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    1. Sparse Domain Gaussianization for Multi-variate Statistical Modeling of Retinal OCT Images

      Sparse Domain Gaussianization for Multi-variate Statistical Modeling of Retinal OCT Images

      In this paper, a multivariate statistical model that is suitable for describing Optical Coherence Tomography (OCT) images is introduced. The proposed model is comprised of a multivariate Gaussianization function in sparse domain. Such an approach has two advantages, i.e. 1) finding a function that can effectively transform the input – which is often not Gaussian – into normally distributed samples enables the reliable application of methods that assume Gaussianity, 2) although multivariate Gaussianization in spatial domain is a complicated task and rarely results in closed-form analytical model, by transferring data to sparse domain, our approach facilitates multivariate statistical modeling of OCT ...

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    2. Towards Indicating Human Skin State In Vivo Using Geometry-Dependent Spectroscopic Contrast Imaging

      Towards Indicating Human Skin State In Vivo Using Geometry-Dependent Spectroscopic Contrast Imaging

      Skin plays a significant role in human body function and its collagen states change during the human skin ageing process, which affects skin function. We previously reported on geometry-dependent spectroscopic contrast achieved by spectroscopic micro-optical coherence tomography ( S μ OCT), which discovered that transversely oriented and regularly arranged nano-cylinders selectively backscatter the long-wavelength lights and generate spectral centroid (SC) shifts towards the long wavelengths within a spectral window of 700 − 950 nm . Here we further proposed a novel method towards indicating the state of human skin in vivo using geometry-dependent spectroscopic contrast imaging. The proposed method can obtain spectroscopic contrast images ...

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    3. 3D Shape Modeling and Analysis of Retinal Microvasculature in OCT-Angiography Images

      3D Shape Modeling and Analysis of Retinal Microvasculature in OCT-Angiography Images

      3D optical coherence tomography angiography (OCT-A) is a novel and non-invasive imaging modality for analyzing retinal diseases. The studies of microvasculature in 2D en face projection images have been widely implemented, but comprehensive 3D analysis of OCT-A images with rich depth-resolved microvascular information is rarely considered. In this paper, we propose a robust, effective, and automatic 3D shape modeling framework to provide a high-quality 3D vessel representation and to preserve valuable 3D geometric and topological information for vessel analysis. Effective vessel enhancement and extraction steps by means of curvelet denoising and optimally oriented flux (OOF) filtering are first designed to ...

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    4. Dynamic compensation of path length difference in optical coherence tomography by an automatic temperature control system of optical fiber

      Dynamic compensation of path length difference in optical coherence tomography by an automatic temperature control system of optical fiber

      Optical fiber is widely used in optical coherence tomography (OCT) to propagate light precisely with low attenuation and low dispersion. However, the total optical path length within the optical fiber varies in accordance with changes of the temperature. This leads changes in the total optical travel path of the interfering signals and results in shifting of OCT image position to an unintended depth pixel value. In this paper, we presented the temperature-based automatic path length compensating method in OCT to limit the external temperature effect and control the image position in micro-scale without manual movement of optical components. By utilizing ...

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    5. Synchronous fingerprint acquisition system based on total internal reflection and optical coherence tomography

      Synchronous fingerprint acquisition system based on total internal reflection and optical coherence tomography

      he research of external fingerprint collected by total internal reflection (TIR) has been carried out for decades and research of internal fingerprint of optical coherence tomography (OCT) has just begun. The internal fingerprint can be hardly affected by the finger surface status, due to its strong anti-interference and anti-spoofing ability, which can serve as a powerful supplement to external fingerprint. However, matching fingerprints acquired by different ways can lead to a drop in fingerprint recognition accuracy owing to the differences in fingerprint quality, distortions and detection areas. Whether the internal fingerprint can be used to replace the external fingerprint for ...

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    6. Super-Resolution of Optical Coherence Tomography Images by Scale Mixture Models

      Super-Resolution of Optical Coherence Tomography Images by Scale Mixture Models

      In this paper, a new statistical model is proposed for the single image super-resolution of retinal Optical Coherence Tomography (OCT) images. OCT imaging relies on interfero-metry, which explains why OCT images suffer from a high level of noise. Moreover, data subsampling is carried out during the acquisition of OCT A-scans and B-scans. So, it is necessary to utilize effective super-resolution algorithms to reconstruct high-resolution clean OCT images. In this paper, a nonlocal sparse model-based Bayesian framework is proposed for OCT restoration. For this reason, by characterizing nonlocal patches with similar structures, known as a group, the sparse coefficients of each ...

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    7. RAG-FW: A hybrid convolutional framework for the automated extraction of retinal lesions and lesion-influenced grading of human retinal pathology

      RAG-FW: A hybrid convolutional framework for the automated extraction of retinal lesions and lesion-influenced grading of human retinal pathology

      The identification of retinal lesions plays a vital role in accurately classifying and grading retinopathy. Many researchers have presented studies on optical coherence tomography (OCT) based retinal image analysis over the past. However, to the best of our knowledge, there is no framework yet available that can extract retinal lesions from multi-vendor OCT scans and utilize them for the intuitive severity grading of the human retina. To cater this lack, we propose a deep retinal analysis and grading framework (RAG-FW). RAG-FW is a hybrid convolutional framework that extracts multiple retinal lesions from OCT scans and utilizes them for lesion-influenced grading ...

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    8. Fast Retinal Segmentation Based on the Wave Algorithm

      Fast Retinal Segmentation Based on the Wave Algorithm

      The retinal layer segmentation technique of optical coherence tomography (OCT) data is essential for the diagnosis of ophthalmic and systemic diseases. To achieve fast and accurate retinal layer segmentation, a new medical image segmentation method (wave algorithm) is proposed based on the mathematical model of the fluid potential energy equation in fluid mechanics. A change in the gray value in the image is converted into a change in the potential energy in the ideal fluid (wave), thereby transforming the image segmentation problem into a problem that solves the potential energy based on the fluid potential energy equation. In the process ...

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    9. Full range line-field optical coherence tomography for high-accuracy measurements of optical lens

      Full range line-field optical coherence tomography for high-accuracy measurements of optical lens

      A full range line-field Fourier domain optical coherence tomography system (LF-FDOCT) with an accuracy at nanoscale was proposed for high-accuracy measurements of optical lens surface profile. The line-field surface curve information of optical lens could be obtained in one measurement which does not need point-by-point scanning used in traditional one-dimensional FDOCT system. The measurement accuracy of surface profile curve could be improved from micrometer scale to nanoscale by applying spectral centre correction method (SCCM) to the complex spectral interferogram. The corrected five phase shifting (CFPS) method was employed to eliminate the complexconjugate artifacts and the polychromatic error. Numerical simulation and ...

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    10. Optical coherence tomography/angiography-guided tumor ablation with a continuous-wave laser diode

      Optical coherence tomography/angiography-guided tumor ablation with a continuous-wave laser diode

      Laser ablation can be an effective modality for treatment, but it is complicated to apply continuous-wave (CW) light sources for laser ablation because of the unpredictable photothermal damage. In this study, an integrated theranostic system combining a low-cost CW laser diode with optical coherence tomography (OCT)/angiography (OCTA) was utilized for the in vivo ablation of tumor tissues. To examine the effect of laser exposure on tissue scattering characteristics, the OCT backscattering intensities of non-ablated and ablated tissues were analyzed, and the effect on the skin microvasculature produced by laser ablation was quantitatively evaluated. Moreover, the integrated system and the ...

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    11. A Flexible Touch-based Fingerprint Acquisition Device and A Benchmark Database using Optical Coherence Tomography

      A Flexible Touch-based Fingerprint Acquisition Device and A Benchmark Database using Optical Coherence Tomography

      Optical Coherence Tomography (OCT) is a high resolution imaging technology probing the internal structure of multilayered tissues. Since it provides subsurface fingerprint information which is identical to the surface texture but unaffected by any surface defects, OCT-based fingerprints open up a new domain for establishing robust and high security automatic fingerprint identification systems (AFISs). However, the development of OCT-based fingerprint recognition is hindered by the lack of public OCT-based fingerprint database for algorithm analysis and testing. This paper, for the first time, established an OCT-based fingerprint database with thousands of fingers using our custom-built acquisition device.(The website of this ...

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    12. Compact and Mobile Full-Field Optical Coherence Tomography Sensor for Subsurface Fingerprint Imaging

      Compact and Mobile Full-Field Optical Coherence Tomography Sensor for Subsurface Fingerprint Imaging

      Conventional fingerprint sensors that are deployed in real-life applications lack the ability to peer inside a finger beyond the external surface. Subsurface information can provide complimentary biometric characteristics associated with the finger. The subsurface fingerprints can also be employed when the quality of the external/surface fingerprints is affected. One of the most promising technologies for imaging below the surface of an external fingerprint is full-field optical coherent tomography (FF-OCT). However, the FF-OCT can be expensive and cumbersome, despite its proven ability for biometric use. In this paper, we describe the design and implementation of a compact, mobile and cost-effective ...

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    13. Visualising ganglion cell layer based on image entropy optimisation for adaptive contrast enhancement

      Visualising ganglion cell layer based on image entropy optimisation for adaptive contrast enhancement

      Optical coherence tomography cannot easily be used for visual identification of the ganglion cell layer (GCL) for diagnosing retinal diseases owing to the extremely low image contrast between adjacent layers. To solve this problem, the authors used a limit-clipping optimisation method along with the image entropy to enhance the image contrast of targeted layers. As a result, the GCL was successfully extracted using an intelligent tracking system without impacting the segmentation of other retinal layers and image morphology. The segmentation results were evaluated through comparisons with manual segmentation results provided by clinical experts. The results of this study should help ...

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    14. Optical Biopsy of Melanoma and Basal Cell Carcinoma Progression by Noncontact Photoacoustic and Optical Coherence Tomography: In vivo Multi-parametric Characterizing Tumor Microenvironment

      Optical Biopsy of Melanoma and Basal Cell Carcinoma Progression by Noncontact Photoacoustic and Optical Coherence Tomography: In vivo Multi-parametric Characterizing Tumor Microenvironment

      Measuring the structural and functional status of tumor microenvironment for malignant melanoma (MM) and basal cell carcinoma (BCC) is of profound significance in understanding dermatological condition for biopsy. However, conventional optical imaging techniques are limited to visualize superficial skin features and parameter information is deficient to depict pathophysiology correlations of skin diseases. Here, we demonstrate a preclinical device, all-optically integrated photoacoustic and optical coherence tomography (AOPA/OCT), that, for the first time, can simultaneously provide label-free biomarkers of vascular patterns, temporal and spatial heterogeneity of blood flow, and tissue micro-structure changes during tumor growth with pathophysiological correlations in mice models ...

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    15. Catheter-Based Polarization Sensitive Optical Coherence Tomography Using Similar Mueller Matrix Method

      Catheter-Based Polarization Sensitive Optical Coherence Tomography Using Similar Mueller Matrix Method

      Objective : Research of catheter-based polarization sensitive optical coherence tomography (PS-OCT) is a challenging field. In this paper, we present a new polarization determination method, similar Mueller matrix (SMM) method, for a catheter-based PS-OCT system using a standard clinical catheter probe with an outer diameter of 0.9 mm. Methods : The SMM method can remove the diattenuation and depolarization compositions by polar decomposition. By constructing the similarity between the measured Mueller matrices and sample matrices, the phase retardance of the sample can be determined from the trace of the measured matrices. Results : In the experiments, we find that images processed by ...

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    16. Machine-Learning Classification of Port Wine Stain With Quantitative Features of Optical Coherence Tomography Image

      Machine-Learning Classification of Port Wine Stain With Quantitative Features of Optical Coherence Tomography Image

      Port wine stain (PWS) is the benign congenital capillary malformation of skin, occurring in 0.3% to 0.5% of the population. In this paper, we build two automated support vector machine (SVM) based classifiers by extracting quantitative features from normal and PWS tissue images recorded by optical coherence tomography (OCT). We use both full feature set and simplified feature set for training. Accuracy of 92.7%, sensitivity of 92.3% and specificity of 93.8% were obtained for classifier with full feature set. Accuracy of 92.7%, sensitivity of 94.9% and specificity of 87.5% were obtained for ...

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    17. Optical Coherence Tomography Guided Robotic Needle Insertion for Deep Anterior Lamellar Keratoplasty

      Optical Coherence Tomography Guided Robotic Needle Insertion for Deep Anterior Lamellar Keratoplasty

      Objective: Deep anterior lamellar keratoplasty (DALK) significantly reduces the post-transplantation morbidity in patients eligible for partial-thickness cornea grafts. The popular "big bubble" technique for DALK is so challenging, however, that a significant fraction of corneal pneumodissection attempts fail for surgeons without extensive DALK-specific experience, even with previous-generation cross-sectional optical coherence tomography (OCT) guidance. We seek to develop robotic, volumetric OCT-guided technology capable of facilitating or automating the difficult needle insertion step in DALK. Methods: Our system provides for real-time volumetric corneal imaging, segmentation, and tracking of the needle insertion to display feedback for surgeons and to generate needle insertion plans ...

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    18. Simultaneous morphological and flow imaging enabled by megahertz intravascular Doppler optical coherence tomography

      Simultaneous morphological and flow imaging enabled by megahertz intravascular Doppler optical coherence tomography

      We demonstrate three-dimensional intravascular flow imaging compatible with routine clinical image acquisition workflow by means of megahertz (MHz) intravascular Doppler Optical Coherence Tomography (OCT). The OCT system relies on a 1.1 mm diameter motorized imaging catheter and a 1.5 MHz Fourier Domain Mode Locked (FDML) laser. Using a post processing method to compensate the drift of the FDML laser output, we can resolve the Doppler phase shift between two adjoining OCT A-line datasets. By interpretation of the velocity field as measured around the zero phase shift, the flow direction at specific angles can be qualitatively estimated. Imaging experiments ...

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    19. Segmentation Guided Registration for 3D Spectral-Domain Optical Coherence Tomography Images

      Segmentation Guided Registration for 3D Spectral-Domain Optical Coherence Tomography Images

      Medical image registration can be used for combining information from multiple imaging modalities, monitoring changes in size, shape or image intensity over time intervals. However, the development of such technique can be challenging for 3D spectral-domain optical coherence tomography (SD-OCT) imaging, because SD-OCT image is inherently noisy and its high resolution leads to high complexity of non-rigid registration. In this paper, a new segmentation guided approach is reported for registration of retinal OCT data. The proposed method models the 3D registration as a two-stage registration including x-y direction registration and z direction registration. In x-y direction registration, the vessel maps ...

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    20. Packaged Negative Axicon Optical Fiber Probe and Bessel Beam Interferometry for Refractive Index Measurement of Hazardous Liquid Sample

      Packaged Negative Axicon Optical Fiber Probe and Bessel Beam Interferometry for Refractive Index Measurement of Hazardous Liquid Sample

      In this work, we demonstrate the packaging of an optical fiber negative axicon probe generating Bessel beam and its application in the measurement of refractive index (RI) of hazardous liquids. The negative axicon probe is placed inside cascaded capillary tube capped with a glass coverslip of RI ~1.52 and thickness ~0.15 mm. The packaged probe, connected to a broadband source through an optical circulator, is dipped in different hazardous liquid samples. The reflected light from the air-glass as well as the glass-liquid interface couples to the negative axicon probe and interferes with the reference beam generated at the ...

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    21. Multi-level Dual-attention Based CNN for Macular Optical Coherence Tomography Classification

      Multi-level Dual-attention Based CNN for Macular Optical Coherence Tomography Classification

      In this letter, we propose a multi-level dual-attention model to classify two common macular diseases, age-related macular degeneration (AMD) and diabetic macular edema (DME) from normal macular eye conditions using optical coherence tomography (OCT) imaging technique. Our approach unifies the dual-attention mechanism at multi-levels of the pre-trained deep convolutional neural network (CNN). It provides a focused learning mechanism by taking into account both multi-level features based attention focusing on the salient coarser features and self-attention mechanism attending higher entropy regions of the finer features. Our proposed method enables the network to automatically focus on the relevant parts of the input ...

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    22. Intraoperative Speckle Variance Optical Coherence Tomography for Tissue Temperature Monitoring During Cutaneous Laser Therapy

      Intraoperative Speckle Variance Optical Coherence Tomography for Tissue Temperature Monitoring During Cutaneous Laser Therapy

      Background: Tissue temperature monitoring during cutaneous laser therapy can lead to safer and more effective treatments. In this study, we investigate the use of speckle variance optical coherence tomography (svOCT) to monitor real-time temperature changes in the excised human skin tissue sample during laser irradiation. Methods: To accomplish this, we combined the pulse laser system with a reference-based svOCT system. To calibrate the svOCT, the ex-vivo human skin samples from three individuals with tissues collected from the arm, face, and back were heated with 1-degree increments. Additionally, linear regression was used to extract and evaluate the linear relationship between the ...

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    23. Highlighting Directional Reflectance Properties of Retinal Substructures From D-OCT Images

      Highlighting Directional Reflectance Properties of Retinal Substructures From D-OCT Images

      Optical coherence tomography (OCT), which is routinely used in ophthalmology, enables transverse optical imaging of the retina and, hence, the identification of the different neuronal layers. Directional OCT (D-OCT) extends this technology by acquiring sets of images at different incidence angles of the light beam. In this way, reflectance properties of photoreceptor substructures are highlighted, enabling physicians to study their orientation, which is potentially an interesting biomarker for retinal diseases. Nevertheless, commercial OCT devices equipped to automate D-OCT acquisition do not yet exist, meaning that physicians manually deviate the light beam to acquire a set of D-OCT images sequentially. Therefore ...

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    24. A Step-Index Silicate Nonlinear Fiber With All Normal Flattened Dispersion for Coherent Supercontinuum

      A Step-Index Silicate Nonlinear Fiber With All Normal Flattened Dispersion for Coherent Supercontinuum

      A step-index silicate fiber with all normal flat dispersion was fabricated. Coherent supercontinuum (SC) spectrum spanning 1200 to 2000 nm was generated in a 5 cm silicate fiber pumped at 1560 nm. The numerical simulation result agreed with the experiment result. Also, highly coherent SC spectrum spanning from 1100 to 2100 nm with flatness <7 dB generated in the fiber with 57 kW pumping power according to simulation. The step-index silicate fiber is not only easy to prepare but also a promising candidate to achieve all-fiber structure for coherent SC.

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