1. 1-24 of 651 1 2 3 4 ... 26 27 28 »
    1. Radiographic, microcomputer tomography, and optical coherence tomography investigations of ceramic interfaces

      Radiographic, microcomputer tomography, and optical coherence tomography investigations of ceramic interfaces

      Imagistic investigation of the metal-ceramic crowns and fixed partial prostheses represent a very important issue in nowadays dentistry. At this time, in dental office, it is difficult or even impossible to evaluate a metal ceramic crown or bridge before setting it in the oral cavity. The possibilities of ceramic fractures are due to small fracture lines or material defects inside the esthetic layers. Material and methods: In this study 25 metal ceramic crowns and fixed partial prostheses were investigated by radiographic method (Rx), micro computer tomography (MicroCT) and optical coherence tomography (OCT) working in Time Domain, at 1300 nm. The ...

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    2. Numerical analysis of gradient index lens based optical coherence tomography imaging probes

      Numerical analysis of gradient index lens based optical coherence tomography imaging probes

      We report the numerical analysis of gradient index (GRIN) lens-based optical coherence tomography imaging probes to derive optimal design parameters. Long and short working distance probes with a small focal spot are considered. In each model, the working distance and beam waist are characterized and compared for different values of length and refractive index of the probe components. We also explore the influence of the outer tubing and refractive index of the sample media. Numerical results show that the adjustment of the maximum beam diameter and focusing angle at the end of the GRIN lens surface is very important for ...

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    3. Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography

      Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography
      Polarization-sensitive optical coherence tomography (PS-OCT) is known to be advantageous because of its additional tissue-specific contrast of the anterior eye. So far, this advantage has been shown only qualitatively. We evaluate the improved visibility afforded by 3-D PS corneal and anterior eye segment OCT (PS-CAS-OCT) in visualizing the trabecular meshwork (TM) based on statistical evidences. A total of 31 normal subjects participated in this study. The anterior eye segments of both the eyes of the subjects are scanned using a custom-made PS-CAS-OCT and the standard-scattering OCT (S-OCT) and polarization-sensitive phase-retardation OCT (P-OCT) images are obtained. Three graders grade the visibility ...
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    4. Quantitative measurement of attenuation coefficients of bladder biopsies using optical coherence tomography for grading urothelial carcinoma of the bladder

      Quantitative measurement of attenuation coefficients of bladder biopsies using optical coherence tomography for grading urothelial carcinoma of the bladder
      Real-time grading of bladder urothelial carcinoma (UC) is clinically important, but the current standard for grading (histopathology) cannot provide this information. Based on optical coherence tomography (OCT)-measured optical attenuation (µt), the grade of bladder UC could potentially be assessed in real time. We evaluate ex vivo whether µt differs between different grades of UC and benign bladder tissue. Human bladder tissue specimens are examined ex vivo by 850-nm OCT using dynamic focusing. Three observers independently determine the µt from the OCT images, and three pathologists independently review the corresponding histology slides. For both methods, a consensus diagnosis is made ...
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    5. Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography

      Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography

      Hemodynamics is thought to play a major role in heart development, yet tools to quantitatively assess hemodynamics in the embryo are sorely lacking. The especially challenging analysis of hemodynamics in the early embryo requires new technology. Small changes in blood flow could indicate when anomalies are initiated even before structural changes can be detected. Furthermore, small changes in the early embryo that affect blood flow could lead to profound abnormalities at later stages. We present a demonstration of 4-D Doppler optical coherence tomography (OCT) imaging of structure and flow, and present several new hemodynamic measurements on embryonic avian hearts at ...

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    6. Spectral Doppler optical coherence tomography imaging of localized ischemic stroke in a mouse model

      Spectral Doppler optical coherence tomography imaging of localized ischemic stroke in a mouse model
      We report the use of spectral Doppler optical coherence tomography imaging (SDOCTI) for quantitative evaluation of dynamic blood circulation before and after a localized ischemic stroke in a mouse model. Rose Bengal photodynamic therapy (PDT) is used as a noninvasive means for inducing localized ischemia in cortical microvasculature of the mouse. Fast, repeated Doppler optical coherence tomography scans across vessels of interest are performed to record flow dynamic information with high temporal resolution. Doppler-angle-independent flow indices are used to quantify vascular conditions before and after the induced ischemia by the photocoagulation of PDT. The higher (or lower) flow resistive indices ...
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    7. Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography

      Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography
      We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the ...
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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. Linear polarization detection of polarization-sensitive optical coherence tomography in the early detection of the application of dental caries

      Linear polarization detection of polarization-sensitive optical coherence tomography in the early detection of the application of dental caries
      Polarization-Sensitive Optical Coherence Tomography (PS-OCT) is an important functional OCT. By extracting the polarization properties from PS-OCT signals we can obtain more information about the structural and optical features of tissues or materials. Dental caries is one of the most prevalent chronic diseases of people worldwide. The primary caries detection and the structure transformation of the enamel and dentin between sound and broken teeth are given serious attention by dentists. In this paper, using our Fourier-domain polarization-sensitive optical coherence tomography (FD-PS-OCT) setup by three incident linear polarization states and two detection states, we can get the 9 Mueller matrix elements ...
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    10. Monitoring changes of optical attenuation coefficients of acupuncture points during laser acupuncture by optical coherence tomography

      Monitoring changes of optical attenuation coefficients of acupuncture points during laser acupuncture by optical coherence tomography

      The physical properties of acupuncture point were important to discover the mechanism of acupuncture meridian. In this paper, we used an optical coherence tomography to monitor in vivo the changes of optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point during laser irradiation on Yangxi acupuncture point. The optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point were obtained by fitting the raw data according to the Beer-Lambert's law. The experimental results showed that the optical attenuation coefficient of Hegu acupuncture point decreased during the laser acupuncture, in contrast to a barely changed result in that of ...

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    11. Monitoring the process of tissue healing of rat skin in vivo after laser irradiation based on optical coherence tomography

      Monitoring the process of tissue healing of rat skin in vivo after laser irradiation based on optical coherence tomography
      It is imperative to evaluate the tissue wound healing response after laser irradiation so as to develop effective devices for this clinical indication, and evaluate the thermal damage degree to take appropriate treatment. In our research, we prepare 6 white rat (approximately 2 months old, weight :28±2g). Each rat was injected intraperitoneally a single dose of 2% pentobarbital sodium. After the rat was anesthetized, the two side of the rats' back were denuded and antisepsised a standardized. An Er:YAG laser (2940nm, 2.5J/cm2, single spot, 4 times) was irradiated on rat skin in vivo, and the skin ...
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    12. Signal and noise analysis of optical coherence tomography in highly scattering material at 1550nm

      Signal and noise analysis of optical coherence tomography in highly scattering material at 1550nm
      The signal and noise properties of standard time domain optical coherence tomography system are analyzed in near-infrared region based on extended Huygens-Fresnel principle. The signal-to-noise ratio and maximum probing depth are estimated for scattering media with discontinuity plane inside. In numerical simulation, the relationship between coherent signal and scattering coefficients, and depth dependence SNR are calculated. The difference between specular and diffuse reflection is given out and analyzed. Numerical result is verified by well established experiment with different concentration mixture solution of IntralipidTM, from 1% to 15%. The OCT system consists of fiber Michelson interferometer and 1550 nm ASE optical ...
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    13. Monitoring collagen remodeling on opto-thermal response of photoaged skin irradiated by Er:YAG laser with optical coherence tomography

      Monitoring collagen remodeling on opto-thermal response of photoaged skin irradiated by Er:YAG laser with optical coherence tomography

      The Optical Coherence Tomography technology was used to perform noninvasive cross-sectional imaging of internal structures in photoaged mouse skin irradiated by Er:YAG laser. The mice were irradiated chronically with a steady dose of ultraviolet irradiation. Various laser light doses were irradiated on the back skins of the photoaged mouse. An OCT was used to observe the process of the collagen remodeling in dermis. The relationship between optical characteristic parameter such as attenuation coefficient and light dose was discovered. The total attenuation coefficient increased when the light dose increased. Our findings showed that Er:YAG laser could be used for ...

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    14. Effects of the optical transfer function on velocity estimation with optical coherence tomography

      Effects of the optical transfer function on velocity estimation with optical coherence tomography

      Doppler optical coherence tomography (DOCT) is an extension of optical coherence tomography (OCT) for measuring blood flow dynamics simultaneously with the microscopic structures at high spatial and velocity resolution. In this paper, we analyze the effects of parameters of the DOCT system on the optical transfer function (OTF) which finally affects the accuracy of the velocity estimation. Experimental data are given to show the effects. The methods of overcoming the effects are also pointed out.

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    15. Evaluation of whole blood coagulation process by optical coherence tomography

      Evaluation of whole blood coagulation process by optical coherence tomography
      This study was to investigate the feasibility of using optical coherence tomography (OCT) to evaluate whole blood coagulation process. Attenuation coefficients and 1/e light penetration depth (D1/e) against time of human whole blood during in vitro clot formation under static were measured from the OCT profiles of reflectance vs depth. The results obtained clearly showed that the optical parameters are able to identify three stages during the in vitro blood clotting process. It is concluded that D1/e measured by OCT is a potential parameter to quantify and follow the liquid-gel transition of blood during clotting.
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    16. Laser radar: from early history to new trends

      Laser radar: from early history to new trends
      The first steps of laser radar are discussed with the examples from range finding and designation. The followed successes in field tests and further fast development provided their wide use. Coherent laser radar, developed almost simultaneously, tried the ideas from microwaves including chirp technology for pulse compression, and Doppler mode of operation. This latter found a unique implementation in a cruise missile. In many applications, environmental studies very strongly rely upon the lidars sensing the wind, temperature, constituents, optical parameters. Lidars are used in the atmosphere and in the sea water measurements. Imaging and mapping is an important role prescribed ...
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    17. Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography

      Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography
      Drosophila melanogaster (fruit fly) is a central organism in biology and is becoming increasingly important in the cardiovascular sciences. Prior work in optical imaging of the D. melanogaster heart has focused on static and dynamic structural anatomy. In the study, it is demonstrated that Doppler optical coherence tomography can quantify dynamic heart wall velocity and hemolymph flow in adult D. melanogaster. Since hemolymph is optically transparent, a novel exogenous contrast technique is demonstrated to increase the backscatter-based intracardiac Doppler flow signal. The results presented here open up new possibilities for functional cardiovascular phenotyping of normal and mutant D. melanogaster.
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    18. Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography

      Comparison of phase-shifting techniques for in vivo full-range, high-speed Fourier-domain optical coherence tomography
      Single spectrometer-based complex conjugate artifact removal methods are evaluated for in vivo imaging with complementary metal-oxide semiconductor line scan camera based high-speed Fourier-domain optical coherence tomography (FD–OCT) at 100,000 axial scans per second. Performance of three different phase-shifting methods with the same OCT engine is evaluated using modified data acquisition schemes, depending on the requirements of each phase-shifting technique. The suppression ratio of complex conjugate artifact images using a paperboard is assessed for all tested methods. Several other characteristics, including a list of additional hardware requirements (beyond standard FD-OCT components) and data acquisition schemes for each of the ...
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    19. Human graft cornea and laser incisions imaging with micrometer scale resolution full-field optical coherence tomography

      Human graft cornea and laser incisions imaging with micrometer scale resolution full-field optical coherence tomography
      Micrometer scale resolution full-field optical coherence tomography (FF-OCT) is developed for imaging human graft corneas. Three-dimensional (3-D) images with ultrahigh resolution (respectively, 1 and 1.5 µm in the axial and transverse directions), comparable to traditional histological sections, are obtained allowing the visualization of the cells and the precise structure of the different layers that compose the tissue. The sensitivity of our device enables imaging the entire thickness of the cornea, even in edematous corneas more than 800 µm thick. Furthermore, we provide tomographic 3-D images of laser incisions inside the tissue at various depths without slicing the studied corneas ...
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      Mentions: Gaël Latour
    20. Speckle texture analysis of optical coherence tomography images

      Speckle texture analysis of optical coherence tomography images

      Optical coherence tomography (OCT) is an imaging technique based on the low coherence interferometry, in which signals are obtained based on the coherent addition of the back reflected light from the sample. Applying computational methods and automated algorithms towards the classification of OCT images allows a further step towards enhancing the clinical applications of OCT. One attempt towards classification could be achieved by statistically analyzing the texture of the noisy granular patterns - speckles that make the OCT images. An attempt has been made to quantify the scattering effects based on the speckle texture patterns the scatterers produce. Statistical inference is ...

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    21. Phase-sensitive optical coherence tomography imaging of the tissue motion within the organ of Corti at a subnanometer scale: a preliminary study

      Phase-sensitive optical coherence tomography imaging of the tissue motion within the organ of Corti at a subnanometer scale: a preliminary study
      Hearing loss can mean severe impairment to the quality of life. However, the biomechanical mechanisms of how the hearing organ, i.e., the organ of Corti (OC), responds to sound are still elusive, largely because there is currently no means available to image the 3-D motion characteristics of the OC. We present a novel use of the phase-sensitive spectral domain optical coherence tomography (PSOCT) to characterize the motion of cellular compartments within the OC at a subnanometer scale. The PSOCT system operates at 1310 nm with a spatial resolution of ~16 µm and an imaging speed of 47,000 A-lines ...
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    22. Liquid lens enabled optical coherence microscope with Gabor fusion

      Liquid lens enabled optical coherence microscope with Gabor fusion
      A custom optical microscope with an integrated liquid lens to enable an extended depth imaging in biological tissue has been fabricated and shown to provide subcellular resolution using Gabor image fusion in an optical coherence tomography setup. In this paper, we report on the development and assessment path of this technology over the last few years. Specifically, we report on the optical design as well as the MTF prediction and experimental measurements of the new optical microscope head. The microscope head was integrated in a custom optical coherence microscopy setup that is presented. Images of an African frog tadpole, ex ...
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    23. Polarimetric analysis of the human cornea measured by polarization-sensitive optical coherence tomography

      Polarimetric analysis of the human cornea measured by polarization-sensitive optical coherence tomography
      Corneal polarimetry measurement has been the object of several papers. The results of techniques like polarization-sensitive optical coherence tomography (PS-OCT), scanning laser polarimetry, or polarization microscopy are contradictory. Some studies propose a biaxial-like birefringence pattern, while others postulate that birefringence grows at corneal periphery. Several theoretical approaches were proposed for the interpretation of these measurements, but they usually lack accuracy and an adequate consideration of the nonnormal incidence on the tissue. We analyze corneal polarization effects measured by PS-OCT. In vivo and in vitro PS-OCT images of the human cornea are acquired. PS-OCT measurements are apparently not in agreement with ...
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    24. Combined image-processing algorithms for improved optical coherence tomography of prostate nerves

      Combined image-processing algorithms for improved optical coherence tomography of prostate nerves
      Cavernous nerves course along the surface of the prostate gland and are responsible for erectile function. These nerves are at risk of injury during surgical removal of a cancerous prostate gland. In this work, a combination of segmentation, denoising, and edge detection algorithms are applied to time-domain optical coherence tomography (OCT) images of rat prostate to improve identification of cavernous nerves. First, OCT images of the prostate are segmented to differentiate the cavernous nerves from the prostate gland. Then, a locally adaptive denoising algorithm using a dual-tree complex wavelet transform is applied to reduce speckle noise. Finally, edge detection is ...
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    1-24 of 651 1 2 3 4 ... 26 27 28 »
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