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    1. Imaging depth adaptive resolution enhancement for optical coherence tomography via deep neural network with external attention

      Imaging depth adaptive resolution enhancement for optical coherence tomography via deep neural network with external attention

      Optical Coherence Tomography (OCT) is a promising non-invasive imaging technique that owns many biomedical applications. In this paper, a deep neural network is proposed for enhancing the spatial resolution of OCT en face images. Different from the previous reports, the proposed can recover high resolution en face images from low resolution en face images at arbitrary imaging depth. This kind of imaging depth adaptive resolution enhancement is achieved through an external attention mechanism, which takes advantage of morphological similarity between the arbitrary-depth and full-depth en face images. Firstly, the deep feature maps are extracted by a feature extraction network from ...

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    2. Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

      Phase-sensitive optical coherence tomography for non-contact monitoring photocuring process

      A method combining phase-contrast technique and spectral-domain optical coherence tomography (OCT) has been recently proposed for visualizing curing behaviors inside polymers (2020 Appl. Phys. Lett. 116 054103). Here, based on the method, a non-contact and highly-sensitive optical sensor is further developed to monitor the photocuring process of light-cured polymers. Compared with the existing method, the proposed optical sensor features two distinct advantages: (a) the sensor uses a point-detection OCT, rather than a line-field OCT, to capture the interference signal, which significantly improves its practicability and the measuring speed; (b) the sensor can simultaneously monitor the shrinkage strains and refractive index ...

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    3. Advanced imaging of dentin microstructure

      Advanced imaging of dentin microstructure

      This study aimed to demonstrate the feasibility of using optical coherence tomography (OCT) for locating the sectioning site of a specimen before characterizing the ultrastructural features of dentin surfaces as well as the inner wall of the dentinal tubules (DT) using a field emission scanning electron microscope (FESEM). Eight sound human molar teeth were extracted, examined via cross-polarization optical coherence tomography (CP-OCT), embedded, and hemisectioned using a low-speed diamond sawing machine. Next, each sectioned surface was further trimmed, polished, and examined under a confocal laser scanning microscope (CLSM) to locate the target area on the superficial dentin. Subsequently, each section ...

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    4. The effects of electrical pulses-mediated gold and silver nanoparticles on the optical properties of ex vivo human femoral head tissue with optical coherence tomography

      The effects of electrical pulses-mediated gold and silver nanoparticles on the optical properties of ex vivo human femoral head tissue with optical coherence tomography

      This study aims to monitor and assess the penetration and accumulation of gold nanoparticles (Au NPs) or silver nanoparticles (Ag NPs) (average particle size 40 nm) and the penetration of the Au NPs or Ag NPs assisted by electrical impulses (EP) in human normal femoral head (NFH) and pathological femoral head (PFH) tissues. The results show that optical coherence tomography images can easily distinguish NFH from PFH tissues. The control group show that the average attenuation coefficient of NFH tissue is 4.895 mm −1 , and the average attenuation coefficient of PFH tissue is 8.094 mm −1 . It shows ...

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    5. Microstructural changes in rice (Oryza sativa L.) leaves under varying low pH levels: a swept-source optical coherence tomography approach

      Microstructural changes in rice (Oryza sativa L.) leaves under varying low pH levels: a swept-source optical coherence tomography approach

      Soil acidification has shown detrimental effects on rice plants that lead to decreased rice production. In the present study, we aim to study the microstructural changes in rice leaves under acidic stress through swept-source optical coherence tomography (SS-OCT). To achieve this, rice seeds were germinated, subsequently these germinated seedlings were further grown under varying pH conditions for 14 d. Growth in root and shoot of plants and chlorophyll content of leaf samples were studied at varying pH levels. Similarly, acidic stress treated rice leaves were also subjected to SS-OCT image analysis revealing several features present in the layers of leaves ...

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    6. A review of low-cost and portable optical coherence tomography

      A review of low-cost and portable optical coherence tomography

      Optical coherence tomography (OCT) is a powerful optical imaging technique capable of visualizing the internal structure of biological tissues at near cellular resolution. For years, OCT has been regarded as the standard of care in ophthalmology, acting as an invaluable tool for the assessment of retinal pathology. However, the costly nature of most current commercial OCT systems has limited its general accessibility, especially in low-resource environments. It is therefore timely to review the development of low-cost OCT systems as a route for applying this technology to population-scale disease screening. Low-cost, portable and easy to use OCT systems will be essential ...

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    7. Depth encoded input polarisation independent swept source cross-polarised optical coherence tomography probe

      Depth encoded input polarisation independent swept source cross-polarised optical coherence tomography probe

      Within the last decades, several studies have been published that prove the benefit of polarisation sensitive optical coherence (psOCT) tomography for the field of biomedical diagnostics. However, polarisation sensitive imaging typically requires careful control of the polarisation state of the input illumination, which leads to bulky and delicate systems. While psOCT provides quantitative information, it is mostly sufficient to analyse the images qualitatively in the field of biomedical diagnostics. Therefore, a reduced form of this technique, cross-polarised optical coherence tomography (cpOCT), moves into the focus of interest that serves to visualise the birefringence properties of a sample. Despite the low ...

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    8. Compressive sensing for polarization sensitive optical coherence tomography

      Compressive sensing for polarization sensitive optical coherence tomography

      In this work, we reported on the implementation of compressive sensing (CS) and sparse sampling in polarization - sensitive optical coherence tomography (PS-OCT) to reduce the number of B-scans (frames consisting of an array of A-scans, where each represents a single depth profile of reflections) required for effective volumetric (3D dataset composed of an array of B-scans) PS-OCT mea surements (i.e., OCT intensity, and phase retardation) reconstruction. Sparse sampling of PS-OCT is achieved through randomization of step sizes along slow-axis of PS-OCT imaging, covering the same spatial ranges as those with equal slow-axis step sizes, but with a reduced number ...

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    9. Design of 1300-nm spectral domain optical coherence tomography angiography system for iris microvascular imaging

      Design of 1300-nm spectral domain optical coherence tomography angiography system for iris microvascular imaging

      Developing a high-resolution non-invasive optical coherence tomography angiography (OCTA) method for iris vasculature imaging is essential for diagnosing a wide range of ocular pathologies. However, the current iris-OCTA devices are still limited in imaging quality and penetration depth for dark-colored eyes ranging from brown to dark brown. A spectral domain iris-OCTA system is presented in this paper incorporating a 1300 nm wavelength for deeper tissue penetration, a linear-wavenumber spectrometer for better detection sensitivity, and an iris scan objective lens for better optical focusing across the entire iris over a 12 × 12 mm2 scan field. The −6 dB fall-off range is ...

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    10. REAP: Revealing drug tolerant persister cells in cancer using contrast enhanced optical coherence and photoacoustic tomography

      REAP: Revealing drug tolerant persister cells in cancer using contrast enhanced optical coherence and photoacoustic tomography

      Despite chemotherapy, residual tumors often rely on so-called drug tolerant persister (DTP) cells, which evade treatment to give rise to therapy-resistant relapse and refractory disease. Detection of residual tumor cells proves to be challenging because of the rarity and heterogeneity of DTP cells. In the framework of a H2020 project, REAP will gather researchers and engineers from six countries, who will combine their expertise in biology, chemistry, oncology, material sciences, photonics, and electrical and biomedical engineering in the hope of revealing DTPs in cancer using contrast enhanced multimodal optical imaging. Laser sources for photoacoustic microscopy (PAM), photoacoustic tomography (PAT), and ...

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    11. Long-term in vivo monitoring of gliotic sheathing of ultrathin entropic coated brain microprobes with fiber-based optical coherence tomography

      Long-term in vivo monitoring of gliotic sheathing of ultrathin entropic coated brain microprobes with fiber-based optical coherence tomography

      Microfabricated neuroprosthetic devices have made possible important observations on neuron activity; however, long-term high-fidelity recording performance of these devices has yet to be realized. Tissue-device interactions appear to be a primary source of lost recording performance. The current state of the art for visualizing the tissue response surrounding brain implants in animals is Immunohistochemistry + Confocal Microscopy, which is mainly performed after sacrificing the animal. Monitoring the tissue response as it develops could reveal important features of the response which may inform improvements in electrode design. Optical Coherence Tomography (OCT), an imaging technique commonly used in ophthalmology, has already been adapted ...

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    12. 1.1 μm waveband tunable laser using emission-wavelength-controlled InAs quantum dots for swept-source optical coherence tomography applications

      1.1 μm waveband tunable laser using emission-wavelength-controlled InAs quantum dots for swept-source optical coherence tomography applications

      In this study, an optical gain chip using emission-wavelength-controlled self-assembled InAs quantum dots (QDs) was developed for swept-source optical coherence tomography (SS-OCT) applications. The optical characterizations indicated that the QDs emission wavelength and optical gain spectra were controlled in the 1.1 μ m waveband by optimizing the QDs growth conditions. This waveband is useful for obtaining a large imaging depth of OCT because of an optimal balance between absorption and scattering in biological samples. In addition, continuous tunable lasing in the waveband was achieved by introducing the QD-based gain chip into a grating-coupled external cavity. This tunable laser was introduced ...

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    13. Characterizing Rayleigh wave and longitudinal shear wave propagation for measurements of elastic moduli using optical coherence elastography

      Characterizing Rayleigh wave and longitudinal shear wave propagation for measurements of elastic moduli using optical coherence elastography

      Optical coherence elastography based on the measurements of elastic wave speeds can quantify elastic moduli in the wave propagation directions and provide high-resolution elasticity maps for tissue. Here, we simultaneously visualized a longitudinal shear wave propagating along the depth and a Rayleigh wave propagating in the lateral direction, and analyzed the propagation characteristics of the elastic waves, including group speeds, frequency spectra, and frequency-dependent wave speeds. The analysis of the propagation characteristics demonstrates the reliability of the elasticity quantification by measuring different types of speeds of the elastic waves.

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    14. Cross-sectional imaging through scattering media by quantum-mimetic optical coherence tomography with wavefront shaping

      Cross-sectional imaging through scattering media by quantum-mimetic optical coherence tomography with wavefront shaping

      Quantum-mimetic (QM) optical coherence tomography (OCT) combined with wavefront shaping is proposed as a novel approach to achieve high-resolution cross-sectional imaging through a strongly scattering medium. Specifcally, QM-OCT is a recently devised OCT technique mimicking quantum OCT to acquire its main characteristic features, most notably immunity to group-velocity dispersion and enhancement of axial resolution, without quantum light. To validate the proposed method, we demonstrate experimentally that a one-dimensional cross-sectional image of a sample located behind a diffuser plate is obtained successfully and efficiently with QM-OCT by shaping the wavefront of light incident onto the diffuser.

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    15. Machine learning aided automated differential diagnostics of chronic rhinitis based on optical coherence tomography

      Machine learning aided automated differential diagnostics of chronic rhinitis based on optical coherence tomography

      Chronic rhinitis (CR) is among the most frequent inflammatory diseases of ear-nose-throat (ENT) covering up to 30% of the population. Different forms of CR require different treatment tactics, which indicates the need for an efficient tool for differential diagnostics of CR. Optical coherence tomography (OCT) is a promising tool for fast non-invasive evaluation of nasal mucosa, which, however, requires further interpretation of the obtained diagnostic image. In this paper, we provide a comparative analysis of several machine learning approaches that aim at automated differential diagnostics of CR based on diagnostic OCT images of 78 patients aged between 28 and 74 ...

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    16. Convolutional neural network-based automatic detection of follicle cells in ovarian tissue using optical coherence tomography

      Convolutional neural network-based automatic detection of follicle cells in ovarian tissue using optical coherence tomography

      To preserve the fertility of young female cancer patients, ovarian tissue cryopreservation and transplantation have been investigated as next-generation reproductive medical technologies. Non-invasive visualization of follicles in ovarian tissue and cryopreservation of higher density tissue is essential for effective transplantation. We proposed the use of optical coherence tomography (OCT) that can noninvasively visualize the internal structure of the ovarian tissue. However, a method for quantifying cell density has not yet been established because of the lack of available techniques to visualize follicles noninvasively. We proposed the use of a convolutional neural network (CNN) to extract small features from medical images ...

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    17. Generative adversarial network–convolution neural network based breast cancer classification using optical coherence tomographic images

      Generative adversarial network–convolution neural network based breast cancer classification using optical coherence tomographic images

      Currently, breast tissue images are primarily classified by pathologists, which is time-consuming and subjective. Deep learning, however, can perform this task with the utmost precision. In order to achieve an improved performance, a large number of annotated datasets are required to train the network, which is a challenging task in the medical field. In this paper, we propose an intelligent system, based on generative adversarial networks (GANs) and a convolution neural network (CNN) for the automatic classification of breast cancer, using optical coherence tomography (OCT) images. In this network, the GAN is used to generate synthetic datasets and to further ...

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    18. Slow axis displacement correction for stripe artefact removal in optical coherence angiography

      Slow axis displacement correction for stripe artefact removal in optical coherence angiography

      The method for displacement correction along the slow axis of optical coherence tomography (OCT) data volumes is presented. The method is based on the recursive replacement of the next displaced OCT measurements by the weighted summation of itself and the previous OCT measurement in the slow axis dimension already corrected for the displacement. The values of the appropriate weight multipliers were defined from the local correlation of the two measurements. The proposed method was used as a preprocessing step for optical coherence angiography processing of the OCT data. A substantial reduction of the motion-induced stripe artifact was demonstrated.

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    19. An imaging analysis and reconstruction method for multiple-micro-electro-mechanical system mirrors-based off-centre scanning optical coherence tomography probe

      An imaging analysis and reconstruction method for multiple-micro-electro-mechanical system mirrors-based off-centre scanning optical coherence tomography probe

      An endoscopic optical coherence tomography (OCT) probe that can perform full circumferential scans using a circular array of six micro-electro-mechanical system (MEMS) mirrors has been developed. Inside the OCT probe, each of the six MEMS mirrors forms an independent scanning unit; circumferential OCT images are acquired by off-centre scanning and combining the image data from the individual multiple scanning units. Here, an imaging analysis and reconstruction (IAR) method is proposed to construct endoscopic OCT volumetric images from the multiple individual MEMS scanning unit. Imaging procedures of six-MEMS mirrors-based, eight-MEMS mirrors-based and twelve-MEMS mirrors-based OCT probes have been analyzed theoretically. All ...

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    20. Direct en-face, speckle-reduced images using angular-compounded Master–Slave optical coherence tomography

      Direct en-face, speckle-reduced images using angular-compounded Master–Slave optical coherence tomography

      In this paper, an angular compounding method to achieve speckle contrast reduction in optical coherence tomography (OCT) imaging is explored in detail. The angular compounding approach involves collecting multiple images at different angles of incidence, registering the images to correct for induced distortions, and then incoherently summing the images to reduce speckle. The method was experimentally demonstrated with a spectrometer-based Master–Slave enhanced OCT instrument capable of directly generating en-face images. We have investigated the impact of the angular range and number of averaged frames on the degree of speckle artefact reduction, as well as the effect on image resolution ...

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    21. Wavelength-encoded multi-channel spectral-domain optical coherence tomography (SD-OCT) for spatiotemporally resolved imaging

      Wavelength-encoded multi-channel spectral-domain optical coherence tomography (SD-OCT) for spatiotemporally resolved imaging

      In conventional SD-OCT, a beam is focused to one spot on the surface of the sample to acquire depth information beneath that spot. Adjacent spots are serially scanned to obtain a tomographic image of the sample; thus, available OCT techniques can take significant time to scan large objects. This paper illustrates an SD-OCT system involving spectral-slicing of a broadband spectrum to enable the simultaneous acquisition from multiple lateral positions of the sample. Using a wavelength encoding of spatial information, where each lateral location is associated with a specific portion of a source spectrum, multiple lateral spots are interrogated concurrently to ...

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    22. Direct en-face, speckle-reduced images using angular-compounded Master-Slave optical coherence tomography

      Direct en-face, speckle-reduced images using angular-compounded Master-Slave optical coherence tomography

      In this paper, an angular compounding method to achieve speckle contrast reduction in optical coherence tomography (OCT) imaging is explored in detail. The angular compounding approach involves collecting multiple images at different angles of incidence, registering the images to correct for induced distortions, and then incoherently summing the images to reduce speckle. The method was experimentally demonstrated with a spectrometer-based Master-Slave enhanced OCT instrument capable of directly generating en-face images. We have investigated the impact of the angular range and number of averaged frames on the degree of speckle artefact reduction, as well as the effect on image resolution and ...

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    23. Identification of atherosclerotic plaques in intravascular optical coherence tomography images based on textures and artificial neural network

      Identification of atherosclerotic plaques in intravascular optical coherence tomography images based on textures and artificial neural network

      Intravascular optical coherence tomography (IVOCT) is becoming an important choice for in vivo diagnosis of coronary artery diseases. The atherosclerotic disease can be detected from IVOCT images, but the segmentation of IVOCT images and identification of plaques are mainly performed manually. This process is laborious and time consuming and its accuracy relies on the expertise of the observer. To address these limitations, a semi-automated identification algorithm based on texture features is presented in this paper. Regions of interest (ROIs) in IVOCT images are firstly selected, then texture features are calculated to represent this ROI. Finally, an artificial neural network is ...

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    24. Swept source cross-polarized optical coherence tomography for any input polarized light

      Swept source cross-polarized optical coherence tomography for any input polarized light

      Cross polarized optical coherence tomography offers enhanced contrast in certain pathological conditions. Traditional cross-polarized optical coherence tomography systems require a defined input polarization and thus require several polarization controlling elements increasing the overall complexity of the system. Our proposed system requires a single quarter wave plate as a polarization controller thus simplifying the system significantly. Majority of Cross-polarized optical coherence tomography systems are spectrometer based which suffers from slow speed and low signal to noise ratio. In this work, we present a swept source based cross-polarized optical coherence tomography system that works for any input polarization state. The system was ...

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