1. 1-24 of 285 1 2 3 4 ... 10 11 12 »
    1. Automatic motion correction for in vivo human skin optical coherence tomography angiography through combined rigid and nonrigid registration

      Automatic motion correction for in vivo human skin optical coherence tomography angiography through combined rigid and nonrigid registration

      When using optical coherence tomography angiography (OCTA), the development of artifacts due to involuntary movements can severely compromise the visualization and subsequent quantitation of tissue microvasculatures. To correct such an occurrence, we propose a motion compensation method to eliminate artifacts from human skin OCTA by means of step-by-step rigid affine registration, rigid subpixel registration, and nonrigid B-spline registration. To accommodate this remedial process, OCTA is conducted using two matching all-depth volume scans. Affine transformation is first performed on the large vessels of the deep reticular dermis, and then the resulting affine parameters are applied to all-depth vasculatures with a further ...

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    2. Optical coherence tomography angiography-based capillary velocimetry

      Optical coherence tomography angiography-based capillary velocimetry

      Challenge persists in the field of optical coherence tomography (OCT) when it is required to quantify capillary blood flow within tissue beds in vivo . We propose a useful approach to statistically estimate the mean capillary flow velocity using a model-based statistical method of eigendecomposition (ED) analysis of the complex OCT signals obtained with the OCT angiography (OCTA) scanning protocol. ED-based analysis is achieved by the covariance matrix of the ensemble complex OCT signals, upon which the eigenvalues and eigenvectors that represent the subsets of the signal makeup are calculated. From this analysis, the signals due to moving particles can be ...

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    3. Automated circumferential construction of first-order aqueous humor outflow pathways using spectral-domain optical coherence tomography

      Automated circumferential construction of first-order aqueous humor outflow pathways using spectral-domain optical coherence tomography

      The purpose was to create a three-dimensional (3-D) model of circumferential aqueous humor outflow (AHO) in a living human eye with an automated detection algorithm for Schlemm’s canal (SC) and first-order collector channels (CC) applied to spectral-domain optical coherence tomography (SD-OCT). Anterior segment SD-OCT scans from a subject were acquired circumferentially around the limbus. A Bayesian Ridge method was used to approximate the location of the SC on infrared confocal laser scanning ophthalmoscopic images with a cross multiplication tool developed to initiate SC/CC detection automated through a fuzzy hidden Markov Chain approach. Automatic segmentation of SC and initial ...

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    4. En-face time-domain optical coherence tomography with dynamic focus for high-resolution imaging

      En-face time-domain optical coherence tomography with dynamic focus for high-resolution imaging

      Optical coherence tomography (OCT) is capable of imaging microstructures within translucid samples. A time-domain version of the OCT technology is employed here due to its compatibility with the dynamic focus (DF) procedure. DF means moving the confocal gate in synchronism with the depth scanning via the coherence gate. A DF-OCT setup was implemented for imaging samples at 1300 nm. Its confocal gate of 180    μ m 180  μm allows the achievement of good and similar transversal resolution along its much larger axial range. Images of a phantom, human skin, teeth, and larynx with and without DF are demonstrated.

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    5. Colposcopic imaging using visible-light optical coherence tomography

      Colposcopic imaging using visible-light optical coherence tomography

      High-resolution colposcopic optical coherence tomography (OCT) provides key anatomical measures, such as thickness and minor traumatic injury of vaginal epithelium, of the female reproductive tract noninvasively. This information can be helpful in both fundamental investigations in animal models and disease screenings in humans. We present a fiber-based visible-light OCT and two probe designs for colposcopic application. One probe conducts circular scanning using a DC motor, and the other probe is capable of three-dimensional imaging over a 4.6 × 4.6 - mm 2 4.6×4.6-mm2 area using a pair of galvo scanners. Using this colposcopic vis-OCT with both probes ...

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    6. Comparative study of shear wave-based elastography techniques in optical coherence tomography

      Comparative study of shear wave-based elastography techniques in optical coherence tomography

      We compare five optical coherence elastography techniques able to estimate the shear speed of waves generated by one and two sources of excitation. The first two techniques make use of one piezoelectric actuator in order to produce a continuous shear wave propagation or a tone-burst propagation (TBP) of 400 Hz over a gelatin tissue-mimicking phantom. The remaining techniques utilize a second actuator located on the opposite side of the region of interest in order to create three types of interference patterns: crawling waves, swept crawling waves, and standing waves, depending on the selection of the frequency difference between the two ...

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    7. Robust phase unwrapping for phase images in Fourier domain Doppler optical coherence tomography

      Robust phase unwrapping for phase images in Fourier domain Doppler optical coherence tomography

      To solve the 2 π 2π phase ambiguity for phase-resolved Doppler images in Doppler optical coherence tomography, we present a modified network programming technique for the first time to the best of our knowledge. The proposed method assumes that error of the discrete derivatives between unwrapped phase image and wrapped phase image can be arbitrary values instead of integer-multiple of 2 π 2π , which makes the real-phase restoration accurate and robust against noise. We compared our proposed method with the network programming method. Parameters including root-mean-square-error and noise amplification degree were adopted for comparison. The experimental study on simulated images, phantom, and ...

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      Mentions: Yong Huang
    8. Strip-based registration of serially acquired optical coherence tomography angiography

      Strip-based registration of serially acquired optical coherence tomography angiography

      The visibility of retinal microvasculature in optical coherence tomography angiography (OCT-A) images is negatively affected by the small dimension of the capillaries, pulsatile blood flow, and motion artifacts. Serial acquisition and time-averaging of multiple OCT-A images can enhance the definition of the capillaries and result in repeatable and consistent visualization. We demonstrate an automated method for registration and averaging of serially acquired OCT-A images. Ten OCT-A volumes from six normal control subjects were acquired using our prototype 1060-nm swept source OCT system. The volumes were divided into microsaccade-free en face angiogram strips, which were affine registered using scale-invariant feature transform ...

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    9. Segmentation of nucleus and cytoplasm of a single cell in three-dimensional tomogram using optical coherence tomography

      Segmentation of nucleus and cytoplasm of a single cell in three-dimensional tomogram using optical coherence tomography

      A random rayburst sampling (RRBS) framework was developed to detect the nucleus and cell membrane boundaries in three-dimensional (3-D) space. Raw images were acquired through a full-field optical coherence tomography system with submicron resolution—i.e., 0.8    μ m 0.8  μm in lateral and 0.9    μ m 0.9  μm in axial directions. The near-isometric resolution enables 3-D segmentation of a nucleus and cell membrane for determining the volumetric nuclear-to-cytoplasmic (N/C) ratio of a single cell. The RRBS framework was insensitive to the selection of seeds and image pixel noise. The robustness of the RRBS framework was verified ...

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    10. Quantitative characterization of mechanically indented in vivo human skin in adults and infants using optical coherence tomography

      Quantitative characterization of mechanically indented in vivo human skin in adults and infants using optical coherence tomography

      Influenced by both the intrinsic viscoelasticity of the tissue constituents and the time-evolved redistribution of fluid within the tissue, the biomechanical response of skin can reflect not only localized pathology but also systemic physiology of an individual. While clinical diagnosis of skin pathologies typically relies on visual inspection and manual palpation, a more objective and quantitative approach for tissue characterization is highly desirable. Optical coherence tomography (OCT) is an interferometry-based imaging modality that enables in vivo assessment of cross-sectional tissue morphology with micron-scale resolution, which surpasses those of most standard clinical imaging tools, such as ultrasound imaging and magnetic resonance ...

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    11. Applanation optical coherence elastography: noncontact measurement of intraocular pressure, corneal biomechanical properties, and corneal geometry with a single instrument

      Applanation optical coherence elastography: noncontact measurement of intraocular pressure, corneal biomechanical properties, and corneal geometry with a single instrument

      Current clinical tools provide critical information about ocular health such as intraocular pressure (IOP). However, they lack the ability to quantify tissue material properties, which are potent markers for ocular tissue health and integrity. We describe a single instrument to measure the eye-globe IOP, quantify corneal biomechanical properties, and measure corneal geometry with a technique termed applanation optical coherence elastography (Appl-OCE). An ultrafast OCT system enabled visualization of corneal dynamics during noncontact applanation tonometry and direct measurement of micro air-pulse induced elastic wave propagation. Our preliminary results show that the proposed Appl-OCE system can be used to quantify IOP, corneal ...

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    12. Optical coherence tomography with a 2.8-mm beam diameter and sensorless defocus and astigmatism correction

      Optical coherence tomography with a 2.8-mm beam diameter and sensorless defocus and astigmatism correction

      An optical coherence tomography (OCT) system with a 2.8-mm beam diameter is presented. Sensorless defocus correction can be performed with a Badal optometer and astigmatism correction with a liquid crystal device. OCT B-scans were used in an image-based optimization algorithm for aberration correction. Defocus can be corrected from − 4.3    D −4.3  D to + 4.3    D +4.3  D and vertical and oblique astigmatism from − 2.5    D −2.5  D to + 2.5    D +2.5  D . A contrast gain of 6.9 times was measured after aberration correction. In comparison with a 1.3-mm beam ...

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      Mentions: Barry Cense
    13. Dynamic multimodal full-field optical coherence tomography and fluorescence structured illumination microscopy

      Dynamic multimodal full-field optical coherence tomography and fluorescence structured illumination microscopy

      We report on the development of a configuration of a multimodal full-field optical coherence tomography (FF-OCT) and fluorescence microscope. Our system can simultaneously acquire FF-OCT and structured illumination microscopy images. Dynamic parallel evolution of tissue microstructures and biochemical environments can be visualized. We use high numerical aperture objectives to optimize the combination of the two modalities. We imaged the propagation of mechanical waves initiated by calcium waves in a heart wall to illustrate the interest of simultaneous recording of mechanical and biochemical information.

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    14. Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 2: implementation

      Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 2: implementation

      We introduce a theoretical method for simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography (FD-OCT) without any auxiliary arrangement. The input data to the formalism are the FD-OCT measured optical path lengths (OPLs) and properly selected spectral components of FD-OCT interference spectrum. The outputs of the formalism can be affected significantly by uncertainty in measuring the OPLs. An optimization method is introduced to deal with the relatively large amount of uncertainty in measured OPLs and enhance the final results. Simulation result shows that by using the optimization method, indices can be extracted ...

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    15. Automated three-dimensional registration and volume rebuilding for wide-field angiographic and structural optical coherence tomography

      Automated three-dimensional registration and volume rebuilding for wide-field angiographic and structural optical coherence tomography

      We propose a three-dimensional (3-D) registration method to correct motion artifacts and construct the volume structure for angiographic and structural optical coherence tomography (OCT). This algorithm is particularly suitable for the nonorthogonal wide-field OCT scan acquired by a ultrahigh-speed swept-source system ( > 200    kHz >200  kHz A-scan rate). First, the transverse motion artifacts are corrected by the between-frame registration based on en face OCT angiography (OCTA). After A-scan transverse translation between B-frames, the axial motions are corrected based on the rebuilt boundary of inner limiting membrane. Finally, a within-frame registration is performed for local optimization based on cross-sectional OCTA. We evaluated ...

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    16. Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 1: theory

      Simultaneous measurement of refractive index and thickness of multilayer systems using Fourier domain optical coherence tomography, part 1: theory

      We introduce a theoretical framework for simultaneous refractive index and thickness measurement of multilayer systems using the Fourier domain optical coherence tomography (FD-OCT) system without any previous information about the item under investigation. The input data to the new formalism are the FD-OCT measured optical path lengths and properly selected spectral components of the FD-OCT interference spectrum. No additional arrangement, reference reflector, or mechanical scanning is needed in this approach. Simulation results show that the accuracy of the extracted parameters depends on the index contrast of the sample while it is insensitive to the sample’s thickness profile. For transparent ...

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    17. Impact of temporal resolution on estimating capillary RBC-flux with optical coherence tomography

      Impact of temporal resolution on estimating capillary RBC-flux with optical coherence tomography

       Optical coherence tomography (OCT) has been used to measure capillary red blood cell (RBC) flux. However, one important technical issue is that the accuracy of this method is subject to the temporal resolution (ΔtΔt) of the repeated RBC-passage B-scans. A ceiling effect arises due to an insufficient ΔtΔt limiting the maximum RBC-flux that can be measured. In this letter, we first present simulations demonstrating that Δt=1.5  msΔt=1.5  mspermits measuring RBC-flux up to 150  RBCs/s150  RBCs/s with an underestimation of 9%. The simulations further show that measurements with Δt=3 ...

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    18. Detection of cervical intraepithelial neoplasia by using optical coherence tomography in combination with microscopy

      Detection of cervical intraepithelial neoplasia by using optical coherence tomography in combination with microscopy

      Optical coherence tomography (OCT) is a noninvasive high-resolution imaging technique that permits the detection of cancerous and precancerous lesions of the uterine cervix. The purpose of this study was to evaluate a new system that integrates an OCT device into a microscope. OCT images were taken from loop electrosurgical excision procedure (LEEP) specimens under microscopic guidance. The images were blinded with respect to their origin within the microscopic image and analyzed independently by two investigators using initially defined criteria and later compared to the corresponding histology. Sensitivity and specificity were calculated with respect to the correct identification of high-grade squamous ...

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    19. Fully automated macular pathology detection in retina optical coherence tomography images using sparse coding and dictionary learning

      Fully automated macular pathology detection in retina optical coherence tomography images using sparse coding and dictionary learning

      We propose a framework for automated detection of dry age-related macular degeneration (AMD) and diabetic macular edema (DME) from retina optical coherence tomography (OCT) images, based on sparse coding and dictionary learning. The study aims to improve the classification performance of state-of-the-art methods. First, our method presents a general approach to automatically align and crop retina regions; then it obtains global representations of images by using sparse coding and a spatial pyramid; finally, a multiclass linear support vector machine classifier is employed for classification. We apply two datasets for validating our algorithm: Duke spectral domain OCT (SD-OCT) dataset, consisting of ...

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    20. Optical coherence tomography-based topography determination of corneal grafts in eye bank cultivation

      Optical coherence tomography-based topography determination of corneal grafts in eye bank cultivation

      Vision loss due to corneal injuries or diseases can be treated by transplantation of human corneal grafts (keratoplasty). However, quality assurance in retrieving and cultivating the tissue transplants is confined to visual and microbiological testing. To identify previous refractive surgery or morphological alterations, an automatic, noncontact, sterile screening procedure is required. Twenty-three corneal grafts have been measured in organ culture with a clinical spectral-domain optical coherence tomographer. Employing a biconic surface fit with 10 degrees of freedom, the radii of curvature and conic constants could be estimated for the anterior and posterior corneal surfaces. Thereupon, central corneal thickness, refractive values ...

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    21. Optical sensing method to analyze germination rate of Capsicum annum seeds treated with growth-promoting chemical compounds using optical coherence tomography

      Optical sensing method to analyze germination rate of Capsicum annum seeds treated with growth-promoting chemical compounds using optical coherence tomography

      Seed germination rate differs based on chemical treatments, and nondestructive measurements of germination rate have become an essential requirement in the field of agriculture. Seed scientists and other biologists are interested in optical sensing technologies-based biological discoveries due to nondestructive detection capability. Optical coherence tomography (OCT) has recently emerged as a powerful method for biological and plant material discoveries. We report an extended application of OCT by monitoring the germination rate acceleration of chemically primed seeds. To validate the versatility of the method, Capsicum annum seeds were primed using three chemical compounds: sterile distilled water (SDW), butandiol, and 1-hexadecene. Monitoring ...

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    22. In vivo three-dimensional imaging of human corneal nerves using Fourier-domain optical coherence tomography

      In vivo three-dimensional imaging of human corneal nerves using Fourier-domain optical coherence tomography

      We have employed Fourier-domain optical coherence tomography (FD-OCT) to achieve corneal nerve imaging, which could be useful in surgical planning and refractive surgery. Because the three-dimensional (3-D) images of the corneal nerves were acquired in vivo, unintentional movement of the subject during the measurement led to imaging artifacts. These artifacts were compensated for with a series of signal processing techniques, namely realigning A-scan images to flatten the boundary and cross-correlating adjacent B-scan images. To overcome the undesirably large signal from scattering at the corneal surface and iris, volume rendering and maximum intensity projections were performed with only the data taken ...

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    23. Phase variance optical coherence microscopy for label-free imaging of the developing vasculature in zebrafish embryos

      Phase variance optical coherence microscopy for label-free imaging of the developing vasculature in zebrafish embryos

      A phase variance optical coherence microscope (pvOCM) has been created to image blood flow in the microvasculature of zebrafish embryos, without the use of exogenous labels. The pvOCM imaging system has axial and lateral resolutions of 2.8    μ m 2.8  μm in tissue and imaging depth of more than 100    μ m 100  μm . Images of 2 to 5 days postfertilization zebrafish embryos identified the detailed anatomical structure based on OCM intensity contrast. Phase variance contrast offered visualization of blood flow in the arteries, veins, and capillaries. The pvOCM images of the vasculature were confirmed by direct comparisons with fluorescence ...

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    24. Development of a first-generation miniature multiple reference optical coherence tomography imaging device

      Development of a first-generation miniature multiple reference optical coherence tomography imaging device

      Multiple reference optical coherence tomography (MR-OCT) is a technology ideally suited to low-cost, compact OCT imaging. This modality is an extension of time-domain OCT with the addition of a partial mirror in front of the reference mirror. This enables extended, simultaneous depth scanning with the relatively short scan range of a miniature voice coil motor on which the scanning mirror is mounted. This work details early stage development of the first iteration of a miniature MR-OCT device. This iteration utilizes a fiber-coupled input from an off-board superluminescent diode. The dimensions of the module are 40×57  mm40×57  mm ...

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