1. 1-24 of 146 1 2 3 4 5 6 »
    1. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

      Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

      A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique ...

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    2. Real-time monitoring of hemodynamic changes in tumor vessels during photoimmunotherapy using optical coherence tomography

      Real-time monitoring of hemodynamic changes in tumor vessels during photoimmunotherapy using optical coherence tomography

      Photoimmunotherapy (PIT) is a cell-specific cancer therapy based on an armed antibody conjugate that induces rapid and highly selective cancer cell necrosis after exposure to near-infrared (NIR) light. The PIT treatment also induces the superenhanced permeability and retention effect, which allows high concentrations of nanoparticles to accumulate in the tumor bed. In our pilot studies, optical coherence tomography (OCT) reveals dramatic hemodynamic changes during PIT. We developed and applied speckle variance analysis, Doppler flow measurement, bulk motion removal, and automatic region of interest selection to quantify vessel diameter and blood velocity within tumors in vivo . OCT imaging reveals that blood ...

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    3. Accommodation-induced variations in retinal thickness measured by spectral domain optical coherence tomography

      Accommodation-induced variations in retinal thickness measured by spectral domain optical coherence tomography

      To research retinal stretching or distortion with accommodation, accommodation-induced changes in retinal thickness (RT) in the macular area were investigated in a population of young adults ( n = 23 ) by using a dual-channel spectral domain optical coherence tomography (SD-OCT) system manufactured in-house for this study. This dual-channel SD-OCT is capable of imaging the cornea and retina simultaneously with an imaging speed of 24 kHz A-line scan rate, which can provide the anatomical dimensions of the eye, including the RT and axial length. Thus, the modification of the RT with accommodation can be calculated. A significant decrease in the RT ( 13.50 ...

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    4. Visualization of the ocular pulse in the anterior chamber of the mouse eye in vivo using phase-sensitive optical coherence tomography

      Visualization of the ocular pulse in the anterior chamber of the mouse eye in vivo using phase-sensitive optical coherence tomography

      We report on a phase-based method for accurately measuring the ocular pulse in the anterior chamber in vivo . Using phase-sensitive optical coherence tomography with optimized scanning protocols and equations for compensating bulk motion and environmental vibrations, a high sensitivity of 0.9     μ m / s minimal velocity is demonstrated at a wide detection band of 0 to 380 Hz. The pulsatile relative motion between cornea and crystalline lens in rodents is visualized and quantified. The relative motion is most likely caused by respiration (1.6 Hz) and heartbeat (6.6 Hz). The velocity amplitude of the relative motion is 10.3 ...

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    5. Automated classification of optical coherence tomography images for the diagnosis of oral malignancy in the hamster cheek pouch

      Automated classification of optical coherence tomography images for the diagnosis of oral malignancy in the hamster cheek pouch

      Most studies evaluating the potential of optical coherence tomography (OCT) for the diagnosis of oral cancer are based on visual assessment of OCT B-scans by trained experts. Human interpretation of the large pool of data acquired by modern high-speed OCT systems, however, can be cumbersome and extremely time consuming. Development of image analysis methods for automated and quantitative OCT image analysis could therefore facilitate the evaluation of such a large volume of data. We report automated algorithms for quantifying structural features that are associated with the malignant transformation of the oral epithelium based on image processing of OCT data. The ...

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    6. User-guided segmentation for volumetric retinal optical coherence tomography images

      User-guided segmentation for volumetric retinal optical coherence tomography images

      Despite the existence of automatic segmentation techniques, trained graders still rely on manual segmentation to provide retinal layers and features from clinical optical coherence tomography (OCT) images for accurate measurements. To bridge the gap between this time-consuming need of manual segmentation and currently available automatic segmentation techniques, this paper proposes a user-guided segmentation method to perform the segmentation of retinal layers and features in OCT images. With this method, by interactively navigating three-dimensional (3-D) OCT images, the user first manually defines user-defined (or sketched) lines at regions where the retinal layers appear very irregular for which the automatic segmentation method ...

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    7. Histogram flow mapping with optical coherence tomography for in vivo skin angiography of hereditary hemorrhagic telangiectasia

      Histogram flow mapping with optical coherence tomography for in vivo skin angiography of hereditary hemorrhagic telangiectasia

      Speckle statistics of flowing scatterers have been well documented in the literature. Speckle variance optical coherence tomography exploits the large variance values of intensity changes in time caused mainly by the random backscattering of light resulting from translational activity of red blood cells to map out the microvascular networks. A method to map out the microvasculature malformation of skin based on the time-domain histograms of individual pixels is presented with results obtained from both normal skin and skin containing vascular malformation. Results demonstrated that this method can potentially map out deeper blood vessels and enhance the visualization of microvasculature in ...

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    8. Monitoring of interaction of low-frequency electric field with biological tissues upon optical clearing with optical coherence tomography

      Monitoring of interaction of low-frequency electric field with biological tissues upon optical clearing with optical coherence tomography

      The influence of a low-frequency electric field applied to soft biological tissues ex vivo at normal conditions and upon the topical application of optical clearing agents has been studied by optical coherence tomography (OCT). The electro-kinetic response of tissues has been observed and quantitatively evaluated by the double correlation OCT approach, utilizing consistent application of an adaptive Wiener filtering and Fourier domain correlation algorithm. The results show that fluctuations, induced by the electric field within the biological tissues are exponentially increased in time. We demonstrate that in comparison to impedance measurements and the mapping of the temperature profile at the ...

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    9. Characterizing the resolvability of real superluminescent diode sources for application to optical coherence tomography using a low coherence interferometry model

      Characterizing the resolvability of real superluminescent diode sources for application to optical coherence tomography using a low coherence interferometry model

      The axial resolution is a critical parameter in determining whether optical coherent tomography (OCT) can be used to resolve specific features in a sample image. Typically, measures of resolution have been attributed to the light source characteristics only, including the coherence length and the point spread function (PSF) width of the OCT light sources. The need to cost effectively visualize the generated PSF and OCT cross-correlated interferogram (A-scan) using many OCT light sources have led to the extrinsic evolution of the OCT simulation model presented. This research indicated that empirical resolution in vivo , as well as depending on the light ...

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    10. Optical coherence tomography today: speed, contrast, and multimodality

      Optical coherence tomography today: speed, contrast, and multimodality

      In the last 25 years, optical coherence tomography (OCT) has advanced to be one of the most innovative and most successful translational optical imaging techniques, achieving substantial economic impact as well as clinical acceptance. This is largely owing to the resolution improvements by a factor of 10 to the submicron regime and to the imaging speed increase by more than half a million times to more than 5 million A-scans per second, with the latter one accomplished by the state-of-the-art swept source laser technologies that are reviewed in this article. In addition, parallelization of OCT detection, such as line-field and ...

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    11. Three-dimensional optical coherence elastography by phase-sensitive comparison of C-scans

      Three-dimensional optical coherence elastography by phase-sensitive comparison of C-scans

      We present an acquisition method for optical coherence elastography (OCE) that enables acquisition of three-dimensional elastograms in 5 s, an order of magnitude faster than previously reported. In this method, based on compression elastography, the mechanical load applied to the sample is altered between acquisitions of consecutive optical coherence tomography volume scans (C-scans). The voxel-by-voxel phase difference between the volumes is used to determine the axial displacement and determining the gradient of the axial displacement versus depth gives the local axial strain. We demonstrate sub-100-microstrain sensitivity and high contrast in elastograms, acquired in 5 s, of structured phantoms and freshly ...

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    12. Special section guest editorial: selected topics in biophotonics: optical coherence tomography and biomolecular imaging with coherent Raman scattering microscopy

      Special section guest editorial: selected topics in biophotonics: optical coherence tomography and biomolecular imaging with coherent Raman scattering microscopy

      The Special Section on Selected Topics in Biophotonics: Optical Coherence Tomography and Biomolecular Imaging with Coherent Raman Scattering Microscopy comprises two invited review papers and several contributed papers from the summer school Biophotonics ’13, as well as contributed papers within this general scope.

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    13. Three-dimensional correction of conduction velocity in the embryonic heart using integrated optical mapping and optical coherence tomography

      Three-dimensional correction of conduction velocity in the embryonic heart using integrated optical mapping and optical coherence tomography

      Optical mapping (OM) of cardiac electrical activity conventionally collects information from a three-dimensional (3-D) surface as a two-dimensional (2-D) projection map. When applied to measurements of the embryonic heart, this method ignores the substantial and complex curvature of the heart surface, resulting in significant errors when calculating conduction velocity, an important electrophysiological parameter. Optical coherence tomography (OCT) is capable of imaging the 3-D structure of the embryonic heart and accurately characterizing the surface topology. We demonstrate an integrated OCT/OM imaging system capable of simultaneous conduction mapping and 3-D structural imaging. From these multimodal data, we obtained 3-D activation maps ...

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    14. Spiking cortical model-based nonlocal means method for speckle reduction in optical coherence tomography images

      Spiking cortical model-based nonlocal means method for speckle reduction in optical coherence tomography images

      Optical coherence tomography (OCT) images are usually degraded by significant speckle noise, which will strongly hamper their quantitative analysis. However, speckle noise reduction in OCT images is particularly challenging because of the difficulty in differentiating between noise and the information components of the speckle pattern. To address this problem, the spiking cortical model (SCM)-based nonlocal means method is presented. The proposed method explores self-similarities of OCT images based on rotation-invariant features of image patches extracted by SCM and then restores the speckled images by averaging the similar patches. This method can provide sufficient speckle reduction while preserving image details ...

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    15. Speckle reduction in optical coherence tomography images based on wave atoms

      Speckle reduction in optical coherence tomography images based on wave atoms

      Optical coherence tomography (OCT) is an emerging noninvasive imaging technique, which is based on low-coherence interferometry. OCT images suffer from speckle noise, which reduces image contrast. A shrinkage filter based on wave atoms transform is proposed for speckle reduction in OCT images. Wave atoms transform is a new multiscale geometric analysis tool that offers sparser expansion and better representation for images containing oscillatory patterns and textures than other traditional transforms, such as wavelet and curvelet transforms. Cycle spinning-based technology is introduced to avoid visual artifacts, such as Gibbs-like phenomenon, and to develop a translation invariant wave atoms denoising scheme. The ...

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    16. Optical coherence tomography microangiography for monitoring the response of vascular perfusion to external pressure on human skin tissue

      Optical coherence tomography microangiography for monitoring the response of vascular perfusion to external pressure on human skin tissue

      Characterization of the relationship between external pressure and blood flow is important in the examination of pressure-induced disturbance in tissue microcirculation. Optical coherence tomography (OCT)-based microangiography is a promising imaging technique, capable of providing the noninvasive extraction of functional vessels within the skin tissue with capillary-scale resolution. Here, we present a feasibility study of OCT microangiography (OMAG) to evaluate changes in blood perfusion in response to externally applied pressure on human skin tissue in vivo . External force is loaded normal to the tissue surface at the nailfold region of a healthy human volunteer. An incremental force is applied step ...

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    17. Robot-assisted three-dimensional registration for cochlear implant surgery using a common-path swept-source optical coherence tomography probe

      Robot-assisted three-dimensional registration for cochlear implant surgery using a common-path swept-source optical coherence tomography probe

      Cochlear implantation offers the potential to restore sensitive hearing in patients with severe to profound deafness. However, surgical placement of the electrode array within the cochlea can produce trauma to sensorineural components, particularly if the initial turn of the cochlea is not successfully navigated as the array is advanced. In this work, we present a robot-mounted common-path swept-source optical coherence tomography endoscopic platform for three-dimensional (3-D) optical coherence tomography (OCT) registration and preoperative surgical planning for cochlear implant surgery. The platform is composed of a common-path 600- μ m diameter fiber optic rotary probe attached to a five degrees of freedom ...

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    18. Evaluation of the marginal fit at implant–abutment interface by optical coherence tomography

      Evaluation of the marginal fit at implant–abutment interface by optical coherence tomography

      Vertical misfit of implant–abutment interface can affect the success of implant treatment; however, currently available modalities have limitations to detect these gaps. This study aimed to evaluate implant–abutment gaps in vitro using optical coherence tomography (OCT). Vertical misfit gaps sized 50, 100, 150, or 200 μ m were created between external hexagonal implants and titanium abutments (Nobel Biocare, Göteborg, Sweden). A porcine gingival tissue slice, 0.5, 1.0, 1.5, or 2.0 mm in thickness, was placed on each implant–abutment interface. The gaps were evaluated by swept-source OCT at a center wavelength of 1330 nm ...

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    19. Monitoring the blood coagulation process under various flow conditions with optical coherence tomography

      Monitoring the blood coagulation process under various flow conditions with optical coherence tomography

      Our previous work demonstrated that an optical coherence tomography (OCT) technique was able to characterize the whole blood coagulation process. The 1 / e light penetration depth ( d 1 / e ) derived from the profiles of reflectance versus depth was developed for detecting the whole blood coagulation process in static state. To consider the effect of blood flow, in the present study, d 1 / e versus time from the coagulating porcine blood circulated in a mock flow loop with various steady laminar flows at mean flow speed in the range from 5 to 25     mm / s . The variation of d 1 / e ...

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    20. Detection of breast surgical margins with optical coherence tomography imaging: a concept evaluation study

      Detection of breast surgical margins with optical coherence tomography imaging: a concept evaluation study

      This study aimed to evaluate the concept of using high-resolution optical coherence tomography (OCT) imaging to rapidly assess surgical specimens and determine if cancer positive margins were left behind in the surgical bed. A mouse model of breast cancer was used in this study. Surgical specimens from 30 animals were investigated with OCT and automated interpretation of the OCT images was performed and tested against histopathology findings. Specimens from 10 animals were used to build a training set of OCT images, while the remaining 20 specimens were used for a validation set of images. The validation study showed that automated ...

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    21. Full anterior segment biometry with extended imaging range spectral domain optical coherence tomography at 1340 nm

      Full anterior segment biometry with extended imaging range spectral domain optical coherence tomography at 1340 nm

      We demonstrate an extended-imaging-range anterior-segment optical coherence tomography (eAS-OCT) system for the biometric assessment of full AS in human eye. This newly developed eAS-OCT operating at 1340-nm wavelength band is simultaneously capable of an imaging speed of 120 kHz A-line scan rate, an axial resolution of 7.2 μ m, and an extended imaging range of up to 16 mm in air. Imaging results from three healthy subjects and one subject with a narrow-angle demonstrate the instrument’s utility. With this system, it can provide anatomical dimensions of AS, including central corneal thickness, anterior chamber width, anterior chamber depth, crystalline lens ...

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    22. Label-free cell-based assay with spectral-domain optical coherence phase microscopy

      Label-free cell-based assay with spectral-domain optical coherence phase microscopy

      Quantitative measurement of dynamic responses of unstained living cells is of great importance in many applications ranging from investigation of fundamental cellular functions to drug discoveries. Conventional optical methods for label-free cell-based assay examine cellular structural changes proximal to sensor surfaces under external stimuli, but require dedicated nanostructure-patterned substrates for operation. Here, we present a quantitative imaging method, spectral-domain optical coherence phase microscopy (SD-OCPM), as a viable optical platform for label-free cell-based assay. The instrument is based on a low-coherence interferometric microscope that enables quantitative depth-resolved phase measurement of a transparent specimen with high phase stability. We demonstrate SD-OCPM measurement ...

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    23. Parallelized multi–graphics processing unit framework for high-speed Gabor-domain optical coherence microscopy

      Parallelized multi–graphics processing unit framework for high-speed Gabor-domain optical coherence microscopy

      Gabor-domain optical coherence microscopy (GD-OCM) is a volumetric high-resolution technique capable of acquiring three-dimensional (3-D) skin images with histological resolution. Real-time image processing is needed to enable GD-OCM imaging in a clinical setting. We present a parallelized and scalable multi-graphics processing unit (GPU) computing framework for real-time GD-OCM image processing. A parallelized control mechanism was developed to individually assign computation tasks to each of the GPUs. For each GPU, the optimal number of amplitude-scans (A-scans) to be processed in parallel was selected to maximize GPU memory usage and core throughput. We investigated five computing architectures for computational speed-up in processing ...

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    24. Nondestructive observation of teeth post core space using optical coherence tomography: a pilot study

      Nondestructive observation of teeth post core space using optical coherence tomography: a pilot study

      Coronal tooth lesions, such as caries, enamel cracking, and composite resin restoration cavities, have been observed by optical coherence tomography (OCT). This pilot study was performed to verify whether OCT could reveal details of root canals filled with resin core build-up. A dual-cure, one-step, self-etch adhesive system-bonding agent (Clearfil Bond SE ONE, Kuraray Noritake Dental) and dual-cure resin composite core material (Clearfil DC Core Automix ONE, Kuraray Noritake Dental) were used according to the manufacturer’s instructions in root canals. OCT was performed at three stages of the core build-up: after the post space preparation, after bonding application, and after ...

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      Mentions: Osaka University
    1-24 of 146 1 2 3 4 5 6 »
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