Using Optical Coherence Tomography Relationship between N95 Amplitude of Pattern Electroretinogram and Optical Coherence Tomography Angiography in Open-Angle Glaucoma Historic Effort to 'End Blindness" Marks a Major Milestone with Leading Scientist Recognized for Pioneering Work at VIP Ceremony Featuring Tribute to Ruth Bader Ginsburg Healing and early stent coverage after ultrathin strut biodegradable polymer‐coated sirolimus‐eluting stent implantation: SiBi optical coherence tomography study Influences of hypomagnesemia on optic nerve and retinal vascular structure determined using optical coherence tomography angiography Repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography in myopic and postphotorefractive keratectomy eyes Vessel Density around Foveal Avascular Zone as a Potential Imaging Biomarker for Detecting Preclinical Diabetic Retinopathy: An Optical Coherence Tomography Angiography Study Vascular risk factors for optical coherence tomography-detected macular cysts: The Maastricht Study