1. 121-143 of 143 « 1 2 3 4 5 6
    1. Endoscopic spectral domain optical coherence tomography of murine colonic morphology to determine effectiveness of chemopreventive and chemotherapeutic agents in colorectal cancer

      Endoscopic spectral domain optical coherence tomography of murine colonic morphology to determine effectiveness of chemopreventive and chemotherapeutic agents in colorectal cancer

      Optical coherence tomography (OCT) is a minimally-invasive imaging modality capable of tracking the development of individual colonic adenomas. As such, OCT can be used to evaluate the mechanisms and effectiveness of chemopreventive and chemotherapeutic agents in colorectal cancer models. The data presented here represent part of a larger study evaluating α-difluoromethylornithine (DFMO) and Sulindac as chemopreventive and chemotherapeutic agents using mice treated with the carcinogen azoxymethane (AOM). 27 A/J mice were included in the chemoprevention study, subdivided into four treatment groups (No Drug, DFMO, Sulindac, DFMO/Sulindac). 30 mm lateral images of each colon at eight different rotations were ...

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    2. A miniature forward-imaging optical coherence tomography (OCT) probe

      A miniature forward-imaging optical coherence tomography (OCT) probe

      Optical coherence tomography (OCT) has had a tremendous global health impact upon the current ability to diagnose, treat, and monitor multiple eye diseases. We propose that a miniature forward-imaging OCT probe can be developed for real-time ocular imaging. A miniature 25-gauge forward-imaging probe was designed and developed to use with an 850 nm spectral-domain optical coherence tomography (SDOCT) system (Bioptigen, Inc. Durham, NC). Imaging parameters were determined. Ocular tissues were examined with the miniature OCT probe. A miniature SDOCT probe was developed with the scanning driver within the hand piece. The SDOCT fiber-scanning probe maximally transmitted power of 800 μW ...

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    3. Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors

      Adaptive optics optical coherence tomography for measuring phase and reflectance dynamics of photoreceptors

      Optical coherence tomography with adaptive optics (AO-OCT) is a noninvasive method for imaging the living retina at the microscopic level. We used AO-OCT technology to follow changes in cone photoreceptor outer segment (OS) length and reflectance. To substantially increase sensitivity of the length measurements, a novel phase retrieval technique was demonstrated, capable of detecting changes on a nanometer scale. We acquired volume videos of 0.65°x0.65° retinal patches at 1.5° temporal to the fovea over 75 and 105 minutes in two subjects. Volumes were dewarped and registered, after which the cone intensity, OS length, and referenced phase ...

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    4. Differential intensity contrast swept source optical coherence tomography for human retinal vasculature visualization

      Differential intensity contrast swept source optical coherence tomography for human retinal vasculature visualization

      We demonstrate an intensity-based motion sensitive method, called differential logarithmic intensity variance (DLOGIV), for 3D microvasculature imaging and foveal avascular zone (FAZ) visualization in the in vivo human retina using swept source optical coherence tomography (SS-OCT) at 1060 nm. A motion sensitive SS-OCT system was developed operating at 50,000 A-lines/s with 5.9 μm axial resolution, and used to collect 3D images over 4 mm2 in a normal subject eye. Multiple B-scans were acquired at each individual slice through the retina and the variance of differences of logarithmic intensities as well as the differential phase variances (DPV) was ...

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    5. The effects of different gold standards on the accuracy of optical coherence tomography

      The effects of different gold standards on the accuracy of optical coherence tomography

      Fourier domain optical coherence tomography (FD-OCT) can acquire cross-sectional images of scattering media. Reconstruction of FD-OCT images requires taking the Fourier Transform of the raw data; the accuracy of which depends on the processing algorithms used, among other things. To use the Fast Fourier Transform, data must be evenly sampled in wavenumber, which they generally are not. Thus, researchers must apply hardware- or softwarebased methods to resample the data accordingly. To the best of our knowledge there has been no study that compares different choices for gold standard datasets (i.e., different choices for assigning the sampled wavelengths); furthermore there ...

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    6. MEMS tunable VCSEL light source for ultrahigh speed 60kHz - 1MHz axial scan rate and long range centimeter class OCT imaging

      MEMS tunable VCSEL light source for ultrahigh speed 60kHz - 1MHz axial scan rate and long range centimeter class OCT imaging

      This paper demonstrates new wavelength swept light source technology, MEMS tunable VCSELs, for OCT imaging. The VCSEL achieves a combination of ultrahigh sweep speeds, wide spectral tuning range, flexibility in sweep trajectory, and extremely long coherence length, which cannot be simultaneously achieved with other technologies. A second generation prototype VCSEL is optically pumped at 980nm and a low mass electrostatically tunable mirror enables high speed wavelength tuning centered at ~1310nm with ~110nm of tunable bandwidth. Record coherence length >100mm enables extremely long imaging range. By changing the drive waveform, a single 1310nm VCSEL was driven to sweep at speeds from ...

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    7. Automated detection of chorio-scleral interface using polarization-sensitive optical coherence tomography

      Automated detection of chorio-scleral interface using polarization-sensitive optical coherence tomography

      A polarization sensitive optical coherence tomography based automated algorithm for segmentation of the chorio-scleral interface is presented. The algorithm employs a two-step segmentation approach. At first, local birefringence based segmentation with low precision is performed to roughly distinguish the choroid and sclera. Successively, a depth oriented slope fitting to phase retardation is applied in both the choroid and sclera. The interface is determined as the cross-point of the two phase retardation slope lines. The algorithm shows potential for functional, objective, and volumetric choroid thickness measurement

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    8. Dual-beam optical coherence tomography system for quantification of flow velocity in capillary phantoms

      Dual-beam optical coherence tomography system for quantification of flow velocity in capillary phantoms

      The quantification of (blood) flow velocity within the vasculature has potent diagnostic and prognostic potential. Assessment of flow irregularities in the form of increased permeability (micro haemorrhaging), the presence of avascular areas, or conversely the presence of vessels with enlarged or increased tortuosity in the acral regions of the body may provide a means of non-invasive in vivo assessment. If assessment of dermal flow dynamics were performed in a routine manner, the existence and prevalence of ailments such as diabetes mellitus, psoriatic arthritis and Raynaud's condition may be confirmed prior to clinical suspicion. This may prove advantageous in cases ...

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    9. Graphics processing unit based ultrahigh speed real-time multidimensional Fourier domain optical coherence tomography

      Graphics processing unit based ultrahigh speed real-time multidimensional Fourier domain optical coherence tomography

      In this paper, we systematically presented a series of graphics processing unit (GPU) based data processing methods for ultrahigh speed, real-time Fourier Domain optical coherence tomography (FD-OCT): GPU based algorithms including high-speed linear/cubic interpolation, non-uniform fast Fourier transform (NUFFT), numerical dispersion compensation, and multi-GPU implementation were developed to improve the image quality and stability of the system. Full-range complex-conjugate-free FD-OCT was also implemented on the GPU architecture to double the imaging range and to improve SNR. The maximum processing speed of >3.0 Giga-Voxel/second (>6.0 Mega-A-scan/ second of 1024-pixel FD-OCT) was achieved using NVIDIA's latest GPU ...

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    10. Wavelength multiplexing for FD-OCT speckle averaging

      Wavelength multiplexing for FD-OCT speckle averaging

      Quantitative analysis of OCT data can be strongly hampered by speckle. We propose a new method to reduce speckle, operating on a single Fourier-domain optical coherence tomography (FD-OCT) A-line. The full acquired spectrum is used for image generation, exhibiting fully developed speckle. By subdividing the same acquired spectrum in a number of distinct narrower windows, each with a different center frequency, several independent speckles can be generated. These can be averaged to yield a lower-resolution image with strongly reduced speckle. The full resolution image remains available for human interpretation; the low resolution version can be used for parametric imaging. We ...

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    11. Optical coherence tomography based angle-resolved backscattering studies on bovine tendon and cartilage

      Optical coherence tomography based angle-resolved backscattering studies on bovine tendon and cartilage

      The difference in the genetic make up of the constituent molecules in collagen fibers in tendon and articular cartilage is what makes them mechanically and functionally different. A comparative study carried out on the differences in the angle-resolved back-scattering properties obtained from optical coherence tomography based studies on the two different types of scatterers: collagen I and collagen II fibers in bovine tendon and bovine articular cartilage sample, respectively, is reported here. Tendon sample shows greater anisotropy in the angle-resolved scattering profile compared to that obtained from articular cartilage sample. Rayleigh-Gans scattering approximation is used to provide the qualitative support ...

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    12. Polarization-sensitive optical coherence tomography measurements with different phase modulation amplitude when using continuous polarization modulation

      Polarization-sensitive optical coherence tomography measurements with different phase modulation amplitude when using continuous polarization modulation

      We demonstrate theoretically and experimentally that the phase retardance and relative optic-axis orientation of a sample can be calculated without prior knowledge of the actual value of the phase modulation amplitude when using a polarization-sensitive optical coherence tomography system based on continuous polarization modulation (CPM-PS-OCT). We also demonstrate that the sample Jones matrix can be calculated at any values of the phase modulation amplitude in a reasonable range depending on the system effective signal-to-noise ratio. This has fundamental importance for the development of clinical systems by simplifying the polarization modulator drive instrumentation and eliminating its calibration procedure. This was validated ...

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    13. New developments in eye models with retina tissue phantoms for ophthalmic optical coherence tomography

      New developments in eye models with retina tissue phantoms for ophthalmic optical coherence tomography

      We document our latest work in developing eye models with solid-state retinal tissue phantoms designed for demonstrating, validating and comparing ophthalmic Optical Coherence Tomography (OCT) instruments. Eye models with retina tissue phantoms can serve a variety of purposes, including demonstrating OCT functionality and performance in both the clinic and exhibit hall, validating retina layer thickness measurements from different commercial OCT instruments and as an aide for the R&D engineer and field service technician in the development and repair of instruments, respectively. The ideal eye model for OCT, the optical cross-sectional imaging modality, would have a volumetric morphology and scattering ...

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      Mentions: UC Davis
    14. Ultrahigh resolution optical coherence tomography imaging of diseased rat lung using Gaussian shaped super continuum sources

      Ultrahigh resolution optical coherence tomography imaging of diseased rat lung using Gaussian shaped super continuum sources

      We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) imaging of lung tissues using fiber super continuum sources. The high power, low-noise, Gaussian shaped supercontinuum generated with ultrashort pulses and optical fibers at several wavelengths were used as the broadband light sources for UHR-OCT. For the 800 nm wavelength region, the axial resolution was 3.0 um in air and 2.0 um in tissue. Since the lung consists of tiny alveoli which are separated by thin wall, the UHR-OCT is supposed to be effective for lung imaging. The clear images of alveoli of rat were observed with and ...

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    15. Morphological image analysis for classification of gastrointestinal tissues using optical coherence tomography

      Morphological image analysis for classification of gastrointestinal tissues using optical coherence tomography

      Computer-aided diagnosis of ophthalmic diseases using optical coherence tomography (OCT) relies on the extraction of thickness and size measures from the OCT images, but such defined layers are usually not observed in emerging OCT applications aimed at "optical biopsy" such as pulmonology or gastroenterology. Mathematical methods such as Principal Component Analysis (PCA) or textural analyses including both spatial textural analysis derived from the two-dimensional discrete Fourier transform (DFT) and statistical texture analysis obtained independently from center-symmetric auto-correlation (CSAC) and spatial grey-level dependency matrices (SGLDM), as well as, quantitative measurements of the attenuation coefficient have been previously proposed to overcome this ...

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    16. Quantitative comparison of wavelength dependence on penetration depth and imaging contrast for ultrahigh-resolution optical coherence tomography using supercontinuum sources at five wavelength regions

      Quantitative comparison of wavelength dependence on penetration depth and imaging contrast for ultrahigh-resolution optical coherence tomography using supercontinuum sources at five wavelength regions

      Optical coherence tomography (OCT) is a non invasive optical imaging technology for micron-scale cross-sectional imaging of biological tissue and materials. We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) using fiber based supercontinuum sources. Although ultrahigh longitudinal resolution was achieved in several center wavelength regions, its low penetration depth is a serious limitation for other applications. To realize ultrahigh resolution and deep penetration depth simultaneously, it is necessary to choose the proper wavelength to maximize the light penetration and enhance the image contrast at deeper depths. Recently, we have demonstrated the wavelength dependence of penetration depth and imaging contrast ...

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    17. Lateral resolution improvement in oversampled Optical Coherence Tomography images assuming weighted oversampled multi-scatterer contributions

      Lateral resolution improvement in oversampled Optical Coherence Tomography images assuming weighted oversampled multi-scatterer contributions

      A novel method for lateral resolution improvement of Optical Coherence Tomography (OCT) images, which is independent of the focusing of the delivery optics and the depth of field, is presented. This method was inspired by radar range oversampling techniques. It is based on the lateral oversampling of the image and the estimation of the locations of the multiple scatterers which contribute to the signal. The information in the oversampled images is used to estimate the locations of multiple scatterers assuming each contributes a weighted portion to the detected signal, the weight determined by the location of the scatterer and the ...

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    18. Single-shot full complex spectrum spectrometer-based OCT with a single-line photodiode array

      Single-shot full complex spectrum spectrometer-based OCT with a single-line photodiode array

      An efficient technique of simultaneous obtaining of quadrature spectral components of interference signal in spectrometer-based OCT using a single-line linear photodiode array is proposed. The components are obtained in air-spaced non-polarization interferometer by partition of reference beam onto two parts and using an achromatic phase shifter. Several setups are described and compared.

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    19. Digital refocusing in optical coherence tomography

      Digital refocusing in optical coherence tomography

      The problem of restoration Optical Coherence Tomography (OCT) images, acquired with tightly focused probing beam, in out-of-focus region for improving lateral resolution of the OCT has been considered. Phase stability issue has been discussed and phase equalization algorithm has been proposed. After phase equalization, the algorithm of digital refocusing, based on some methods from the DH, have been applied to the simulated as well as to experimental OCT data, acquired with tightly focused scanning beam to restore micrometer lateral resolution in the whole investigated volume.

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    20. Complex conjugate term manipulation in optical frequency-domain imaging using the time-frequency distribution

      Complex conjugate term manipulation in optical frequency-domain imaging using the time-frequency distribution

      We discuss two methods which use the intrinsic dispersion imbalance between interferometer arms in order to address and manipulate the complex conjugate terms in spectral domain optical coherence tomography. Using projections of the time-frequency plane, we can manipulate small induced dispersion and obtain similar modification of the complex conjugate term as large amount of chromatic dispersion. The algorithm described spreads the energy of the complex conjugate term over the entire A-scan. The method is applied to simulated OCT depth signals and offered a mirror term suppression of 20 dB. The second method shows how we can use the time-frequency distribution ...

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    21. Spectral dependence of ultra-low dark count superconducting single photon detector for the evaluation of broadband parametric fluorescence

      Spectral dependence of ultra-low dark count superconducting single photon detector for the evaluation of broadband parametric fluorescence
      Superconducting nanowire single photon detectors (SNSPD) have unique characteristics of ultra low dark counts and wide spectrum sensitivity. These natures are indispensable for the evaluation of ultra-broadband parametric fluorescence, which are used for the quantum optical coherence tomography and novel optical non-linear experiments. Here we report the spectral dependence of the detection efficiency of a meander type SNSPD device, having reduced strip width of 50 nm, over a wide spectrum range up to near infra-red wavelength. The fiber coupled, meander type device was fabricated using 6 nm thick Niobium nitride (NbN) nanowires of reduced strip width, 50 nm, patterned over ...
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      Mentions: Osaka University
    22. Generation of broadband spontaneous parametric fluorescence and its application to quantum optical coherence tomography

      Generation of broadband spontaneous parametric fluorescence and its application to quantum optical coherence tomography
      Optical coherence tomography (OCT) based on Michelson interferometer has widely been utilized in biology and medicine as a type of optical biopsy and quantum optical coherence tomography (QOCT) based on Hong-Ou-Mandel interferometer has recently been demonstrated. By use of quantum entangled photon pairs generated via spontaneous parametric down conversion (SPDC) process, axial resolution of QOCT can be better than that of OCT in principle for a source of same bandwidth and group velocity dispersion (GVD) effect for QOCT can be automatically cancelled thanks to the frequency correlation of entangled photon pairs. To realize high-resolution QOCT, we need a broadband quantum ...
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    23. Quantification of Vascular Networks with the Aid of OCT in Order to Evaluate Re-Endothelialization after Peripheral Angioplasty

      Quantification of Vascular Networks with the Aid of OCT in Order to Evaluate Re-Endothelialization after Peripheral Angioplasty

      Purpose: In vivo dynamic visualization, recognition and quantification of vascular networks represent a very interesting methodological requirement of peripheral angioplasty. Optical coherence tomography (OCT) is a catheter‐based imaging method that employs near‐infrared light to produce high‐resolution intravascular images. The purpose of the present study is the inner‐outer lumen contours extraction as well as strut detection, so as to evaluate the re‐endothelialization degree in stented arteries derived from OCT images. Methods: Inner and outer lumen contours represent the regions of interest on OCT cross‐sectional images, from which data clinicians can determine degree of restenosis. In ...

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    121-143 of 143 « 1 2 3 4 5 6
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