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    1. In vivo automated quantification of quality of apples during storage using optical coherence tomography images

      In vivo automated quantification of quality of apples during storage using optical coherence tomography images

      Moisture content is an important feature of fruits and vegetables. As 80% of apple content is water, so decreasing the moisture content will degrade the quality of apples (Golden Delicious). The computational and texture features of the apples were extracted from optical coherence tomography (OCT) images. A support vector machine with a Gaussian kernel model was used to perform automated classification. To evaluate the quality of wax coated apples during storage in vivo , our proposed method opens up the possibility of fully automated quantitative analysis based on the morphological features of apples. Our results demonstrate that the analysis of the ...

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    2. Tunable optical coherence tomography in the infrared range using visible photons

      Tunable optical coherence tomography in the infrared range using visible photons

      Optical coherence tomography (OCT) is an appealing technique for bio-imaging, medicine, and material analysis. For many applications, OCT in mid- and far-infrared (IR) leads to significantly more accurate results. Reported mid-IR OCT systems require light sources and photodetectors which operate in mid-IR range. These devices are expensive and need cryogenic cooling. Here, we report a proof-of-concept demonstration of a wavelength tunable IR OCT technique with detection of only visible range photons. Our method is based on the nonlinear interference of frequency correlated photon pairs. The nonlinear crystal, introduced in the Michelson-type interferometer, generates photon pairs with one photon in the ...

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    3. Practical implementation of spectral-intensity dispersion-canceled optical coherence tomography with artifact suppression

      Practical implementation of spectral-intensity dispersion-canceled optical coherence tomography with artifact suppression

      Dispersion-canceled optical coherence tomography (OCT) based on spectral intensity interferometry was devised as a classical counterpart of quantum OCT to enhance the basic performance of conventional OCT. In this paper, we demonstrate experimentally that an alternative method of realizing this kind of OCT by means of two optical fiber couplers and a single spectrometer is a more practical and reliable option than the existing methods proposed previously. Furthermore, we develop a recipe for reducing multiple artifacts simultaneously on the basis of simple averaging and verify experimentally that it works successfully in the sense that all the artifacts are mitigated effectively ...

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    4. Identification of Age-Related Macular Degeneration Using OCT Images

      Identification of Age-Related Macular Degeneration Using OCT Images

      Age-related Macular Degeneration is the most leading retinal disease in the recent years. Macular degeneration occurs when the central portion of the retina, called macula deteriorates. As the deterioration occurs with the age, it is commonly referred as Age-related Macular Degeneration. This disease can be visualized by several imaging modalities such as Fundus imaging technique, Optical Coherence Tomography (OCT) technique and many other. Optical Coherence Tomography is the widely used technique for screening the Age-related Macular Degeneration disease, because it has an ability to detect the very minute changes in the retina. The Healthy and AMD affected OCT images are ...

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    5. TiO2 nanoparticles as exogenous contrast agent for 1 µm swept source optical coherence tomography: an in vitro study

      TiO2 nanoparticles as exogenous contrast agent for 1 µm swept source optical coherence tomography: an in vitro study

      Optical coherence tomography (OCT) is a rapidly evolving, robust technology that has profoundly changed the practice of medical imaging. Swept source OCT (SSOCT) combines the standard time domain and the spatially encoded frequency domain OCT. We have employed a high-speed SSOCT system that utilizes a swept source laser with an A-scan rate of 100 kHz and a central wavelength of 1060 nm for the imaging of the tissue. SSOCT at 1060 nm allows for high penetration in the tissue. TiO 2 nanoparticles (NPs) are mostly used for various experimental purposes as an exogenous imaging contrast agent. The in vitro imaging ...

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      Mentions: Raju Poddar
    6. Feasibility of speckle variance OCT for imaging cutaneous microvasculature regeneration during healing of wounds in diabetic mice

      Feasibility of speckle variance OCT for imaging cutaneous microvasculature regeneration during healing of wounds in diabetic mice

      We report on a study to assess the feasibility of a swept source-based speckle variance optical coherence tomography setup for monitoring cutaneous microvasculature. Punch wounds created in the ear pinnae of diabetic mice were monitored at different times post wounding to assess the structural and vascular changes. It was observed that the epithelium thickness increases post wounding and continues to be thick even after healing. Also, the wound size assessed by vascular images is larger than the physical wound size. The results show that the developed speckle variance optical coherence tomography system can be used to monitor vascular regeneration during ...

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    7. In vivo classification of human skin burns using machine learning and quantitative features captured by optical coherence tomography

      In vivo classification of human skin burns using machine learning and quantitative features captured by optical coherence tomography

      We report the first fully automated detection of human skin burn injuries in vivo , with the goal of automatic surgical margin assessment based on optical coherence tomography (OCT) images. Our proposed automated procedure entails building a machine-learning-based classifier by extracting quantitative features from normal and burn tissue images recorded by OCT. In this study, 56 samples (28 normal, 28 burned) were imaged by OCT and eight features were extracted. A linear model classifier was trained using 34 samples and 22 samples were used to test the model. Sensitivity of 91.6% and specificity of 90% were obtained. Our results demonstrate ...

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    8. Silver nanoparticles (AgNPs) as a contrast agent for imaging of animal tissue using swept-source optical coherence tomography (SSOCT)

      Silver nanoparticles (AgNPs) as a contrast agent for imaging of animal tissue using swept-source optical coherence tomography (SSOCT)

      We present noninvasive three-dimensional depth-resolved imaging of animal tissue with a swept-source optical coherence tomography system at 1064 nm center wavelength and silver nanoparticles (AgNPs) as a potential contrast agent. A swept-source laser light source is used to enable an imaging rate of 100 kHz (100 000 A-scans s −1 ). Swept-source optical coherence tomography is a new variant of the optical coherence tomography (OCT) technique, offering unique advantages in terms of sensitivity, reduction of motion artifacts, etc. To enhance the contrast of an OCT image, AgNPs are utilized as an exogeneous contrast agent. AgNPs are synthesized using a modified Tollens ...

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      Mentions: Raju Poddar
    9. Estimation and compensation of dispersion for high-resolution optical coherence tomography system

      Estimation and compensation of dispersion for high-resolution optical coherence tomography system

      Balanced reference-sample arm dispersion is critical in optical coherence tomography systems in order to attain images with the highest axial resolution. Here, an experimental method for the estimation and correction of dispersion in an optical coherence tomography system is presented. The system dispersion was computed from two optical coherence tomography images of the reference mirror that were symmetrically placed around the zero delay point. The method was tested using a broad bandwidth spectral domain optical coherence tomography system, compensating for the dispersion caused by a 3-mm-thick fused silica flat placed in the sample arm. Using our method, dispersion compensation was ...

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    10. Quantitative reconstructions in multi-modal photoacoustic and optical coherence tomography imaging

      Quantitative reconstructions in multi-modal photoacoustic and optical coherence tomography imaging

      In this paper we perform quantitative reconstruction of the electric susceptibility and the Grüneisen parameter of a non-magnetic linear dielectric medium using measurement of a multi-modal photoacoustic and optical coherence tomography system. We consider the mathematical model presented in Elbau et al (2015 Handbook of Mathematical Methods in Imaging ed O Scherzer (New York: Springer) pp 1169–204), where a Fredholm integral equation of the first kind for the Grüneisen parameter was derived. For the numerical solution of the integral equation we consider a Galerkin type method.

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    11. Diffusion tensor optical coherence tomography

      Diffusion tensor optical coherence tomography

      In situ measurements of diffusive particle transport provide insight into tissue architecture, drug delivery, and cellular function. Analogous to diffusion-tensor magnetic resonance imaging (DT-MRI), where the anisotropic diffusion of water molecules is mapped on the millimeter scale to elucidate the fibrous structure of tissue, here we propose diffusion-tensor optical coherence tomography (DT-OCT) for measuring directional diffusivity and flow of optically scattering particles within tissue. Because DT-OCT is sensitive to the sub-resolution motion of Brownian particles as they are constrained by tissue macromolecules, it has the potential to quantify nanoporous anisotropic tissue structure at micrometer resolution as relevant to extracellular matrices ...

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    12. Non-invasive spectroscopic techniques in the diagnosis of non-melanoma skin cancer

      Non-invasive spectroscopic techniques in the diagnosis of non-melanoma skin cancer

      The number of non-melanoma skin cancers is increasing worldwide and has become an important health and economic issue. Early detection and treatment of skin cancer can significantly improve patient outcome. Therefore there is an increase in the demand for proper management and effective non-invasive diagnostic modalities in order to avoid relapses or unnecessary treatments. Although the gold standard of diagnosis for non-melanoma skin cancers is biopsy followed by histopathology evaluation, optical non-invasive diagnostic tools have obtained increased attention. Emerging non-invasive or minimal invasive techniques with possible application in the diagnosis of non-melanoma skin cancers include high-definition optical coherence tomography, fluorescence ...

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    13. Refractive index tomography based on optical coherence tomography and tomographic reconstruction algorithm

      Refractive index tomography based on optical coherence tomography and tomographic reconstruction algorithm

      Refractive index (RI) tomography based on not quantitative phase imaging (QPI) but optical coherence tomography (OCT) is proposed. In conventional RI tomography, the phase unwrapping process deteriorates measurement accuracy owing to the unwrapping error. To eliminate the unwrapping process, the introduction of OCT is proposed, because OCT directly provides optical thickness. The proposed method can improve measurement accuracy owing to the removal of the phase unwrapping error. The feasibility of the method is confirmed by numerical simulations and optical experiments. These results show that the proposed method can reduce measurement errors even when an object shows phase changes much larger ...

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    14. Silicon nanoparticles as contrast agents in the methods of optical biomedical diagnostics

      Silicon nanoparticles as contrast agents in the methods of optical biomedical diagnostics

      The efficiency of light scattering by nanoparticles formed using the method of picosecond laser ablation of silicon in water and by nanoparticles of mechanically grinded mesoporous silicon is compared. The ensembles of particles of both types possess the scattering coefficients sufficient to use them as contrast agents in optical coherence tomography (OCT), particularly in the range of wavelengths 700–1000 nm, where the absorption of both silicon and most biological and mimicking tissues is small. According to the Mie theory the main contribution to the scattering in this case is made by the particles having a relatively large size (150 ...

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    15. Full resolution Fourier domain optical coherence tomography

      Full resolution Fourier domain optical coherence tomography

      The complex conjugate ambiguity in Fourier domain optical coherence tomography (FDOCT) is a major roadblock that prevents full-detector resolution for the depth scan in single shot operation for the individual A-scan. Current techniques to eliminate this problem involve changing the experimental set-up, usually complicating the OCT system. In this work we show that the standard FDOCT spectrum data when resampled appropriately can be cast exactly in terms of type-1 discrete cosine transform (DCT). Additionally, a sparse reconstruction method in the DCT domain enables image recovery with full-detector resolution, thus effectively doubling the depth scan resolution. In a realistic simulation study ...

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    16. Spiking cortical model based non-local means method for despeckling multiframe optical coherence tomography data

      Spiking cortical model based non-local means method for despeckling multiframe optical coherence tomography data

      Optical coherence tomography (OCT) images are severely degraded by speckle noise. Existing methods for despeckling multiframe OCT data cannot deliver sufficient speckle suppression while preserving image details well. To address this problem, the spiking cortical model (SCM) based non-local means (NLM) method has been proposed in this letter. In the proposed method, the considered frame and two neighboring frames are input into three SCMs to generate the temporal series of pulse outputs. The normalized moment of inertia (NMI) of the considered patches in the pulse outputs is extracted to represent the rotational and scaling invariant features of the corresponding patches ...

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    17. Speckle noise reduction for optical coherence tomography images via non-local weighted group low-rank representation

      Speckle noise reduction for optical coherence tomography images via non-local weighted group low-rank representation

      In this work, a non-local weighted group low-rank representation (WGLRR) model is proposed for speckle noise reduction in optical coherence tomography (OCT) images. It is based on the observation that the similarity between patches within the noise-free OCT image leads to a high correlation between them, which means that the data matrix grouped by these similar patches is low-rank. Thus, the low-rank representation (LRR) is used to recover the noise-free group data matrix. In order to maintain the fidelity of the recovered image, the corrupted probability of each pixel is integrated into the LRR model as a weight to regularize ...

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    18. Noninvasive monitoring of blood glucose concentration in diabetic patients with optical coherence tomography

      Noninvasive monitoring of blood glucose concentration in diabetic patients with optical coherence tomography

      Optical coherence tomography (OCT) has been used to noninvasively monitor the blood glucose concentration (BGC) in healthy subjects with good accuracy and acceptable specificity. Based on this, the paper further considered the possibility of OCT in noninvasive monitoring BGC in diabetic patients. The OCT signal slope (OCTSS) changed with variation of BGC. The correlation coefficient R between BGC and OCTSS in diabetic patients was 0.91; while the correlation coefficient R in healthy volunteers was 0.78. Thus, a better linear dependence of OCTSS on BGC in diabetic patients was presented in the experiment. The results showed that the capability ...

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    19. Full-range ultrahigh-resolution spectral-domain optical coherence tomography in 1.7 µm wavelength region for deep-penetration and high-resolution imaging of turbid tissues

      Full-range ultrahigh-resolution spectral-domain optical coherence tomography in 1.7 µm wavelength region for deep-penetration and high-resolution imaging of turbid tissues

      For the first time, we developed a full-range ultrahigh-resolution (UHR) spectral-domain optical coherence tomography (SD-OCT) technique working in the 1.7 µm wavelength region. This technique allowed high-resolution, deep-tissue imaging. By using a supercontinuum source operating at a wavelength of 1.7 µm, an axial resolution of 3.6 µm in a tissue specimen was achieved. To enhance the imaging depth of UHR-SD-OCT, we performed full-range OCT imaging based on a phase modulation method. We demonstrated the three-dimensional (3D) imaging of a mouse brain with the developed system, and specific structures in the mouse brain were clearly visualized at depths ...

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    20. Simple model to simulate OCT-depth signal in weakly and strongly scattering homogeneous media

      Simple model to simulate OCT-depth signal in weakly and strongly scattering homogeneous media

      We present a simple and efficient Monte Carlo model to predict the scattering coefficients and the influence of multiple photon scattering with increasing concentration of scattering centers from optical coherence tomography (OCT) data. While the model reliably estimates optical sample parameters for a broad range of concentrations, it does not require inclusion of more complex phenomena such as dependent scattering. Instead, it relies on a particular weighting function which is introduced to describe various orders of multiple scattering events. In weakly scattering homogeneous media the measured scattering coefficient depends linearly on the concentration of scattering centers. In the case of ...

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    21. Optical coherence tomography for visualizing transient strains and measuring large deformations in laser-induced tissue reshaping

      Optical coherence tomography for visualizing transient strains and measuring large deformations in laser-induced tissue reshaping

      In the context of the development of emerging laser-assisted thermo-mechanical technologies for non-destructive reshaping of avascular collagenous tissues (cartilages and cornea), we report the first application of phase-sensitive optical coherence tomography (OCT) for visualizing transient strains involving supra-wavelength inter-frame displacements of scatterers. Usually phase-sensitive OCT assumes the visualization of sub-pixel and even sub-wavelength displacements of scatterers and fairly small strains (say, <10 −3 ), which conventionally implies the necessity of averaging for enhancing the effective signal-to-noise ratio and, correspondingly, the application of small-amplitude actuators producing periodic deformations. The original approach used here allows for direct estimation of elevated strains ~10 −2 ...

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    22. Spectral phase-based automatic calibration scheme for swept source-based optical coherence tomography systems

      Spectral phase-based automatic calibration scheme for swept source-based optical coherence tomography systems

      The automatic calibration in Fourier-domain optical coherence tomography (FD-OCT) systems allows for high resolution imaging with precise depth ranging functionality in many complex imaging scenarios, such as microsurgery. However, the accuracy and speed of the existing automatic schemes are limited due to the functional approximations and iterative operations used in their procedures. In this paper, we present a new real-time automatic calibration scheme for swept source-based optical coherence tomography (SS-OCT) systems. The proposed automatic calibration can be performed during scanning operation and does not require an auxiliary interferometer for calibration signal generation and an additional channel for its acquisition. The ...

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    23. Depth-resolved 3D visualization of coronary microvasculature with optical microangiography

      Depth-resolved 3D visualization of coronary microvasculature with optical microangiography

      In this study, we propose a novel implementation of optical coherence tomography-based angiography combined with ex vivo perfusion of fixed hearts to visualize coronary microvascular structure and function. The extracorporeal perfusion of Intralipid solution allows depth-resolved angiographic imaging, control of perfusion pressure, and high-resolution optical microangiography. The imaging technique offers new opportunities for microcirculation research in the heart, which has been challenging due to motion artifacts and the lack of independent control of pressure and flow. With the ability to precisely quantify structural and functional features, this imaging platform has broad potential for the study of the pathophysiology of microvasculature ...

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    24. Wideband ultrafast fiber laser sources for OCT and metrology

      Wideband ultrafast fiber laser sources for OCT and metrology

      Fiber lasers, which use optical fibers as ideal waveguides, have been attracting a great deal of attention as stable, practical, and maintenance-free lasers. Using a combination of an ultrashort-pulse fiber laser and a nonlinear fiber, we can realize wideband highly functional ultrafast fiber laser sources. The generation of ultrashort pulses with wide wavelength tunability and supercontinua based on fiber lasers and nonlinear fibers has been demonstrated. These techniques are useful for laser applications, especially for imaging and metrology. In this topical review, the fundamentals of and recent progress in wideband ultrafast fiber laser sources and their applications are reviewed mainly ...

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    1-24 of 165 1 2 3 4 5 6 7 »
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