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    1. Contrastive uncertainty based biomarkers detection in retinal optical coherence tomography images

      Contrastive uncertainty based biomarkers detection in retinal optical coherence tomography images

      Retinal biomarker in optical coherence tomography (OCT) images plays a key guiding role in the follow-up diagnosis and clinical treatment of eye diseases. Although there have been many deep learning methods to automatically process retinal biomarker, the detection of retinal biomarkers is still a great challenge due to the similar characteristics to normal tissue, large changes in size and shape and fuzzy boundary of different types of biomarkers. To overcome these challenges, a novel contrastive uncertainty network (CUNet) is proposed for retinal biomarkers detection in OCT images. In CUNet, proposal contrastive learning is designed to enhance the feature representation of ...

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    2. Theory of sleep/wake cycles affecting brain elastography

      Theory of sleep/wake cycles affecting brain elastography

      As elastography of the brain finds increasing clinical applications, fundamental questions remain about baseline viscoelastic properties of the brain in vivo. Furthermore, the underlying mechanisms of how and why elastographic measures can change over time are still not well understood. To study these issues, reverberant shear wave elastography using an optical coherence tomography scanner is implemented on a mouse model, both under awake conditions and in a sleep state where there are known changes in the glymphatic fluid flow system in the brain. We find that shear wave speed, a measure of stiffness, changes by approximately 12% between the two ...

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    3. Attenuation coefficient for layer-by-layer assessment of the intestinal wall in acute ischemia according to optical coherence tomography

      Attenuation coefficient for layer-by-layer assessment of the intestinal wall in acute ischemia according to optical coherence tomography

      Small laboratory animals (rats) are suitable objects for modelling acute mesenteric ischemia (AMI) and monitoring changes in the structural tissue and intramural blood flow using optical coherence tomography (OCT) and OCT angiography methods. Combined with evaluation of blood circulation the prevalence of a necrotic tissue is a key factor in assessing intestine viability during surgery and determining the resection margins. While the assessment of the blood vessels network is commonly performed visually by surgeons, the assessment of the necrosis within individual layers is quite challenging due to small thickness of each intestine layer in small objects. The study demonstrates that ...

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    4. In situ volumetric imaging and analysis of FRESH 3D bioprinted constructs using optical coherence tomography

      In situ volumetric imaging and analysis of FRESH 3D bioprinted constructs using optical coherence tomography

      As 3D bioprinting has grown as a fabrication technology, so too has the need for improved analytical methods to characterize engineered constructs. This is especially challenging for engineered tissues composed of hydrogels and cells, as these materials readily deform when trying to assess print fidelity and other properties non-destructively. Establishing that the 3D architecture of the bioprinted construct matches its intended anatomic design is critical given the importance of structure-function relationships in most tissue types. Here we report development of a multimaterial bioprinting platform with integrated optical coherence tomography (OCT) for in situ volumetric imaging, error detection, and 3D reconstruction ...

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    5. Feature enhancement network for CNV typing in optical coherence tomography images

      Feature enhancement network for CNV typing in optical coherence tomography images

      Objective: Choroidal neovascularization (CNV) is a characteristic feature of wet age related macular degeneration (AMD), which is one of the main causes of blindness in the elderly. Automatic classification of CNV in optical coherence tomography (OCT) images plays an auxiliary role in the clinical treatment of CNV. Approach: This study proposes a feature enhancement network (FE-net) to discriminate between different CNV types with high inter-class similarity. The FE-net consists of two branches: discriminative FE and diverse FE. In the discriminative FE branch, a novel class-specific feature extraction (CSFE) module is introduced to learn class-specific features, and the discriminative loss is ...

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    6. Multi-task generative adversarial network for retinal optical coherence tomography image denoising

      Multi-task generative adversarial network for retinal optical coherence tomography image denoising

      Objective: Optical coherence tomography (OCT) has become an essential imaging modality for the assessment of ophthalmic diseases. However, speckle noise in OCT images obscures subtle but important morphological details and hampers its clinical applications. In this work, a novel multi-task generative adversarial network (MGAN) is proposed for retinal OCT image denoising. Approach: To strengthen the preservation of retinal structural information in the OCT denoising procedure, the proposed MGAN integrates adversarial learning and multi-task learning. Specifically, the generator of MGAN simultaneously undertakes two tasks, including the denoising task and the segmentation task. The segmentation task aims at the generation of the ...

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    7. Registration of histological brain images onto optical coherence tomography images based on shape information

      Registration of histological brain images onto optical coherence tomography images based on shape information

      Identifying tumour infiltration zones during tumour resection in order to excise as much tumour tissue as possible without damaging healthy brain tissue is still a major challenge in neurosurgery. The detection of tumour infiltrated regions so far requires histological analysis of biopsies taken from at expected tumour boundaries. The gold standard for histological analysis is the staining of thin cut specimen and the evaluation by a neuropathologist. This work presents a way to transfer the histological evaluation of a neuropathologist onto optical coherence tomography (OCT) images. OCT is a method suitable for real time in vivo imaging during neurosurgery however ...

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    8. Cross-free in both lateral and axial directions Fourier-domain full-field optical coherence tomography

      Cross-free in both lateral and axial directions Fourier-domain full-field optical coherence tomography

      Fourier-domain full-field optical coherence tomography (FD-FF-OCT) has the advantages of high resolution and parallel detection. However, using parallel detection can result in optical crosstalk. Toward minimizing crosstalk, we implemented a very fast deformable membrane (DM) that introduces random phase illumination, which can effectively reduce the crosstalk by washing out fringes originating from multiply scattered light. However, for one thing, although the application of DM has reduced the crosstalk problem in parallel detection to a certain extent, there will still be a lot of background noises, which may come from the circadian rhythm of the sample and multiple scattered photons. The ...

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    9. Photo Acoustic and Optical Coherence Tomography Imaging, Volume 3

      Photo Acoustic and Optical Coherence Tomography Imaging, Volume 3

      This book covers the state-of-the-art techniques of optical coherence tomography angiography (OCTA) imaging for the diagnosis of retinal diseases. It is part of a three-volume work that describes the latest imaging techniques in which to bring optical coherence tomography (OCT), Fundus Imaging and optical coherence tomography angiography (OCTA) to accurately facilitate the diagnosis of retinal diseases. Clinical disorders of the retina have been attracting the attention of researchers, aiming at reducing the blindness rate. This includes uveitis, diabetic retinopathy, macular edema, endophthalmitis, proliferative retinopathy, age-related macular degeneration and glaucoma. Treatment is significantly dependent on having early and accurate diagnosis, which ...

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    10. Automated segmentation of metal stent and bioresorbable vascular scaffold in intravascular optical coherence tomography images using deep learning architectures

      Automated segmentation of metal stent and bioresorbable vascular scaffold in intravascular optical coherence tomography images using deep learning architectures

      Percutaneous Coronary Intervention (PCI) with stent placement is a treatment effective for coronary artery diseases. Intravascular optical coherence tomography (OCT) with high resolution is used clinically to visualize stent deployment and restenosis, facilitating PCI operation and for complication inspection. Automated stent struts segmentation in OCT images is necessary as each pullback of OCT images could contain thousands of stent struts. In this paper, a deep learning framework is proposed and demonstrated for the automated segmentation of two major clinical stent types: metal stents and bioresorbable vascular scaffolds (BVS). U-Net, the current most prominent deep learning network in biomedical segmentation, was ...

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    11. Group-wise context selection network for choroid segmentation in optical coherence tomography

      Group-wise context selection network for choroid segmentation in optical coherence tomography

      Choroid thickness measured from optical coherence tomography (OCT) images has emerged as a vital metric in the management of retinal diseases such as high myopia. In this paper, we propose a novel group-wise context selection network (referred to as GCS-Net) to segment the choroid of either normal or high myopia eyes. To deal with the diverse choroid thickness and the variable shape of the pathological retina, GCS-Net adopts the group-wise channel dilation (GCD) module and the group-wise spatial dilation (GSD) module, which can automatically select group-wise multi-scale information under the guidance of channel attention or spatial attention, and enhance the ...

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    12. Differentiation between normal and tumor mammary glands with depth-resolved attenuation coefficient from optical coherence tomography

      Differentiation between normal and tumor mammary glands with depth-resolved attenuation coefficient from optical coherence tomography

      Optical coherence tomography (OCT) is a well-established imaging technology for high-resolution, cross-sectional imaging of biological tissues. Imaging processing and light attenuation coefficient estimation allows to further improve the OCT diagnostic capability. In this paper we use a commercial OCT system, Telesto II-1325LR from Thorlabs, and demonstrate its ability to differentiate normal and tumor mammary mouse glands with the OCT attenuation coefficient. Using several OCT images of normal and tumor mammary mouse glands (n=26), a statistical analysis was performed. The attenuation coefficient was calculated in depth, considering a slope of 0.5 mm. The normal glands present a median attenuation ...

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      Mentions: Thorlabs
    13. Unsupervised domain adaptation model for lesion detection in retinal OCT images

      Unsupervised domain adaptation model for lesion detection in retinal OCT images

      Background and objective Optical Coherence Tomography (OCT) is one of the most used retinal imaging modalities in the clinic as it can provide high-resolution anatomical images. The huge number of OCT images has significantly advanced the development of deep learning methods for automatic lesion detection to ease the doctor's workload. However, it has been frequently revealed that the deep neural network (DNN) model has difficulty handling the domain discrepancies, which widely exist in medical images captured from different devices. Many works have been proposed to solve the domain shift issue in deep learning tasks such as disease classification and ...

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    14. Correction of refractive and scattered image distortions in optical coherence tomography based on scalpel

      Correction  of  refractive  and  scattered  image  distortions  in optical coherence tomography based on scalpel

      Optical coherence tomography (OCT) is a non-invasive imaging te chnique, which has high resolution and high sensitivity. Due to its real-time, cross-sectional, an d micrometer-scale imaging capabilities, OCT has been widely used in ophthalmology [1]. In ophthalmic im aging, OCT allowed for not only the analysis of anterior segment structures like cornea and iri s, but also the visualization of details like trabecular meshwork and Schlemm’s canal. Clinically, real-time OCT images help surgeons to evaluate the lesion and plan surgical paths. With the developme nt of swept-source optical coherence tomography (SS-OCT), the axial scanning speed has reached multi -MHz ...

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    15. 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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    16. 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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    17. 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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    18. 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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    19. 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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    20. 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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    21. 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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    22. 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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    23. 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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    24. 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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