Articles from opticsinfobase.org

1. Measurement of signal intensity depth profiles in rat brains with cardiac arrest maintaining primary temperature by wide-field optical coherence tomography

   Explore Article opticsinfobase.org (Aug 31 2010) Neurology

   We have already reported that after an injection for euthanasia, the signal intensity of optical coherence tomography (OCT) images are 2.7 times increased before cardiac arrest (CA) using OCT and rat brains without temperature control to show the potential of OCT to monitor tissue viability in brains [Appl. Opt. 48, 4354 (2009)]. In this paper, we similarly measured maintaining the primary temperature of rat brains. It was confirmed that when maintaining the primary temperature, the time courses of the ratios of signal intensity (RSIs) were almost the same as those without temperature control. RSIs after CA varied from 1.6 to ... (Read Full Article)
   

   Comment on Article Mentions:   Manabu Sato   Yamagata University

2. Automatic segmentation of seven retinal layers in SDOCT images congruent with expert manual segmentation

   Explore Article opticsinfobase.org (Aug 27 2010) Ophthalmology

   Stephanie J. Chiu, , Peter Nicholas, Cynthia A. Toth, Joseph A. Izatt, Sina FarsiuSegmentation of anatomical and pathological structures in ophthalmic images is crucial for the diagnosis and study of ocular diseases. However, manual segmentation is often a time-consuming and subjective process. This paper presents an automatic approach for segmenting retinal layers in Spectral ... [Opt. Express 18, 19413-19428 (2010)] (Read Full Article)
   

   Comment on Article Mentions:   Cynthia A. Toth   Joseph A. Izatt   Duke University

3. Real-time processing for full-range Fourier-domain optical-coherence tomography with zero-filling interpolation using multiple graphic processing units

   Explore Article opticsinfobase.org (Aug 26 2010)

   The real-time display of full-range, 2048 axial pixel×1024 lateral pixel, Fourier-domain optical-coherence tomography (FD-OCT) images is demonstrated. The required speed was achieved by using dual graphic processing units (GPUs) with many stream processors to realize highly parallel processing. We used a zero-filling technique, including a forward Fourier transform, a zero padding to increase the axial data-array size to 8192, an inverse-Fourier transform back to the spectral domain, a linear interpolation from wavelength to wavenumber, a lateral Hilbert transform to obtain the complex spectrum, a Fourier transform to obtain the axial profiles, and a log scaling. The data-transfer time of the ... (Read Full Article)
   

   Comment on Article Mentions:   Yuuki Watanabe   Yamagata University

4. Detection of early colorectal cancer development in the azoxymethane rat carcinogenesis model with Fourier domain low coherence interferometry

   Explore Article opticsinfobase.org (Aug 25 2010) Oncology

   Fourier domain low coherence interferometry (fLCI) is an emerging optical technique used to quantitatively assess cell nuclear morphology in tissue as a means of detecting early cancer development. In this work, we use the azoxymethane rat carcinogenesis model, a well characterized and established model for colon cancer research, to demonstrate the ability of fLCI to distinguish between normal and preneoplastic ex-vivo colon tissue. The results show highly statistically significant differences between the measured cell nuclear diameters of normal and azoxymethane-treated tissues, thus providing strong evidence that fLCI may be a powerful tool for non-invasive, quantitative detection of early changes associated ... (Read Full Article)
   

   Comment on Article Mentions:   Francisco E. Robles   Yizheng Zhu   Duke University

5. >400 kHz repetition rate wavelength-swept laser and application to high-speed optical frequency domain imaging

   Explore Article opticsinfobase.org (Aug 23 2010) Tunable Sources

   We demonstrate a high-speed wavelength-swept laser with a tuning range of 104nm (1228–1332nm) and a repetition rate of 403kHz. The design of the laser utilizes a high-finesse polygon-based wavelength-scanning filter and a short-length unidirectional ring resonator. Optical frequency domain imaging of the human skin in vivo is presented using this laser, and the system shows sensitivity of higher than 98dB with single-side ranging depth of 1.7mm over 4dB sensitivity roll-off. (Read Full Article)
   

   Comment on Article Mentions:   Wang Yuhl Oh   Benjamin J. Vakoc   Milen Shishkov

6. Separating the scattering and absorption coefficients using the real and imaginary parts of the refractive index with low-coherence interferometry

   Explore Article opticsinfobase.org (Aug 16 2010)

   We present an analytical method that yields the real and imaginary parts of the refractive index (RI) from low-coherence interferometry measurements, leading to the separation of the scattering and absorption coefficients of turbid samples. The imaginary RI is measured using time-frequency analysis, with the real part obtained by analyzing the nonlinear phase induced by a sample. A derivation relating the real part of the RI to the nonlinear phase term of the signal is presented, along with measurements from scattering and nonscattering samples that exhibit absorption due to hemoglobin. (Read Full Article)
   

   Comment on Article Mentions:   Francisco E. Robles   Adam Wax   Duke University

7. Doppler imaging with dual-detection full-range frequency domain optical coherence tomography

   Explore Article opticsinfobase.org (Aug 10 2010) Doppler

   Most of full-range techniques for Frequency Domain Optical Coherence Tomography (FD-OCT) reported to date utilize the phase relation between consecutive axial lines to reconstruct a complex interference signal and hence may exhibit degradation in either mirror image suppression performance or detectable velocity dynamic range or both when monitoring a moving sample such as flow activity. We have previously reported a technique of mirror image removal by simultaneous detection of the quadrature components of a complex spectral interference called a Dual-Detection Frequency Domain OCT (DD-FD-OCT) [Opt. Lett. 35, 1058-1060 (2010)]. The technique enables full range imaging without any loss of acquisition ... (Read Full Article)
   

   Comment on Article Mentions:   Jannick P. Rolland   Panomsak Meemon   Kye-Sung Lee

8. An automatic image processing algorithm for initiating and terminating intracoronary OFDI pullback

   Explore Article opticsinfobase.org (Aug 10 2010) Cardiology

   Intracoronary optical frequency domain imaging (OFDI) provides high resolution, three-dimensional views of coronary artery microstructure, but requires a non-occlusive saline/contrast purge to displace blood for clear artery views. Recent studies utilized manual pullback initiation/termination based on real-time image observation. Automated pullback initiation/termination by real-time OFDI signal analysis would enable more efficient data acquisition. We evaluate the use of simple imaging parameters to automatically and robustly differentiate between diagnostic-quality clear artery wall (CAW) versus blood-obstructed fields (BOF). Algorithms are tested using intracoronary OCT human data retrospectively and intracoronary OFDI swine and human data prospectively. In prospective analysis of OFDI swine data, ... (Read Full Article)
   

   Comment on Article Mentions:   Melissa J. Suter   Sergio Waxman   Benjamin J. Vakoc

9. Assessing hemoglobin concentration using spectroscopic optical coherence tomography for feasibility of tissue diagnostics

   Explore Article opticsinfobase.org (Aug 3 2010)

   Hemoglobin (Hb) concentration and oxygen saturation levels are important biomarkers for various diseases, including cancer. Here, we investigate the ability to measure these parameters for tissue using spectroscopic optical coherence tomography (SOCT). A parallel frequency domain OCT system is used with detection spanning the visible region of the spectrum (450 nm to 700 nm). Oxygenated and deoxygenated Hb absorbing phantoms are analyzed. The results show that Hb concentrations as low as 1.2 g/L at 1 mm can be retrieved indicating that both normal and cancerous tissue measurements may be obtained. However, measurement of oxygen saturation levels may not be achieved ... (Read Full Article)
   

   Comment on Article Mentions:   Duke University   Adam Wax   Francisco E. Robles

10. Efficient and facile delivery of gold nanoparticles in vivo using dissolvable microneedles for contrast-enhanced optical coherence tomography

    Explore Article opticsinfobase.org (Aug 3 2010)

    Obtaining sufficient contrast is an indispensable requirement for detecting early stage cancer using optical coherence tomography (OCT), an emerging diagnostic tool that detects abnormal lesions with micrometer resolutions in real time. PEGylated gold nanoparticles (Au NPs; 87 nm in diameter) were formulated in aqueous dissolvable microneedles (dMNs; 200 μm height) for efficient, precisely controlled, and convenient delivery of Au NPs into hamster oral tissue in vivo. The Au NPs were then further briefly dissipated by ultrasound (US). The results showed 33% and 20% increase in average optical scattering intensity (contrast level) in dysplastic and normal tissues, respectively, and pinpointed pathological ... (Read Full Article)
    

    Comment on Article Mentions:   Zhongping Chen   UC Irvine   Petra Wilder-Smith

11. Quantitative comparison of the OCT imaging depth at 1300 nm and 1600 nm

    Explore Article opticsinfobase.org (Aug 3 2010)

    One of the present challenges in optical coherence tomography (OCT) is the visualization of deeper structural morphology in biological tissues. Owing to a reduced scattering, a larger imaging depth can be achieved by using longer wavelengths. In this work, we analyze the OCT imaging depth at wavelengths around 1300 nm and 1600 nm by comparing the scattering coefficient and OCT imaging depth for a range of Intralipid concentrations at constant water content. We observe an enhanced OCT imaging depth for 1600 nm compared to 1300 nm for Intralipid concentrations larger than 4 vol.%. For higher Intralipid concentrations, the imaging depth ... (Read Full Article)
    

    Comment on Article Mentions:   VU University Amsterdam   Ton G. van Leeuwen

12. Signal attenuation and box-counting
fractal analysis of optical coherence
tomography images of arterial tissue

    Explore Article opticsinfobase.org (Aug 3 2010) Cardiology

    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 (WHHL-MI) ... (Read Full Article)
    

    Comment on Article Mentions:   Shoude Chang   Youxin Mao   Costel Flueraru

13. Depth resolved photothermal OCT detection of macrophages in tissue using nanorose

    Explore Article opticsinfobase.org (Aug 3 2010) Cardiology

    Application of photothermal Optical Coherence Tomography (OCT) to detect macrophages in ex vivo rabbit arteries which have engulfed nanoclusters of gold coated iron oxide (nanorose) is reported. Nanorose engulfed by macrophages associated with atherosclerotic lesions in rabbit arteries absorb incident laser (800nm) energy and cause optical pathlength (OP) variation which is measured using photothermal OCT. OP variation in polydimethyl siloxane tissue phantoms containing varying concentrations of nanorose match values predicted from nanoparticle and material properties. Measurement of OP variation in rabbit arteries in response to laser excitation provides an estimate of nanorose concentration in atherosclerotic lesions of 2.5x109 particles/ml. OP ... (Read Full Article)
    

    Comment on Article Mentions:   Thomas E. Milner   Marc D. Feldman   University of Texas at Austin

14. A dual-modality optical coherence tomography and fluorescence lifetime imaging microscopy system for simultaneous morphological and biochemical tissue characterization

    Explore Article opticsinfobase.org (Aug 3 2010)

    Most pathological conditions elicit changes in the tissue optical response that may be interrogated by one or more optical imaging modalities. Any single modality typically only furnishes an incomplete picture of the tissue optical response, hence an approach that integrates complementary optical imaging modalities is needed for a more comprehensive non-destructive and minimally-invasive tissue characterization. We have developed a dual-modality system, incorporating optical coherence tomography (OCT) and fluorescence lifetime imaging microscopy (FLIM), that is capable of simultaneously characterizing the 3-D tissue morphology and its biochemical composition. The Fourier domain OCT subsystem, at an 830 nm center wavelength, provided high-resolution morphological ... (Read Full Article)
    

    Comment on Article Mentions:   Texas A&M University   Brian E. Applegate   Joseph A. Izatt

15. Depth-resolved imaging and detection of micro-retroreflectors within biological tissue using Optical Coherence Tomography

    Explore Article opticsinfobase.org (Aug 2 2010)

    A new approach to in vivo biosensor design is introduced, based on the use of an implantable micron-sized retroreflector-based platform and non-invasive imaging of its surface reflectivity by Optical Coherence Tomography (OCT). The possibility of using OCT for the depth-resolved imaging and detection of micro-retroreflectors in highly turbid media, including tissue, is demonstrated. The maximum imaging depth for the detection of the micro-retroreflector-based platform within the surrounding media was found to be 0.91 mm for porcine tissue and 1.65 mm for whole milk. With further development, it may be possible to utilize OCT and micro-retroreflectors as a tool for continuous ... (Read Full Article)
    

    Comment on Article Mentions:   Kirill V. Larin   University of Houston   Saratov State University

16. Interlaced spectrally encoded confocal scanning laser ophthalmoscopy and spectral domain optical coherence tomography

    Explore Article opticsinfobase.org (Aug 2 2010) Microscopy , Ophthalmology

    Scanning laser ophthalmoscopy (SLO) and spectral domain optical coherence tomography (SDOCT) have become essential clinical diagnostic tools in ophthalmology by allowing for video-rate noninvasive en face and depth-resolved visualization of retinal structure. Current generation multimodal imaging systems that combine both SLO and OCT as a means of image tracking remain complex in their hardware implementations. Here, we combine a spectrally encoded confocal scanning laser ophthalmoscope (SECSLO) with an ophthalmic SDOCT system. This novel implementation of an interlaced SECSLO-SDOCT system allows for video-rate SLO fundus images to be acquired alternately with high-resolution SDOCT B-scans as a means of image aiming, guidance, ... (Read Full Article)
    

    Comment on Article Mentions:   Yuankai K. Tao   Sina Farsiu   Joseph A. Izatt

17. Endoscopically guided spectral-domain OCT with double-balloon catheters

    Explore Article opticsinfobase.org (Jul 30 2010) Gastroenterology , Oncology

    Fourier-domain optical coherence tomography (OCT) and balloon-based catheters have furthered the potential of OCT as a real-time surveillance tool for Barrett’s esophagus (BE). However, a balloon catheter, which expands the esophagus and centers the catheter, applies direct pressure on the esophagus. This may affect the tissue appearance and the ability to detect dysplasia in BE. To study this effect, we propose a double-balloon catheter to allow imaging with and without balloon-tissue contact. A system design based on a spectral-domain OCT platform is reported and validated by acquisition of high quality, volumetric images of swine esophagus in vivo. (Read Full Article)
    

    Comment on Article Mentions:   Hui Wang   Michael W. Jenkins   Andrew M. Rollins

18. Speckle reduction in optical coherence tomography by strain compounding

    Explore Article opticsinfobase.org (Jul 13 2010)

    We present a speckle reduction technique for optical coherence tomography based on strain compounding. Decorrelation is introduced between B-scans by altering the sample’s strain. A theoretical description of the technique, based on a transfer-function formalism, and experimental results on silicone phantoms are presented. Nearly complete decorrelation between successive B-scan speckle patterns was observed for a variation in strain of 0.045. Strain compounding by averaging nine B-scans, with 0.003 strain increments between them, resulted in a 1.5-fold reduction in speckle contrast ratio. (Read Full Article)
    

    Comment on Article Mentions:   Brendan F. Kennedy   Timothy R. Hillman   Massachusetts Institute of Technology

19. Fourier domain mode-locked swept source
at 1050 nm based on a tapered amplifier

    Explore Article opticsinfobase.org (Jul 12 2010) Tunable Sources

    While swept source optical coherence tomography (OCT) in the 1050 nm range is promising for retinal imaging, there are certain challenges. Conventional semiconductor gain media have limited output power, and the performance of high-speed Fourier domain mode-locked (FDML) lasers suffers from chromatic dispersion in standard optical fiber. We developed a novel light source with a tapered amplifier as gain medium, and investigated the FDML performance comparing two fiber delay lines with different dispersion properties. We introduced an additional gain element into the resonator, and thereby achieved stable FDML operation, exploiting the full bandwidth of the tapered amplifier despite high dispersion. ... (Read Full Article)
    

    Comment on Article Mentions:   Peter E. Andersen   Wolfgang Wieser   Thomas Klein

20. Multiple-depth en face optical coherence tomography using active recirculation loops

    Explore Article opticsinfobase.org (Jun 30 2010)

    We present a novel low-coherence interferometer configuration, equipped in each arm with an adjustable optical path length ring. By compensating for the losses in the rings using semiconductor optical amplifiers, interference of low-coherence light after traversing the two rings 18 times is obtained. This configuration is employed to demonstrate simultaneous en face optical coherence tomography imaging at five different depths in a Drosophila melanogaster fly. (Read Full Article)
    

    Comment on Article Mentions:   Adrian G. Podoleanu   Adrian Bradu   University of Kent

21. Crosstalk rejection in parallel optical coherence tomography using spatially incoherent illumination with partially coherent sources

    Explore Article opticsinfobase.org (Jun 30 2010)

    The continuing improvement of high-speed area-scan cameras has made possible the construction of parallel optical coherence tomography (OCT) systems that are competitive with the fastest demonstrated swept-source OCT systems. Unfortunately, when imaging through turbid media using a partially coherent source, parallel OCT suffers resolution loss from coherent multiple scattering, a phenomenon known as crosstalk. We demonstrate the use of a full-field OCT system employing multimode fiber in the illumination arm to reduce the spatial coherence of a partially coherent source. By reducing the spatial coherence area below the system’s lateral resolution, we create a spatial coherence gate that rejects these ... (Read Full Article)
    

    Comment on Article Mentions:   Joseph A. Izatt   Duke University

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

    Explore Article opticsinfobase.org (Jun 29 2010)

    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. (Read Full Article)
    

    Comment on Article Mentions:   FDA   Rice University

23. Robust segmentation of intraretinal layers in the normal human fovea using a novel statistical model based on texture and shape analysis

    Explore Article opticsinfobase.org (Jun 24 2010) Ophthalmology

    A novel statistical model based on texture and shape for fully automatic intraretinal layer segmentation of normal retinal tomograms obtained by a commercial 800nm optical coherence tomography (OCT) system is developed. While existing algorithms often fail dramatically due to strong speckle noise, non-optimal imaging conditions, shadows and other artefacts, the novel algorithm’s accuracy only slowly deteriorates when progressively increasing segmentation task difficulty. Evaluation against a large set of manual segmentations shows unprecedented robustness, even in the presence of additional strong speckle noise, with dynamic range tested down to 12dB, enabling segmentation of almost all intraretinal layers in cases previously inaccessible ... (Read Full Article)
    

    Comment on Article Mentions:   Wolfgang Drexler   Boris Hermann   Boris Povazay

24. In vivo 3D human vocal fold imaging with polarization sensitive optical coherence tomography and a MEMS scanning catheter

    Explore Article opticsinfobase.org (Jun 23 2010) Otolaryngology

    We present in-vivo 3D human vocal fold images with polarization sensitive optical coherence tomography (PS-OCT). Characterizing the extent and location of vocal fold lesions provides useful information in guiding surgeons during phonomicrosurgery. Previous studies showed that PS-OCT imaging can distinguish vocal fold lesions from normal tissue, but these studies were limited to 2D cross-sectional imaging and were susceptible to sampling error. In-vivo 3D endoscopic imaging was performed by using a recently developed 2-axis MEMS scanning catheter and a spectral domain OCT (SD-OCT), running at 18.5 frames/s. Imaging was performed in the operating room with patients under general anesthesia and 3D ... (Read Full Article)
    

    Comment on Article Mentions:   B. Hyle Park   Massachusetts General Hospital   Harvard University

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