1. 1-24 of 521 1 2 3 4 ... 20 21 22 »
    1. Feasibility of combined optical coherence tomography and autofluorescence imaging for visualization of needle biopsy placement

      Feasibility of combined optical coherence tomography and autofluorescence imaging for visualization of needle biopsy placement

      Significance: Diagnosis of suspicious lung nodules requires precise collection of relevant biopsies for histopathological analysis. Using optical coherence tomography and autofluorescence imaging (OCT-AFI) to improve diagnostic yield in parts of the lung inaccessible to larger imaging methods may allow for reducing complications related to the alternative of computed tomography-guided biopsy. Aim: Feasibility of OCT-AFI combined with a commercially available lung biopsy needle was demonstrated for visualization of needle puncture sites in airways with diameters as small as 1.9 mm. Approach: A miniaturized OCT-AFI imaging stylet was developed to be inserted through an 18G biopsy needle. We present design considerations ...

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    2. Dual-modality optical coherence tomography and frequency-domain fluorescence lifetime imaging microscope system for intravascular imaging

      Dual-modality optical coherence tomography and frequency-domain fluorescence lifetime imaging microscope system for intravascular imaging

      Significance: Detailed biochemical and morphological imaging of the plaque burdened coronary arteries holds the promise of improved understanding of atherosclerosis plaque development, ultimately leading to better diagnostics and therapies. Aim: Development of a dual-modality intravascular catheter supporting swept-source optical coherence tomography (OCT) and frequency-domain fluorescence lifetime imaging (FD-FLIM) of endogenous fluorophores with UV excitation. Approach: We instituted a refined approach to endoscope development that combines simulation in a commercial ray tracing program, fabrication, and a measurement method for optimizing ball-lens performance. With this approach, we designed and developed a dual-modality catheter endoscope based on a double-clad fiber supporting OCT through ...

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    3. Optical microangiography reveals temporal and depth-resolved hemodynamic change in mouse barrel cortex during whisker stimulation

      Optical microangiography reveals temporal and depth-resolved hemodynamic change in mouse barrel cortex during whisker stimulation

      Significance: Cerebral blood flow (CBF) regulation at neurovascular coupling (NVC) plays an important role in normal brain functioning to support oxygen delivery to activating neurons. Therefore, studying the mechanisms of CBF adjustment is crucial for the improved understanding of brain activity. Aim: We investigated the temporal profile of hemodynamic signal change in mouse cortex caused by neural activation and its variation over cortical depth. Approach: Following the cranial window surgery, intrinsic optical signal imaging (IOSI) was used to spatially locate the activated region in mouse cortex during whisker stimulation. Optical microangiography (OMAG), the functional extension of optical coherence tomography, was ...

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    4. Automatic diagnosis of macular diseases from OCT volume based on its two-dimensional feature map and convolutional neural network with attention mechanism.

      Automatic diagnosis of macular diseases from OCT volume based on its two-dimensional feature map and convolutional neural network with attention mechanism.

      Significance: Automatic and accurate classification of three-dimensional (3-D) retinal optical coherence tomography (OCT) images is essential for assisting ophthalmologist in the diagnosis and grading of macular diseases. Therefore, more effective OCT volume classification for automatic recognition of macular diseases is needed. Aim: For OCT volumes in which only OCT volume-level labels are known, OCT volume classifiers based on its global feature and deep learning are designed, validated, and compared with other methods. Approach: We present a general framework to classify OCT volume for automatic recognizing macular diseases. The architecture of the framework consists of three modules: B-scan feature extractor, two-dimensional ...

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    5. Detection of localized pulsatile motion in cutaneous microcirculation by speckle decorrelation optical coherence tomography angiography

      Detection of localized pulsatile motion in cutaneous microcirculation by speckle decorrelation optical coherence tomography angiography

      Significance: Pulsatility is a vital characteristic of the cardiovascular system. Characterization of the pulsatility pattern locally in the peripheral microvasculature is currently not readily available and would provide an additional source of information, which may prove important in understanding the pathophysiology of arterial stiffening, vascular ageing, and their linkage with cardiovascular disease development. Aim: We aim to confirm the suitability of speckle decorrelation optical coherence tomography angiography (OCTA) under various noncontact/contact scanning protocols for the visualization of pulsatility patterns in vessel-free tissue and in the microvasculature of peripheral human skin. Results: Results from five healthy subjects show distinct pulsatile ...

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    6. Water wavenumber calibration for visible light optical coherence tomography

      Water wavenumber calibration for visible light optical coherence tomography

      Significance : Visible light optical coherence tomography (OCT) is emerging for spectroscopic and ultrahigh resolution imaging, but challenges remain. Depth-dependent dispersion limits retinal image quality and current correction approaches are cumbersome. Inconsistent group refractive indices during image reconstruction also limit reproducibility. Aim: To introduce and evaluate water wavenumber calibration (WWC), which corrects depth-dependent dispersion and provides an accurate depth axis in water. Approach: Enabled by a visible light OCT spectrometer configuration with a 3- to 4-dB sensitivity roll-off over 1 mm in air across a 90-nm bandwidth, we determine the spectral phase of a 1-mm water cell, an affine function of ...

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    7. High-speed optical coherence tomography angiography for the measurement of stimulus-induced retrograde vasodilation of cerebral pial arteries in awake mice

      High-speed optical coherence tomography angiography for the measurement of stimulus-induced retrograde vasodilation of cerebral pial arteries in awake mice

      Significance: Having a clear understanding of functional hyperemia is crucial for functional brain imaging and neurological disease research. Vasodilation induced by sensory stimulus propagates from the arterioles to the upstream pial arteries in a retrograde fashion. As retrograde vasodilation occurs briefly in the early stage of functional hyperemia, an imaging technique with a high temporal resolution is required for its measurement. Aim: We aimed to present an imaging method to measure stimulus-induced retrograde vasodilation in awake animals. Approach: An imaging method based on optical coherence tomography angiography, which enables a high-speed and label-free vessel diameter measurement, was developed and applied ...

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    8. Influence of tissue fixation on depth-resolved birefringence of oral cavity tissue samples

      Influence of tissue fixation on depth-resolved birefringence of oral cavity tissue samples

      Significance: To advance our understanding of the contrast observed when imaging with polarization-sensitive optical coherence tomography (PS-OCT) and its correlation with oral cancerous pathologies, a detailed comparison with histology provided via ex vivo fixed tissue is required. The effects of tissue fixation, however, on such polarization-based contrast have not yet been investigated. Aim: A study was performed to assess the impact of tissue fixation on depth-resolved (i.e., local) birefringence measured with PS-OCT. Approach: A PS-OCT system based on depth-encoded polarization multiplexing and polarization-diverse detection was used to measure the Jones matrix of a sample. A wide variety of ex ...

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    9. Ex-vivo Alzheimer’s disease brain tissue investigation: a multiscale approach using 1060-nm swept source optical coherence tomography for a direct correlation to histology

      Ex-vivo Alzheimer’s disease brain tissue investigation: a multiscale approach using 1060-nm swept source optical coherence tomography for a direct correlation to histology

      Significance: Amyloid-beta (A-β) plaques are pathological protein deposits formed in the brain of Alzheimer’s disease (AD) patients upon disease progression. Further research is needed to elucidate the complex underlying mechanisms involved in their formation using label-free, tissue preserving, and volumetric techniques. Aim: The aim is to achieve a one-to-one correlation of optical coherence tomography (OCT) data to histological micrographs of brain tissue using 1060-nm swept source OCT. Approach: A-β plaques were investigated in ex-vivo AD brain tissue using OCT with the capability of switching between two magnifications. For the exact correlation to histology, a 3D-printed tool was designed to ...

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    10. Study on the structure and optical imaging characteristics of an all-fiber OCT probe

      Study on the structure and optical imaging characteristics of an all-fiber OCT probe

      Aiming at small size, compact structure, strong light-collecting ability, and low loss requirements of optical coherence tomography (OCT) probes used for human body detection, we design an all-fiber OCT probe, which is composed of a single-mode fiber and a multimode fiber (MMF) with spherical lens. By measuring the optical performance of these probes, we found that, when the length of the MMF of the composite probe is 372  μm and the diameter of the ball lens is 300  μm, it has the strongest focusing effect and a large reflected light signal receiving angle. Furthermore, the OCT probe studied was applied ...

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    11. Live mechanistic assessment of localized cardiac pumping in mammalian tubular embryonic heart

      Live mechanistic assessment of localized cardiac pumping in mammalian tubular embryonic heart

      Significance: Understanding how the valveless embryonic heart pumps blood is essential to elucidate biomechanical cues regulating cardiogenesis, which is important for the advancement of congenital heart defects research. However, methods capable of embryonic cardiac pumping analysis remain limited, and assessing this highly dynamic process in mammalian embryos is challenging. New approaches are critically needed to address this hurdle. Aim: We report an imaging-based approach for functional assessment of localized pumping dynamics in the early tubular embryonic mouse heart. Approach: Four-dimensional optical coherence tomography was used to obtain structural and Doppler hemodynamic imaging of the beating heart in live mouse embryos ...

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    12. Measurement of optic axis orientation with single-mode fiber-based polarization-sensitive optical coherence tomography

      Measurement of optic axis orientation with single-mode fiber-based polarization-sensitive optical coherence tomography

      An algorithm is presented that can be used to obtain accurate optic axis orientation of birefringent tissue samples. A single-mode fiber (SMF)-based polarization-sensitive optical coherence tomography with a single linearly polarized incident light was used in the measurements in which the light reflected from the sample and detected by the spectrometer is linearly polarized light at 45 deg with respect to the experimental horizontal axis. By employing polarization controllers to completely specify the parameters of the fiber system, the absolute optic axis orientation could then be estimated accurately by analyzing the Mueller matrices of the fiber system and sample ...

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    13. Intracardiac radiofrequency ablation in living swine guided by polarization-sensitive optical coherence tomography

      Intracardiac radiofrequency ablation in living swine guided by polarization-sensitive optical coherence tomography

      Significance: Pulmonary vein isolation with catheter-based radiofrequency ablation (RFA) is carried out frequently to treat atrial fibrillation. However, RFA lesion creation is only guided by indirect information (e.g., temperature, impedance, and contact force), which may result in poor lesion quality (e.g., nontransmural) and can lead to reoccurrence or complications. Aim: The feasibility of guiding intracardiac RFA with an integrated polarization-sensitive optical coherence tomography (PSOCT)-RFA catheter in the right atria (RA) of living swine is demonstrated. Approach : In total, 12 sparse lesions were created in the RA of three living swine using an integrated PSOCT-RFA catheter with standard ...

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    14. Heartbeat OCE: corneal biomechanical response to simulated heartbeat pulsation measured by optical coherence elastography

      Heartbeat OCE: corneal biomechanical response to simulated heartbeat pulsation measured by optical coherence elastography

      Significance: It is generally agreed that the corneal mechanical properties are strongly linked to many eye diseases and could be used to assess disease progression and response to therapies. Elastography is the most notable method of assessing corneal mechanical properties, but it generally requires some type of external excitation to induce a measurable displacement in the tissue. Aim: We present Heartbeat Optical Coherence Elastography (Hb-OCE), a truly passive method that can measure the elasticity of the cornea based on intrinsic corneal displacements induced by the heartbeat. Approach: Hb-OCE measurements were performed in untreated and UV-A/riboflavin cross-linked porcine corneas ex ...

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    15. Low-cost, ultracompact handheld optical coherence tomography probe for in vivo oral maxillofacial tissue imaging

      Low-cost, ultracompact handheld optical coherence tomography probe for in vivo oral maxillofacial tissue imaging

      Significance: Optical coherence tomography (OCT) has proven useful for detecting various oral maxillofacial abnormalities. To apply it to clinical applications including biopsy guidance and routine screening, a handheld imaging probe is indispensable. OCT probes reported for oral maxillofacial imaging were either based on a bulky galvanometric mirror pair (not compact or long enough) or a distal-end microelectromechanical systems (MEMS) scanner (raised safety concerns), or adapted from fiber-optic catheters (ill-suited for oral cavity geometry). Aim: To develop a handheld probe featuring great compactness and excellent maneuverability for oral maxillofacial tissue imaging. Approach: A dual-axis MEMS scanner was deployed at the proximal ...

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    16. Parametric imaging of attenuation by optical coherence tomography: review of models, methods, and clinical translation

      Parametric imaging of attenuation by optical coherence tomography: review of models, methods, and clinical translation

      Significance: Optical coherence tomography (OCT) provides cross-sectional and volumetric images of backscattering from biological tissue that reveal the tissue morphology. The strength of the scattering, characterized by an attenuation coefficient, represents an alternative and complementary tissue optical property, which can be characterized by parametric imaging of the OCT attenuation coefficient. Over the last 15 years, a multitude of studies have been reported seeking to advance methods to determine the OCT attenuation coefficient and developing them toward clinical applications. Aim: Our review provides an overview of the main models and methods, their assumptions and applicability, together with a survey of preclinical ...

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    17. Longitudinal optical coherence tomography imaging of tissue repair and microvasculature regeneration and function after targeted cerebral ischemia

      Longitudinal optical coherence tomography imaging of tissue repair and microvasculature regeneration and function after targeted cerebral ischemia

      Significance: Understanding how the brain recovers from cerebral tissue and vascular damage after an ischemic event can help develop new therapeutic strategies for the treatment of stroke. Aim: We investigated cerebral tissue repair and microvasculature regeneration and function after a targeted ischemic stroke. Approach: Following photothrombosis occlusion of microvasculature, chronic optical coherence tomography (OCT)-based angiography was used to track ischemic tissue repair and microvasculature regeneration at three different cortical depths and up to 28 days in awake animals. Capillary network orientation analysis was performed to study the structural pattern of newly formed microvasculature. Based on the time-resolved OCT-angiography, we ...

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    18. INS-fOCT: a label-free, all-optical method for simultaneously manipulating and mapping brain function

      INS-fOCT: a label-free, all-optical method for simultaneously manipulating and mapping brain function

      Significance: Current approaches to stimulating and recording from the brain have combined electrical or optogenetic stimulation with recording approaches, such as two-photon, electrophysiology (EP), and optical intrinsic signal imaging (OISI). However, we lack a label-free, all-optical approach with high spatial and temporal resolution. Aim: To develop a label-free, all-optical method that simultaneously manipulates and images brain function using pulsed near-infrared light (INS) and functional optical coherence tomography (fOCT), respectively. Approach: We built a coregistered INS, fOCT, and OISI system. OISI and EP recordings were employed to validate the fOCT signals. Results: The fOCT signal was reliable and regional, and the ...

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    19. Laser-induced elastic wave classification: thermoelastic versus ablative regimes for all-optical elastography applications

      Laser-induced elastic wave classification: thermoelastic versus ablative regimes for all-optical elastography applications

      Significance : Shear wave optical coherence elastography is an emerging technique for characterizing tissue biomechanics that relies on the generation of elastic waves to obtain the mechanical contrast. Various techniques, such as contact, acoustic, and pneumatic methods, have been used to induce elastic waves. However, the lack of higher-frequency components within the elastic wave restricts their use in thin samples. The methods also require moving parts and/or tubing, which therefore limits the extent to which they can be miniaturized. Aim : To overcome these limitations, we propose an all-optical approach using photothermal excitation. Depending on the absorption coefficient of the sample ...

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    20. Achieving the ideal point spread in swept source OCT

      Achieving the ideal point spread in swept source OCT

      Side lobe artifacts on point spread functions can be traced back to (1) fringe visibility variation across the spectrum, (2) errors in sampling instances, and (3) window functions. We demonstrate signal processing methods for correcting for all three of these issues. These methods require a system calibration step. If the systems slowly age, the recalibration step could be performed in the field with a fixtured target.

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    21. Selective retina therapy monitoring by speckle variance optical coherence tomography for dosimetry control

      Selective retina therapy monitoring by speckle variance optical coherence tomography for dosimetry control

      Significance: Selective retina therapy (SRT) selectively targets the retinal pigment epithelium (RPE) and reduces negative side effects by avoiding thermal damages of the adjacent photoreceptors, the neural retina, and the choroid. However, the selection of proper laser energy for the SRT is challenging because of ophthalmoscopically invisible lesions in the RPE and different melanin concentrations among patients or even regions within an eye. Aim: We propose and demonstrate SRT monitoring based on speckle variance optical coherence tomography (svOCT) for dosimetry control. Approach: M-scans, time-resolved sequence of A-scans, of ex vivo bovine retina irradiated by 1.7-μs duration laser pulses ...

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    22. Dimensional characterization of large opaque samples and microdeformations by low coherence interferometry

      Dimensional characterization of large opaque samples and microdeformations by low coherence interferometry

      We report on the application of an interferometric system based on the low-coherence interferometry technique to the dimensional characterization of large opaque mechanical parts as well as microdeformations experienced by them. The implemented scheme is capable of simultaneously measuring very small deformations and relatively large dimensions or thicknesses (several centimeters) of the sample. By applying the chirp Fourier transform algorithm, it was possible to measure changes in thickness with an uncertainty of 0.35  μm when a 7-cm-thick sample was measured. The measurement scheme was implemented in optical fiber, which makes it highly adaptable to industrial conditions. It employs a ...

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    23. In vivo brain imaging with multimodal optical coherence microscopy in a mouse model of thromboembolic photochemical stroke

      In vivo brain imaging with multimodal optical coherence microscopy in a mouse model of thromboembolic photochemical stroke

      We used a new multimodal imaging system that combines optical coherence microscopy and brightfield microscopy. Using this in vivo brain monitoring approach and cranial window implantation, we three-dimensionally visualized the vascular network during thrombosis, with high temporal (18 s) and spatial (axial, 2.5  μm; lateral, 2.2  μm) resolution. We used a modified mouse model of photochemical thromboembolic stroke in order to more accurately parallel human stroke. Specifically, we applied green laser illumination to focally occlude a branch of the middle cerebral artery. Despite the recanalization of the superficial arteries at 24 h after stroke, no blood flow was ...

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    24. Utility of endoscopic anatomical optical coherence tomography in functional rhinoplasty

      Utility of endoscopic anatomical optical coherence tomography in functional rhinoplasty

      Objective measurement of the nasal valve region is valuable for the assessment of functional rhinoplasty surgical outcomes. Anatomical optical coherence tomography (aOCT) is an imaging modality that may be used to obtain real-time, quantitative, and volumetric scans of the nasal airway. We aim to evaluate if volumetric aOCT imaging is useful for the examination of the nasal valve region before and after functional rhinoplasty procedures. aOCT scans of the nasal valves were performed on four cadaveric heads before and after spreader graft and butterfly graft procedures. The resulting aOCT images were compared against video endoscopy images, and the segmented volumes ...

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      Mentions: Amy L. Oldenburg
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