1. 1-24 of 467 1 2 3 4 ... 18 19 20 »
    1. Optical coherence tomography for dynamic axial correction of an optical end-effector for robot-guided surgical laser ablation

      Optical coherence tomography for dynamic axial correction of an optical end-effector for robot-guided surgical laser ablation

      Robot-guided laser ablation for surgical applications potentially offers many advantages compared to by-hand mechanical tissue cutting. However, given that tissue can be rough and/or uneven, ablation quality can be compromised if the beam waist deviates significantly from the target tissue surface. Therefore, we present a method that uses optical coherence tomography (OCT) for dynamic refocusing of robot-guided surgical laser ablation. A 7-DOF robotic manipulator with an OCT-equipped optical payload was used to simulate robotic guided laser osteotomy. M-mode OCT feedback is used for continuous surface detection to correct for axial deviations along the ablation path due to surface nonuniformity ...

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    2. Automatic detection of retinal regions using fully convolutional networks for diagnosis of abnormal maculae in optical coherence tomography images

      Automatic detection of retinal regions using fully convolutional networks for diagnosis of abnormal maculae in optical coherence tomography images

      In conventional retinal region detection methods for optical coherence tomography (OCT) images, many parameters need to be set manually, which is often detrimental to their generalizability. We present a scheme to detect retinal regions based on fully convolutional networks (FCN) for automatic diagnosis of abnormal maculae in OCT images. The FCN model is trained on 900 labeled age-related macular degeneration (AMD), diabetic macular edema (DME) and normal (NOR) OCT images. Its segmentation accuracy is validated and its effectiveness in recognizing abnormal maculae in OCT images is tested and compared with traditional methods, by using the spatial pyramid matching based on ...

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    3. Simple and robust calibration procedure for k-linearization and dispersion compensation in optical coherence tomography

      Simple and robust calibration procedure for k-linearization and dispersion compensation in optical coherence tomography

      In Fourier-domain optical coherence tomography (FD-OCT), proper signal sampling and dispersion compensation are essential steps to achieve optimal axial resolution. These calibration steps can be performed through numerical signal processing, but require calibration information about the system that may require lengthy and complex measurement protocols. We report a highly robust calibration procedure that can simultaneously determine correction vectors for nonlinear wavenumber sampling and dispersion compensation. The proposed method requires only two simple mirror measurements and no prior knowledge about the system’s illumination source or detection scheme. This method applies to both spectral domain and swept-source OCT systems. Furthermore, it ...

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    4. Optimization-based vessel segmentation pipeline for robust quantification of capillary networks in skin with optical coherence tomography angiography

      Optimization-based vessel segmentation pipeline for robust quantification of capillary networks in skin with optical coherence tomography angiography

      Optical coherence tomography angiography (OCTA) provides in-vivo images of microvascular perfusion in high resolution. For its application to basic and clinical research, an automatic and robust quantification of the capillary architecture is mandatory. Only this makes it possible to reliably analyze large amounts of image data, to establish biomarkers, and to monitor disease developments. However, due to its optical properties, OCTA images of skin often suffer from a poor signal-to-noise ratio and contain imaging artifacts. Previous work on automatic vessel segmentation in OCTA mostly focuses on retinal and cerebral vasculature. Its applicability to skin and, furthermore, its robustness against imaging ...

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    5. Comparison of tissue dispersion measurement techniques based on optical coherence tomography

      Comparison of tissue dispersion measurement techniques based on optical coherence tomography

      The effects of dispersion on optical coherence tomography (OCT) images have long been documented. The imbalance of spectral broadening, caused by dispersion mismatches in the two arms of the OCT interferometer, can result in significant resolution degradation. Efforts to correct this phenomenon have resulted in improved image quality using various techniques. However, dispersion is also present and varies in tissues. As a result, group velocity dispersion (GVD) can be used to detect changes in tissues and provide useful information for diagnosis. Several methods can be utilized to measure the GVD from OCT images: (i) the degradation of the point spread ...

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    6. Capabilities of Gabor-domain optical coherence microscopy for the assessment of corneal disease

      Capabilities of Gabor-domain optical coherence microscopy for the assessment of corneal disease

      To identify the microstructural modification of the corneal layers during the course of the disease, optical technologies have been pushing the boundary of innovation to achieve cellular resolution of deep layers of the cornea. Gabor-domain optical coherence microscopy (GD-OCM), an optical coherence tomography-based technique that can achieve an isotropic of ∼2-μm resolution over a volume of 1  mm  ×  1  mm  ×  1.2  mm, was developed to investigate the microstructural modifications of corneal layers in four common corneal diseases. Since individual layer visualization without cutting through several layers is challenging due to corneal curvature, a flattening algorithm was developed to ...

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    7. Normalized field autocorrelation function-based optical coherence tomography three-dimensional angiography

      Normalized field autocorrelation function-based optical coherence tomography three-dimensional angiography

      Optical coherence tomography angiography (OCTA) has been widely used for <i>en face</i> visualization of the microvasculature, but is challenged for real three-dimensional (3-D) topologic imaging due to the “tail” artifacts that appear below large vessels. Further, OCTA is generally incapable of differentiating descending arterioles from ascending venules. We introduce a normalized field autocorrelation function-based OCTA (<i>g</i><sub>1</sub>-OCTA), which minimizes the tail artifacts and is capable of distinguishing penetrating arterioles from venules in the 3-D image. <i>g</i><sub>1</sub>   (  τ  )   is calculated from repeated optical coherence tomography (OCT) acquisitions for each spatial ...

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    8. Slope-based segmentation of articular cartilage using polarization-sensitive optical coherence tomography phase retardation image

      Slope-based segmentation of articular cartilage using polarization-sensitive optical coherence tomography phase retardation image

      A segmentation method based on phase retardation measurements from polarization-sensitive optical coherence tomography (PS-OCT) is developed to differentiate the structural zones of articular cartilage. The organization of collagen matrix in articular cartilage varies over the different structural zones, generating different tissue birefringence. Analyzing the slope of the accumulated phase retardation at different depths can detect the variation in tissue birefringence and be used to segment the structural zones. The method is validated on phantoms composed of layers of different materials. Articular cartilage samples from adult swine are segmented with the method. The characteristics in each segmented zone are also examined ...

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    9. Optical coherence elastography of cold cataract in porcine lens

      Optical coherence elastography of cold cataract in porcine lens

      Cataract is one of the most prevalent causes of blindness around the world. Understanding the mechanisms of cataract development and progression is important for clinical diagnosis and treatment. Cold cataract has proven to be a robust model for cataract formation that can be easily controlled in the laboratory. There is evidence that the biomechanical properties of the lens can be significantly changed by cataract. Therefore, early detection of cataract, as well as evaluation of therapies, could be guided by characterization of lenticular biomechanical properties. In this work, we utilized optical coherence elastography (OCE) to monitor the changes in biomechanical properties ...

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    10. Optical phantoms for biomedical polarimetry: a review

      Optical phantoms for biomedical polarimetry: a review

      Calibration, quantification, and standardization of the polarimetric instrumentation, as well as interpretation and understanding of the obtained data, require the development and use of well-calibrated phantoms and standards. We reviewed the status of tissue phantoms for a variety of applications in polarimetry; more than 500 papers are considered. We divided the phantoms into five groups according to their origin (biological/nonbiological) and fundamental polarimetric properties of retardation, depolarization, and diattenuation. We found that, while biological media are generally depolarizing, retarding, and diattenuating, only one of all the phantoms reviewed incorporated all these properties, and few considered at least combined retardation ...

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    11. Temperature stabilized phase reference for MEMS based swept sources

      Temperature stabilized phase reference for MEMS based swept sources

      MEMS tunable lasers are not inherently phase stable because Brownian motion and drive electronics noise make the starting wavelength of the sweep unstable with respect to the electrical sweep trigger. A typical solution to the problem is to use a fiber Bragg reflector wavelength trigger. That is a sub-optimal solution since environmental changes can move both the Bragg peak and the k-clock phase. We have packaged temperature controlled trigger and clock etalons in a butterfly package to solve this environmental problem. By making the wide FSR trigger etalon from silicon and the narrow FSR clock etalon from fused silica, the ...

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    12. Tunable 1060nm VCSEL co-packaged with pump and SOA for OCT and LiDAR

      Tunable 1060nm VCSEL co-packaged with pump and SOA for OCT and LiDAR

      A 1060 nm optically pumped tunable VCSEL was formed from an InGaAs/AlGaAs/GaAs half-VCSEL bonded to a MEMS movable mirror on a silicon substrate. The VCSEL was co-packaged in a 14-pin butterfly module with an 825 nm pump laser and a 1060 nm semiconductor optical amplifier. The co-packaged device exhibited shot-noise-limited sensitivity with up to 50 mW output power and 75 nm tunability. Ophthalmic OCT, especially whole-eye imaging and ocular biometry, is considered the primary application of this device. However, we have also investigated LiDAR to greater than 10 meter ranges with non-mechanical beam steering through angular diffraction from ...

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    13. Dynamic light scattering optical coherence tomography to probe motion of subcellular scatterers

      Dynamic light scattering optical coherence tomography to probe motion of subcellular scatterers

      Optical coherence tomography (OCT) is used to provide anatomical information of biological systems but can also provide functional information by characterizing the motion of intracellular structures. Dynamic light scattering OCT was performed on intact, control MCF-7 breast cancer cells and cells either treated with paclitaxel to induce apoptosis or deprived of nutrients to induce oncosis. Autocorrelations (ACs) of the temporal fluctuations of OCT intensity signals demonstrate a significant decrease in decorrelation time after 24 h in both the paclitaxel-treated and nutrient-deprived cell groups but no significant differences between the two groups. The acquired ACs were then used as input for ...

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    14. Automated phase unwrapping in Doppler optical coherence tomography

      Automated phase unwrapping in Doppler optical coherence tomography

      Phase wrapping is a crucial issue in Doppler optical coherence tomography (OCT) and restricts its automatic implementation for clinical applications that quantify total retinal blood flow. We propose an automated phase-unwrapping technique that takes advantage of the parabolic profile of blood flow velocity in vessels. Instead of inspecting the phase shift manually, the algorithm calculates the gradient magnitude of the phase shift on the cross-sectional image and automatically detects the presence of phase wrapping. The voxels affected by phase wrapping are corrected according to the determined flow direction adjacent to the vessel walls. We validated this technique in the rodent ...

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    15. Redox imaging and optical coherence tomography of the respiratory ciliated epithelium

      Redox imaging and optical coherence tomography of the respiratory ciliated epithelium

      Optical coherence tomography (OCT) is an emerging technology for in vivo< airway and lung imaging. However, OCT lacks sensitivity to the metabolic changes caused by inflammation, which drives chronic respiratory diseases such as asthma and chronic obstructive pulmonary disorder. Redox imaging (RI) is a label-free technique that uses the autofluorescence of the metabolic coenzymes NAD(P)H and flavin adenine dinucleotide (FAD) to probe cellular metabolism and could provide complimentary information to OCT for airway and lung imaging. We demonstrate OCT and RI of respiratory ciliated epithelial function in ex vivo mouse tracheae. We applied RI to measure cellular metabolism ...

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    16. Evaluation of segmentation algorithms for optical coherence tomography images of ovarian tissue

      Evaluation of segmentation algorithms for optical coherence tomography images of ovarian tissue

      Ovarian cancer has the lowest survival rate among all gynecologic cancers predominantly due to late diagnosis. Early detection of ovarian cancer can increase 5-year survival rates from 40% up to 92%, yet no reliable early detection techniques exist. Optical coherence tomography (OCT) is an emerging technique that provides depth-resolved, high-resolution images of biological tissue in real-time and demonstrates great potential for imaging of ovarian tissue. Mouse models are crucial to quantitatively assess the diagnostic potential of OCT for ovarian cancer imaging; however, due to small organ size, the ovaries must first be separated from the image background using the process ...

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    17. Endoscopic optical coherence tomography with wide field-of-view for the morphological and functional assessment of the human tympanic membrane

      Endoscopic optical coherence tomography with wide field-of-view for the morphological and functional assessment of the human tympanic membrane

      An endoscopic optical coherence tomography (OCT) system with a wide field-of-view of 8 mm is presented, which combines the image capability of endoscopic imaging at the middle ear with the advantages of functional OCT imaging, allowing a morphological and functional assessment of the human tympanic membrane. The endoscopic tube has a diameter of 3.5 mm and contains gradient-index optics for simultaneous forward-viewing OCT and video endoscopy. The endoscope allows the three-dimensional visualization of nearly the entire tympanic membrane. In addition, the oscillation of the tympanic membrane is measured spatially resolved and in the frequency range between 500 Hz and ...

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    18. Deep neural networks for A-line-based plaque classification in coronary intravascular optical coherence tomography images

      Deep neural networks for A-line-based plaque classification in coronary intravascular optical coherence tomography images

      We develop neural-network-based methods for classifying plaque types in clinical intravascular optical coherence tomography (IVOCT) images of coronary arteries. A single IVOCT pullback can consist of >500 microscopic-resolution images, creating both a challenge for physician interpretation during an interventional procedure and an opportunity for automated analysis. In the proposed method, we classify each A-line, a datum element that better captures physics and pathophysiology than a voxel, as a fibrous layer followed by calcification (fibrocalcific), a fibrous layer followed by a lipidous deposit (fibrolipidic), or other. For A-line classification, the usefulness of a convolutional neural network (CNN) is compared with that ...

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    19. Fully automated dual-resolution serial optical coherence tomography aimed at diffusion MRI validation in whole mouse brains

      Fully automated dual-resolution serial optical coherence tomography aimed at diffusion MRI validation in whole mouse brains

      An automated dual-resolution serial optical coherence tomography (2R-SOCT) scanner is developed. The serial histology system combines a low-resolution (25  μm  /  voxel) 3  ×   OCT with a high-resolution (1.5  μm  /  voxel) 40  ×   OCT to acquire whole mouse brains at low resolution and to target specific regions of interest (ROIs) at high resolution. The 40  ×   ROIs positions are selected either manually by the microscope operator or using an automated ROI positioning selection algorithm. Additionally, a multimodal and multiresolution registration pipeline is developed in order to align the 2R-SOCT data onto diffusion MRI (dMRI) data acquired in the same ex vivo mouse brains ...

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    20. Integrated optical coherence tomography and multielement ultrasound transducer probe for shear wave elasticity imaging of moving tissues

      Integrated optical coherence tomography and multielement ultrasound transducer probe for shear wave elasticity imaging of moving tissues

      Accurate measurements of microelastic properties of soft tissues in-vivo using optical coherence elastography can be affected by motion artifacts caused by cardiac and respiratory cycles. This problem can be overcome using a multielement ultrasound transducer probe where each ultrasound transducer is capable of generating acoustic radiation force (ARF) and, therefore, creating shear waves in tissue. These shear waves, produced during the phase of cardiac and respiratory cycles when tissues are effectively stationary, are detected at the same observation point using phase-sensitive optical coherence tomography (psOCT). Given the known distance between the ultrasound transducers, the speed of shear wave propagation can ...

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    21. Line-field confocal optical coherence tomography for high-resolution noninvasive imaging of skin tumors

      Line-field confocal optical coherence tomography for high-resolution noninvasive imaging of skin tumors

      An optical technique called line-field confocal optical coherence tomography (LC-OCT) is introduced for high-resolution, noninvasive imaging of human skin in vivo . LC-OCT combines the principles of time-domain optical coherence tomography and confocal microscopy with line illumination and detection using a broadband laser and a line-scan camera. LC-OCT measures the echo-time delay and amplitude of light backscattered from cutaneous microstructures through low-coherence interferometry associated with confocal spatial filtering. Multiple A-scans are acquired simultaneously while dynamically adjusting the focus. The resulting cross-sectional B-scan image is produced in real time at 10  frame  /  s. With an isotropic spatial resolution of ∼1  μm, the ...

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    22. Combined anatomical optical coherence tomography and intraluminal pressure reveal viscoelasticity of the in vivo airway

      Combined anatomical optical coherence tomography and intraluminal pressure reveal viscoelasticity of the in vivo airway

      It is hypothesized that the local, viscoelastic (time-dependent) properties of the airway are important to accurately model and ultimately predict dynamic airway collapse in airway obstruction. Toward this end, we present a portable, endoscopic, swept-source anatomical optical coherence tomography (aOCT) system combined with a pressure catheter to capture local airway dynamics in vivo during respiration. aOCT scans were performed in the airways of a mechanically ventilated pig under paralysis with dynamic and static ventilation protocols. Validation of dynamic aOCT luminal cross-sectional area (CSA) measurements against Cine CT, obtained during the same exam, showed an aggregate difference of 15  %    ±  3  %  . aOCT-derived ...

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    23. Optical coherence tomography provides an optical biopsy of burn wounds in children—a pilot study

      Optical coherence tomography provides an optical biopsy of burn wounds in children—a pilot study

      Thermic injuries are among the most severe injuries in childhood. Burn depth is the most relevant prognostic factor, and still its assessment is both difficult and controversial. This diagnostic uncertainty results in repeated wound assessments over a 10-day period and carries a relevant risk for over- and undertreatment. Precise wound assessment would thus be a significant step toward improved care. Optical coherence tomography (OCT) is a noninvasive laser-based technique with a penetration depth of ∼2  mm. It provides structural images of the skin while dynamic OCT (D-OCT) shows blood vessels. In this study, we investigated burns and scalds in 130 ...

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    24. Preclinical quantitative in-vivo assessment of skin tissue vascularity in radiation-induced fibrosis with optical coherence tomography

      Preclinical quantitative in-vivo assessment of skin tissue vascularity in radiation-induced fibrosis with optical coherence tomography

      Radiation therapy (RT) is widely and effectively used for cancer treatment but can also cause deleterious side effects, such as a late-toxicity complication called radiation-induced fibrosis (RIF). Accurate diagnosis of RIF requires analysis of histological sections to assess extracellular matrix infiltration. This is invasive, prone to sampling limitations, and thus rarely used; instead, current practice relies on subjective clinical surrogates, including visual observation, palpation, and patient symptomatology questionnaires. This preclinical study demonstrates that functional optical coherence tomography (OCT) is a useful tool for objective noninvasive in-vivo assessment and quantification of fibrosis-associated microvascular changes in tissue. Data were collected from murine ...

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    1-24 of 467 1 2 3 4 ... 18 19 20 »
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