1. 1-24 of 54 1 2 3 »
    1. Plasma treatment effect on angiogenesis in wound healing process evaluated in vivo using angiographic optical coherence tomography

      Plasma treatment effect on angiogenesis in wound healing process evaluated in vivo using angiographic optical coherence tomography

      Non-thermal atmospheric pressure plasma holds promise for promoting wound healing. However, plasma-induced angiogenesis, which is important to better understand the underlying physics of plasma treatment effect on wound healing, remains largely unknown. We therefore evaluated the effect of non-thermal plasma on angiogenesis during wound healing through longitudinal monitoring over 30 days using non-invasive angiographic optical coherence tomography imaging in vivo . We demonstrate that the plasma-treated vascular wound area of mouse ear was noticeably decreased as compared to that of control during the early days in the wound healing process. We also observed that the vascular area density was increased in ...

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    2. Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

      Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

      A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm ...

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    3. Strategies to improve phase-stability of ultrafast swept source optical coherence tomography for single shot imaging of transient mechanical waves at 16 kHz frame rate

      Strategies to improve phase-stability of ultrafast swept source optical coherence tomography for single shot imaging of transient mechanical waves at 16 kHz frame rate

      We present single-shot phase-sensitive imaging of propagating mechanical waves within tissue, enabled by an ultrafast optical coherence tomography (OCT) system powered by a 1.628 MHz Fourier domain mode-locked (FDML) swept laser source. We propose a practical strategy for phase-sensitive measurement by comparing the phases between adjacent OCT B-scans, where the B-scan contains a number of A-scans equaling an integer number of FDML buffers. With this approach, we show that micro-strain fields can be mapped with ∼3.0 nm sensitivity at ∼16 000 fps. The system's capabilities are demonstrated on porcine cornea by imaging mechanical wave propagation launched by ...

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    4. Microfluidic volumetric flow determination using optical coherence tomography speckle: An autocorrelation approach

      Microfluidic volumetric flow determination using optical coherence tomography speckle: An autocorrelation approach

      Functional modalities of Optical Coherence Tomography (OCT) based on speckle analysis are emerging in the literature. We propose a simple approach to the autocorrelation of OCT signal to enable volumetric flow rate differentiation, based on decorrelation time. Our results show that this technique could distinguish flows separated by 3  μ l/min, limited by the acquisition speed of the system. We further perform a B-scan of gradient flow inside a microchannel, enabling the visualization of the drag effect on the walls.

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    5. Choroidal vasculature characteristics based choroid segmentation for enhanced depth imaging optical coherence tomography image

      Choroidal vasculature characteristics based choroid segmentation for enhanced depth imaging optical coherence tomography image

      Purpose: In clinical research, it is important to measure choroidal thickness when eyes are affected by various diseases. The main purpose is to automatically segment choroid for enhanced depth imaging optical coherence tomography (EDI-OCT) images with five B-scans averaging. Methods: The authors present an automated choroid segmentation method based on choroidal vasculature characteristics for EDI-OCT images with five B-scans averaging. By considering the large vascular of the Haller’s layer neighbor with the choroid-sclera junction (CSJ), the authors measured the intensity ascending distance and a maximum intensity image in the axial direction from a smoothed and normalized EDI-OCT image. Then ...

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    6. Superluminescent diode with a broadband gain based on self-assembled InAs quantum dots and segmented contacts for an optical coherence tomography light source

      Superluminescent diode with a broadband gain based on self-assembled InAs quantum dots and segmented contacts for an optical coherence tomography light source

      We report a broadband-gain superluminescent diode (SLD) based on self-assembled InAs quantum dots (QDs) for application in a high-resolution optical coherence tomography (OCT) light source. Four InAs QD layers, with sequentially shifted emission wavelengths achieved by varying the thickness of the In 0.2 Ga 0.8 As strain-reducing capping layers, were embedded in a conventional p-n heterojunction comprising GaAs and AlGaAs layers. A ridge-type waveguide with segmented contacts was formed on the grown wafer, and an as-cleaved 4-mm-long chip (QD-SLD) was prepared. The segmented contacts were effective in applying a high injection current density to the QDs and obtaining ...

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    7. Automated detection of vessel lumen and stent struts in intravascular optical coherence tomography to evaluate stent apposition and neointimal coverage

      Automated detection of vessel lumen and stent struts in intravascular optical coherence tomography to evaluate stent apposition and neointimal coverage

      Purpose: Intravascular optical coherence tomography (IV-OCT) is a high-resolution imaging method used to visualize the microstructure of arterial walls in vivo . IV-OCT enables the clinician to clearly observe and accurately measure stent apposition and neointimal coverage of coronary stents, which are associated with side effects such as in-stent thrombosis. In this study, the authors present an algorithm for quantifying stent apposition and neointimal coverage by automatically detecting lumen contours and stent struts in IV-OCT images. Methods: The algorithm utilizes OCT intensity images and their first and second gradient images along the axial direction to detect lumen contours and stent strut ...

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    8. Doppler optical coherence microscopy and tomography applied to inner ear mechanics

      Doppler optical coherence microscopy and tomography applied to inner ear mechanics

      While it is clear that cochlear traveling waves underlie the extraordinary sensitivity, frequency selectivity, and dynamic range of mammalian hearing, the underlying micromechanical mechanisms remain unresolved. Recent advances in low coherence measurement techniques show promise over traditional laser Doppler vibrometry and video microscopy, which are limited by low reflectivities of cochlear structures and restricted optical access. Doppler optical coherence tomography (DOCT) and Doppler optical coherence microscopy (DOCM) both utilize a broadband source to limit constructive interference of scattered light to a small axial depth called a coherence gate. The coherence gate can be swept axially to image and measure sub-nanometer ...

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    9. Phase-sensitive optical coherence tomography-based vibrometry using a highly phase-stable akinetic swept laser source

      Phase-sensitive optical coherence tomography-based vibrometry using a highly phase-stable akinetic swept laser source

      Phase-sensitive Optical Coherence Tomography (PhOCT) is an emerging tool for in vivo investigation of the vibratory function of the intact middle and inner ear. PhOCT is able to resolve micron scale tissue morphology in three dimensions as well as measure picometer scale motion at each spatial position. Most PhOCT systems to date have relied upon the phase stability offered by spectrometer detection. On the other hand swept laser source based PhOCT offers a number of advantages including balanced detection, long imaging depths, and high imaging speeds. Unfortunately the inherent phase instability of traditional swept laser sources has necessitated complex user ...

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    10. Optical coherence tomography and low-frequency mechanics: A moderated discussion

      Optical coherence tomography and low-frequency mechanics: A moderated discussion

      The following is an edited transcript of a recorded discussion session on the topics of “Optical Coherence Tomography” and “Low-Frequency Mechanics”. The discussion, moderated by the authors, took place at the 12 th International Workshop on the Mechanics of Hearing held at Cape Sounio, Greece, in June 2014. All participants knew that the session was being recorded. In view of both the spontaneous nature of the discussion and the editing, however, this transcript may not represent the considered or final views of the participants, and may not represent a consensus of experts in the field. The reader is advised to ...

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    11. Development of a phase-sensitive Fourier domain optical coherence tomography system to measure mouse organ of Corti vibrations in two cochlear turns

      Development of a phase-sensitive Fourier domain optical coherence tomography system to measure mouse organ of Corti vibrations in two cochlear turns

      In this study, we have developed a phase-sensitive Fourier-domain optical coherence tomography system to simultaneously measure the in vivo inner ear vibrations in the hook area and second turn of the mouse cochlea. This technical development will enable measurement of intra-cochlear distortion products at ideal locations such as the distortion product generation site and reflection site. This information is necessary to un-mix the complex mixture of intra-cochlear waves comprising the DPOAE and thus leads to the non-invasive identification of the local region of cochlear damage.

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    12. Quantitative contrast-enhanced optical coherence tomography

      Quantitative contrast-enhanced optical coherence tomography

      We have developed a model to accurately quantify the signals produced by exogenous scattering agents used for contrast-enhanced Optical Coherence Tomography (OCT). This model predicts distinct concentration-dependent signal trends that arise from the underlying physics of OCT detection. Accordingly, we show that real scattering particles can be described as simplified ideal scatterers with modified scattering intensity and concentration. The relation between OCT signal and particle concentration is approximately linear at concentrations lower than 0.8 particle per imaging voxel. However, at higher concentrations, interference effects cause signal to increase with a square root dependence on the number of particles within ...

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    13. Polarization-sensitive interferometric synthetic aperture microscopy

      Polarization-sensitive interferometric synthetic aperture microscopy

      Three-dimensional optical microscopy suffers from the well-known compromise between transverse resolution and depth-of-field. This is true for both structural imaging methods and their functional extensions. Interferometric synthetic aperture microscopy (ISAM) is a solution to the 3D coherent microscopy inverse problem that provides depth-independent transverse resolution. We demonstrate the extension of ISAM to polarization sensitive imaging, termed polarization-sensitive interferometric synthetic aperture microscopy (PS-ISAM). This technique is the first functionalization of the ISAM method and provides improved depth-of-field for polarization-sensitive imaging. The basic assumptions of polarization-sensitive imaging are explored, and refocusing of birefringent structures is experimentally demonstrated. PS-ISAM enables high-resolution volumetric imaging ...

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    14. Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

      Measuring retinal blood flow in rats using Doppler optical coherence tomography without knowing eyeball axial length

      Purpose: Doppler optical coherence tomography (OCT) is widely used for measuring retinal blood flow. Existing Doppler OCT methods require the eyeball axial length, in which empirical values are usually used. However, variations in the axial length can create a bias unaccounted for in the retinal blood flow measurement. The authors plan to develop a Doppler OCT method that can measure the total retinal blood flow rate without requiring the eyeball axial length. Methods: The authors measured the retinal blood flow rate using a dual-ring scanning protocol. The small and large scanning rings entered the eye at different incident angles (small ...

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    15. Optical coherence tomography for nondestructive evaluation of fuel rod degradation

      Optical coherence tomography for nondestructive evaluation of fuel rod degradation

      Nuclear power plants regularly inspect fuel rods to ensure safe and reliable operation. Excessive corrosion can cause fuel failures which can have significant repercussions for the plant, including impacts on plant operation, worker exposure to radiation, and the plant's INPO rating. While plants typically inspect for fuel rod corrosion using eddy current techniques, these techniques have known issues with reliability in the presence of tenacious, ferromagnetic crud layers that can deposit during operation, and the nondestructive evaluation (NDE) inspection results can often be in error by a factor of 2 or 3. For this reason, alternative measurement techniques, such ...

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    16. Development and evaluation of a device for simultaneous uniaxial compression and optical imaging of cartilage samples in vitro

      Development and evaluation of a device for simultaneous uniaxial compression and optical imaging of cartilage samples in vitro

      In this paper, we present a system that allows imaging of cartilage tissue via optical coherence tomography (OCT) during controlled uniaxial unconfined compression of cylindrical osteochondral cores in vitro . We describe the system design and conduct a static and dynamic performance analysis. While reference measurements yield a full scale maximum deviation of 0.14% in displacement, force can be measured with a full scale standard deviation of 1.4%. The dynamic performance evaluation indicates a high accuracy in force controlled mode up to 25 Hz, but it also reveals a strong effect of variance of sample mechanical properties on the ...

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    17. Extreme optical confinement in a slotted photonic crystal waveguide

      Extreme optical confinement in a slotted photonic crystal waveguide

      Using Optical Coherence Tomography, we measure the attenuation of slow light modes in slotted photonic crystal waveguides. When the group index is close to 20, the attenuation is below 300 dB cm −1 . Here, the optical confinement in the empty slot is very strong, corresponding to an ultra-small effective cross section of 0.02  μ m 2 . This is nearly 10 times below the diffraction limit at λ  = 1.5  μ m, and it enables an effective interaction with a very small volume of functionalized matter.

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    18. The role of physics in inner-ear physiology and auditory perception

      The role of physics in inner-ear physiology and auditory perception

      Auditory analysis of acoustical stimuli has mainly been connected with Fourier analysis. This touches the basic link between auditory perception and the operation of the hearing organs, namely, physics and mathematics. This relation has amply been demonstrated by the work and ideas of Georg von Békésy. Later, the healthy cochlea (inner ear) was found to contain amplifying elements that boost frequency selectivity. Associated with this there is a pronounced nonlinearity. Furthermore, the ear does not only absorb and process sounds, it also emits sound waves. Mathematical models of all these processes must contain subsets serving them all, a ...

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    19. Noninvasive referencing of intraocular tumors for external beam radiation therapy using optical coherence tomography: A proof of concept

      Noninvasive referencing of intraocular tumors for external beam radiation therapy using optical coherence tomography: A proof of concept

      Purpose: External beam radiation therapy is currently considered the most common treatment modality for intraocular tumors. Localization of the tumor and efficient compensation of tumor misalignment with respect to the radiation beam are crucial. According to the state of the art procedure, localization of the target volume is indirectly performed by the invasive surgical implantation of radiopaque clips or is limited to positioning the head using stereoscopic radiographies. This work represents a proof-of-concept for direct and noninvasive tumor referencing based on anterior eye topography acquired using optical coherence tomography (OCT). Methods: A prototype of a head-mounted device has been developed ...

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    20. The influence of glass fibers on elongational viscosity studied by means of optical coherence tomography and X-ray computed tomography

      The influence of glass fibers on elongational viscosity studied by means of optical coherence tomography and X-ray computed tomography

      We report on the flow characteristics of glass-fiber-reinforced polymers in elongational rheometry. Unlike polymers with geometrically isotropic fillers, glass-fiber-reinforced polymers exhibit flow behavior and rheology that depend heavily on the orientation, the length distribution and the content of the fibers. One of the primary objectives of this study was to determine the effect of fiber orientation, concentration and distribution on the entrance pressure drop by means of optical coherence tomography (OCT), full-field optical coherence microscopy (FF-OCM), and X-ray computed tomography (X-CT). Both pressure drop and melt flow were analyzed using a special elongation die (Thermo Scientific X-Die [3]) for inline ...

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    21. Confocal acoustic radiation force optical coherence elastography using a ring ultrasonic transducer

      Confocal acoustic radiation force optical coherence elastography using a ring ultrasonic transducer

      We designed and developed a confocal acoustic radiation force optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic radiation force in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.

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    22. Development of novel imaging probe for optical∕acoustic radiation imaging (OARI)

      Development of novel imaging probe for optical∕acoustic radiation imaging (OARI)

      Purpose: Optical/acoustic radiation imaging (OARI) is a novel imaging modality being developed to interrogate the optical and mechanical properties of soft tissues. OARI uses acoustic radiation force to generate displacement in soft tissue. Optical images before and after the application of the force are used to generate displacement maps that provide information about the mechanical properties of the tissue under interrogation. Since the images are optical images, they also represent the optical properties of the tissue as well. In this paper, the authors present the first imaging probe that uses acoustic radiation force in conjunction with optical coherence tomography ...

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    23. Guide-star-based computational adaptive optics for broadband interferometric tomography

      Guide-star-based computational adaptive optics for broadband interferometric tomography

      We present a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (“guide stars”) within a three-dimensional broadband interferometric tomogram. This method enables the correction of high-order monochromatic and chromatic aberrations utilizing guide stars that are revealed after numerical compensation of defocus and low-order aberrations of the optical system. Guide-star-based aberration correction in a silicone phantom with sparse sub-resolution-sized scatterers demonstrates improvement of resolution and signal-to-noise ratio over a large isotome. Results in highly scattering muscle tissue showed improved resolution of fine structure over an extended volume. Guide-star-based computational adaptive ...

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    1-24 of 54 1 2 3 »
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