1. 1-24 of 554 1 2 3 4 ... 21 22 23 »
    1. OCT particle tracking velocimetry of biofluids in a microparallel plate strain induction chamber

      OCT particle tracking velocimetry of biofluids in a microparallel plate strain induction chamber

      Significance: Imaging biofluid flow under physiologic conditions aids in understanding disease processes and health complications. We present a method employing a microparallel plate strain induction chamber (MPPSIC) amenable to optical coherence tomography to track depth-resolved lateral displacement in fluids in real time while under constant and sinusoidal shear. Aim: Our objective is to track biofluid motion under shearing conditions found in the respiratory epithelium, first validating methods in Newtonian fluids and subsequently assessing the capability of motion-tracking in bronchial mucus. Approach: The motion of polystyrene microspheres in aqueous glycerol is tracked under constant and sinusoidal applied shear rates in the ...

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    2. Automatic focus method using interference fringes magnitudes in retinal optical coherence tomography

      Automatic focus method using interference fringes magnitudes in retinal optical coherence tomography

      In retinal optical coherence tomography (OCT), it is significant to focus the scan beam on the retina layers of the human eye fast to acquire high-quality OCT images. The refrac- tive errors of the human eye are usually compensated by shifting the optical lens in the sample arm manually or electrically. Otherwise, refractive errors of the human eye will cause axial focal shift of the scanning beam and blur the OCT images. We propose a fast automatic focus method using the interference fringes magnitudes of the whole retinal layers to determine the best refrac- tive correction position of motor-driven optical ...

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    3. MEMS-VCSEL as a tunable light source for OCT imaging of long working distance

      MEMS-VCSEL as a tunable light source for OCT imaging of long working distance

      We present a wavelength tunable vertical-cavity surface-emitting laser (VCSEL) constructed by die-bonding a half-cavity InGaAs laser diode (LD) chip onto a silicon-on-insulator chip with a microelectromechanical system electrostatic diaphragm mirror that functions as a Fabry–Perot interferometer. As a result of the short cavity length, the integrated tunable LD has single-mode lasing characteristics with an extremely large coherence length of 150 m or more. The developed wavelength tunable LD is used to perform swept-source optical coherence tomography with a large scan depth, which is applicable to ophthalmic observation for the diagnosis of pathologic nearsightedness based on the measurement of the ...

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      Mentions: Santec
    4. Automatic quantitative analysis of structure parameters in the growth cycle of artificial skin using optical coherence tomography

      Automatic quantitative analysis of structure parameters in the growth cycle of artificial skin using optical coherence tomography

      Significance: Artificial skin (AS) is widely used in dermatology, pharmacology, and toxicology, and has great potential in transplant medicine, burn wound care, and chronic wound treatment. There is a great demand for high-quality AS product and a non-invasive detection method is highly desirable. Aim: To quantify the constructure parameters (i.e., thickness and surface roughness) of AS samples in the culture cycle and explore the growth regularities using optical coherent tomography (OCT). Approach: An adaptive interface detection algorithm is developed to recognize surface points in each A-scan, offering a rapid method to calculate parameters without constructing OCT B-scan pictures and ...

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    5. Surface kinematic and depth-resolved analysis of human vocal folds in vivo during phonation using optical coherence tomography

      Surface kinematic and depth-resolved analysis of human vocal folds in vivo during phonation using optical coherence tomography

      Significance: The human vocal fold (VF) oscillates in multiple vectors and consists of distinct layers with varying viscoelastic properties that contribute to the mucosal wave. Office-based and operative laryngeal endoscopy are limited to diagnostic evaluation of the VF epithelial surface only and are restricted to axial-plane characterization of the horizontal mucosal wave. As such, understanding of the biomechanics of human VF motion remains limited. Aim: Optical coherence tomography (OCT) is a micrometer-resolution, high-speed endoscopic imaging modality which acquires cross-sectional images of tissue. Our study aimed to leverage OCT technology and develop quantitative methods for analyzing the anatomy and kinematics of ...

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    6. Looking for a perfect match: multimodal combinations of Raman spectroscopy for biomedical applications

      Looking for a perfect match: multimodal combinations of Raman spectroscopy for biomedical applications

      Raman spectroscopy has shown very promising results in medical diagnostics by providing label-free and highly specific molecular information of pathological tissue ex vivo and in vivo . Nevertheless, the high specificity of Raman spectroscopy comes at a price, i.e., low acquisition rate, no direct access to depth information, and limited sampling areas. However, a similar case regarding advantages and disadvantages can also be made for other highly regarded optical modalities, such as optical coherence tomography, autofluorescence imaging and fluorescence spectroscopy, fluorescence lifetime microscopy, second-harmonic generation, and others. While in these modalities the acquisition speed is significantly higher, they have no ...

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    7. Concurrent OCT and OCT angiography of retinal neurovascular degeneration in the 5XFAD Alzheimer’s disease mice

      Concurrent OCT and OCT angiography of retinal neurovascular degeneration in the 5XFAD Alzheimer’s disease mice

      Significance : As one part of the central nervous system, the retina manifests neurovascular defects in Alzheimer’s disease (AD). Quantitative imaging of retinal neurovascular abnormalities may promise a new method for early diagnosis and treatment assessment of AD. Previous imaging studies of transgenic AD mouse models have been limited to the central part of the retina. Given that the pathological hallmarks of AD frequently appear in different peripheral quadrants, a comprehensive regional investigation is needed for a better understanding of the retinal degeneration associated with AD-like pathology. Aim : We aim to demonstrate concurrent optical coherence tomography (OCT) and OCT angiography ...

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    8. Label-free detection of brain tumors in a 9L gliosarcoma rat model using stimulated Raman scattering-spectroscopic optical coherence tomography

      Label-free detection of brain tumors in a 9L gliosarcoma rat model using stimulated Raman scattering-spectroscopic optical coherence tomography

      Significance: In neurosurgery, it is essential to differentiate between tumor and healthy brain regions to maximize tumor resection while minimizing damage to vital healthy brain tissue. However, conventional intraoperative imaging tools used to guide neurosurgery are often unable to distinguish tumor margins, particularly in infiltrative tumor regions and low-grade gliomas. Aim: The aim of this work is to assess the feasibility of a label-free molecular imaging tool called stimulated Raman scattering-spectroscopic optical coherence tomography (SRS-SOCT) to differentiate between healthy brain tissue and tumor based on (1) structural biomarkers derived from the decay rate of signals as a function of depth ...

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      Mentions: Emory University
    9. Small airway dilation measured by endoscopic optical coherence tomography correlates with chronic lung allograft dysfunction

      Small airway dilation measured by endoscopic optical coherence tomography correlates with chronic lung allograft dysfunction

      Significance: Chronic lung allograft dysfunction (CLAD) is the leading cause of death in transplant patients who survive past the first year post-transplant. Current diagnosis is based on sustained decline in lung function; there is a need for tools that can identify CLAD onset. Aim: Endoscopic optical coherence tomography (OCT) can visualize structural changes in the small airways, which are of interest in CLAD progression. We aim to identify OCT features in the small airways of lung allografts that correlate with CLAD status. Approach: Imaging was conducted with an endoscopic rotary pullback OCT catheter during routine bronchoscopy procedures (n = 54), collecting ...

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    10. CNN-based CP-OCT sensor integrated with a subretinal injector for retinal boundary tracking and injection guidance

      CNN-based CP-OCT sensor integrated with a subretinal injector for retinal boundary tracking and injection guidance

      Significance: Subretinal injection is an effective way of delivering transplant genes and cells to treat many degenerative retinal diseases. However, the technique requires high-dexterity and microscale precision of experienced surgeons, who have to overcome the physiological hand tremor and limited visualization of the subretinal space. Aim: To automatically guide the axial motion of microsurgical tools (i.e., a subretinal injector) with microscale precision in real time using a fiber-optic common-path swept-source optical coherence tomography distal sensor. Approach: We propose, implement, and study real-time retinal boundary tracking of A-scan optical coherence tomography (OCT) images using a convolutional neural network (CNN) for ...

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    11. Fiber-based photoacoustic remote sensing microscopy and spectral-domain optical coherence tomography with a dual-function 1050-nm interrogation source

      Fiber-based photoacoustic remote sensing microscopy and spectral-domain optical coherence tomography with a dual-function 1050-nm interrogation source

      Significance: Spectral-domain optical coherence tomography (SD-OCT) offers depth-resolved imaging of optical scattering contrast but is limited in sensitivity to optical absorption. Dual-modality imaging combined with the noncontact absorption contrast of photoacoustic remote sensing (PARS) microscopy can augment SD-OCT applications with specific molecular and functional contrasts in an all-optical, fiber-based platform. Aim: To develop a fiber-based multimodal PARS and SD-OCT imaging system, which efficiently uses a common 1050-nm light source for SD-OCT and PARS interrogation. Approach: PARS microscopy has predominantly utilized a 1310-nm interrogation light source to date. Hence, a recent dual-modality PARS and 1050-nm SD-OCT imaging system required three distinct ...

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    12. Adaptive compounding speckle-noise-reduction filter for optical coherence tomography images

      Adaptive compounding speckle-noise-reduction filter for optical coherence tomography images

      Significance: Speckle noise limits the diagnostic capabilities of optical coherence tomography (OCT) images, causing both a reduction in contrast and a less accurate assessment of the microstructural morphology of the tissue. Aim: We present a speckle-noise reduction method for OCT volumes that exploits the advantages of adaptive-noise wavelet thresholding with a wavelet compounding method applied to several frames acquired from consecutive positions. The method takes advantage of the wavelet representation of the speckle statistics, calculated properly from a homogeneous sample or a region of the noisy volume. Approach: The proposed method was first compared quantitatively with different state-of-the-art approaches by ...

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    13. Minimally invasive intrathecal spinal cord imaging with optical coherence tomography

      Minimally invasive intrathecal spinal cord imaging with optical coherence tomography

      ignificance: Imaging of the spinal cord is challenging due to the surrounding bony anatomy, physiologic motion, and the small diameter of the spinal cord. This precludes the use of non-invasive imaging techniques in assessing structural changes related to trauma and evaluating residual function. Aim: The purpose of our research was to apply endovascular technology and techniques and construct a preclinical animal model of intrathecal spinal cord imaging using optical coherence tomography (OCT). Approach: Five animals (2 Yorkshire Swine and 3 New Zealand Rabbits) were utilized. Intrathecal access was gained using a 16-guage Tuohy, and an OCT catheter was advanced under ...

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    14. Dissecting the microvascular contributions to diffuse correlation spectroscopy measurements of cerebral hemodynamics using optical coherence tomography angiography

      Dissecting the microvascular contributions to diffuse correlation spectroscopy measurements of cerebral hemodynamics using optical coherence tomography angiography

      Significance: Diffuse correlation spectroscopy (DCS) is an emerging noninvasive, diffuse optical modality that purportedly enables direct measurements of microvasculature blood flow. Functional optical coherence tomography angiography (OCT-A) can resolve blood flow in vessels as fine as capillaries and thus has the capability to validate key attributes of the DCS signal. Aim: To characterize activity in cortical vasculature within the spatial volume that is probed by DCS and to identify populations of blood vessels that are most representative of the DCS signals. Approach: We performed simultaneous measurements of somatosensory-evoked cerebral blood flow in mice in vivo using both DCS and OCT-A ...

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      Mentions: FDA
    15. Deep feature loss to denoise OCT images using deep neural networks

      Deep feature loss to denoise OCT images using deep neural networks

      Significance: Speckle noise is an inherent limitation of optical coherence tomography (OCT) images that makes clinical interpretation challenging. The recent emergence of deep learning could offer a reliable method to reduce noise in OCT images. Aim: We sought to investigate the use of deep features (VGG) to limit the effect of blurriness and increase perceptual sharpness and to evaluate its impact on the performance of OCT image denoising (DnCNN). Approach: Fifty-one macula-centered OCT pairs were used in training of the network. Another set of 20 OCT pair was used for testing. The DnCNN model was cascaded with a VGG network ...

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    16. Quantitative assessment of retinal and choroidal blood vessels volume using a voxel processing of optical coherence tomography angiography images

      Quantitative assessment of retinal and choroidal blood vessels volume using a voxel processing of optical coherence tomography angiography images

      Recently, we have proposed a voxel processing algorithm of optical coherence tomography angiography (OCTA) images to increase the accuracy of quantitative assessment of retinal and choroidal blood vessels volume. The purpose of this is to ascertain the effectiveness of the algorithm and to use it for determining the volumetric flow index ratio of the vascular network in the choroid ( V Chor ) and the total vascular network ( V All ) across the retinal and choroidal layers. Five patients (seven eyes) aged 25 to 68 years without ophthalmic pathologies and nine patients (12 eyes) aged 64 to 79 years with stage II of ...

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    17. Common-path interferometer for digital holographic Doppler spectroscopy of living biological tissues

      Common-path interferometer for digital holographic Doppler spectroscopy of living biological tissues

      Significance: Common-path interferometers have the advantage of producing ultrastable interferometric fringes compared with conventional interferometers, such as Michelson or Mach–Zehnder that are sensitive to environmental instabilities. Isolating interferometric measurements from mechanical disturbances is important in biodynamic imaging because Doppler spectroscopy of intracellular dynamics requires extreme stability for phase-sensitive interferometric detection to capture fluctuation frequencies down to 10 mHz. Aim: The aim of this study was to demonstrate that Doppler spectra produced from a common-path interferometer using a grating and a spatial filter (SF) are comparable to, and more stable than, spectra from conventional biodynamic imaging. Approach: A common-path interferometer ...

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    18. Advantage of low NEP balanced receivers in swept source OCT

      Advantage of low NEP balanced receivers in swept source OCT

      Low NEP balanced receivers generally do not result in better sensitivity in a shot-noise-limited swept source OCT system. However, there is an advantage if RIN is significant. A lower NEP, even in the shot-noise-limited case, does allow for lower reference arm powers. This, in turn, reduces fixed pattern artifact signals caused by stray optical component reflections inside a swept source laser cavity. An NEP reduction of √10 allows the reference power to be reduced 10 dB while maintaining SNR. This reduces the pattern to noise ratio by 10 dB because pattern noise is directly detected (20 dB scaling per decade ...

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    19. OCT applications in optics R&D and manufacturing

      OCT applications in optics R&D and manufacturing

      Optical coherence tomography (OCT) can be an important diagnostic tool in optics R&D and manufacturing. We illustrate this with four applications. (1) Imaging of vibration modes of MEMS membranes. (2) Strain mapping of VCSEL chips. (3) Optical frequency domain reflectometry (OFDR) of laser cavities. (4) Combined responsivity and 3D mapping of photodiode packages.

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    20. Measuring myelin content and cell density in the human brain using optical coherence tomography

      Measuring myelin content and cell density in the human brain using optical coherence tomography

      Serial Sectioning Optical Coherence Tomography(serial sectioning OCT) has been widely used to investigate the structural and pathological features of brain samples. OCT is an optical imaging technique that provides both the 3D structure of the tissue as well as the optical properties including the scattering coefficient (μ s ) and back-scattering coefficient (μ b ). Serial sectioning OCT allows the reconstruction of distortion-free volumetric images at high contrast and high resolution, which has proven to be useful for the detection of cancerous tissue boundaries, visualizing 3D vascular structures and measuring neuron density. The tissue optical properties extracted from the OCT depth profile has ...

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    21. In vivo dual-mode full-field optical coherence tomography for differentiation of types of melanocytic nevi

      In vivo dual-mode full-field optical coherence tomography for differentiation of types of melanocytic nevi

      Significance: Melanocytic nevi represent the most common dermal melanocytic lesions in humans. Nevus is typically diagnosed clinically with the naked eye or with dermoscopy. However, it is essential to identify the type of nevus by invasive biopsy for histopathological examination. The use of noninvasive imaging tools can be used to evaluate the types of nevi to reduce unnecessary excisions of benign entities. Aim: To evaluate the feasibility of using en face and cross-sectional full-field optical coherence tomography (FF-OCT) in differentiation of melanocytic nevi that can facilitate the reduction of unnecessary excisions of benign entities. Approach: Dual-mode Mirau-type FF-OCT for cross-sectional ...

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    22. Heartbeat optical coherence elastography: corneal biomechanics in vivo

      Heartbeat optical coherence elastography: corneal biomechanics in vivo

      Significance: Mechanical assessment of the cornea can provide important structural and functional information regarding its health. Current clinically available tools are limited in their efficacy at measuring corneal mechanical properties. Elastography allows for the direct estimation of mechanical properties of tissues in vivo but is generally performed using external excitation force. Aim: To show that heartbeat optical coherence elastography (Hb-OCE) can be used to assess the mechanical properties of the cornea in vivo. Approach: Hb-OCE was utilized to detect Hb-induced deformations in the rabbit cornea in vivo without the need for external excitation. Furthermore, we demonstrate how this technique can ...

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    23. Improved sensitivity roll-off in dual reference, buffered spectral-domain optical coherence tomography

      Improved sensitivity roll-off in dual reference, buffered spectral-domain optical coherence tomography

      Significance: While spectral-domain optical coherence tomography (SD-OCT) is a preferred form of OCT imaging, sensitivity roll-off limits its applicability for certain biomedical imaging applications. Aim: The aim of this work is to extend the imaging range of conventional SD-OCT systems for imaging large luminal organs such as the gastrointestinal tract. Approach: We present an SD-OCT system operating at a center wavelength of 1300 nm that uses two delayed reference arms to reduce sensitivity roll-off and an optical switch and a fiber optic delay line to ensure that the interference spectra are acquired from the same sample time window. Result: The ...

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    24. Multi-reference global registration of individual A-lines in adaptive optics optical coherence tomography retinal images

      Multi-reference global registration of individual A-lines in adaptive optics optical coherence tomography retinal images

      Significance: Adaptive optics optical coherence tomography (AO-OCT) technology enables non-invasive, high-resolution three-dimensional (3D) imaging of the retina and promises earlier detection of ocular disease. However, AO-OCT data are corrupted by eye-movement artifacts that must be removed in post-processing, a process rendered time-consuming by the immense quantity of data. Aim: To efficiently remove eye-movement artifacts at the level of individual A-lines, including those present in any individual reference volume. Approach: We developed a registration method that cascades (1) a 3D B-scan registration algorithm with (2) a global A-line registration algorithm for correcting torsional eye movements and image scaling and generating global ...

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