1. 1-24 of 143 1 2 3 4 5 6 »
    1. Ultra-high sensitive and high resolution optical coherence tomography using a laser induced electromagnetic dipole

      Ultra-high sensitive and high resolution optical coherence tomography using a laser induced electromagnetic dipole

      Utilizing an optical coherence tomography measurement, we have developed a technique that actively uses a dielectric response due to an induced dipole moment caused by a mode-locked pulsed laser light source. Irradiated laser light in the material induces a photo-induced electric dipole resulting in a refractive index change for its strong electric field. Using this technique, we obtained a highly sensitive fundus retina tomogram of a human eye in vivo with a resolution of 1.3  μ m by single scanning for 20 ms using 8 fs mode-locked pulse laser light with a 350 nm spread spectrum.

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    2. High-resolution full-field spatial coherence gated optical tomography using monochromatic light source

      High-resolution full-field spatial coherence gated optical tomography using monochromatic light source

      We demonstrate dispersion free, high-resolution full-field spatial coherence gated optical tomography using spatially incoherent monochromatic light source. Spatial coherence properties of light source were synthesized by means of combining a static diffuser and vibrating multi mode fiber bundle. Due to low spatial coherence of light source, the axial resolution of the system was achieved similar to that of conventional optical coherence tomography which utilizes low temporal coherence. Experimental results of fringe visibility versus optical path difference are presented for varying numerical apertures objective lenses. High resolution optically sectioned images of multilayer onion skin, and red blood cells are presented.

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    3. Monolithically grown multi-color InAs quantum dots as a spectral-shape-controllable near-infrared broadband light source

      Monolithically grown multi-color InAs quantum dots as a spectral-shape-controllable near-infrared broadband light source

      We have grown monolithic multi-color InAs quantum dots (QDs) for use as a near-infrared (NIR) broadband light source. Our previously developed rotational metal mask enables selective-area growth of QD ensembles with emission peak wavelengths controlled by strain-reducing layers thicknesses, varying the emission approximately 1.2–1.3  μ m. The peak shift value was up to 120 nm, and a combined 160-nm-bandwidth emission spectrum was achieved. Further, the emission spectra shapes were controlled using specific optical excitation powers for each QD ensemble. These results demonstrate the effectiveness of multi-color QDs as a spectrum-shape-controllable NIR broadband light source, particularly suited for optical ...

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    4. A high speed three-dimensional spectral domain optical coherence tomography with <2 μm axial resolution using wide bandwidth femtosecond mode-locked laser

      A high speed three-dimensional spectral domain optical coherence tomography with <2 μm axial resolution using wide bandwidth femtosecond mode-locked laser

      We have developed an ultra-high-resolution optical coherence tomography (OCT) equipment, using a 200 nm bandwidth spectrometer and a mode-locked femtosecond laser. We have characterized this OCT, obtaining high spatial resolution in the axial direction of less than 2  μ m in air via single scanning, within only 20 ms. This corresponds to an ultra-high resolution of less than 1.3  μ m for measurements at the fundus retina. High resolution and high speed imaging enables us to selectively obtain a clear three dimensional (3D) lamina cribrosa itself from a 3D optic disc (OD) image in vivo .

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    5. Automatic quantitative analysis of in-stent restenosis using FD-OCT in vivo intra-arterial imaging

      Automatic quantitative analysis of in-stent restenosis using FD-OCT in vivo intra-arterial imaging

      Purpose: A new segmentation technique is implemented for automatic lumen area extraction and stent strut detection in intravascular optical coherence tomography (OCT) images for the purpose of quantitative analysis of in-stent restenosis (ISR). In addition, a user-friendly graphical user interface (GUI) is developed based on the employed algorithm toward clinical use. Methods: Four clinical datasets of frequency-domain OCT scans of the human femoral artery were analyzed. First, a segmentation method based on fuzzy C means (FCM) clustering and wavelet transform (WT) was applied toward inner luminal contour extraction. Subsequently, stent strut positions were detected by utilizing metrics derived from the ...

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    6. Measurement of surface acoustic wave in soft material using swept-source optical coherence tomography

      Measurement of surface acoustic wave in soft material using swept-source optical coherence tomography

      In endoscopic elastography, it is needed to observe small area with high spatial resolution. Optical coherence tomography (OCT) is one of the candidate imaging methods, which has the depth resolution of several 10 μm. In this study, we try to find the propagation velocity of surface acoustic wave (SAW) using a swept-source OCT (SS-OCT). The depth scanning rate in the SS-OCT is rather fast, which is determined by the wavelength sweep of the light source as fast as 20–100 kHz. However, on the other hand, the lateral scanning is limited up to 100 times per second, since it is ...

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    7. High-resolution corneal topography and tomography of fish eye using wide-field white light interference microscopy

      High-resolution corneal topography and tomography of fish eye using wide-field white light interference microscopy

      Topography and tomography of fish cornea is reconstructed using high resolution white light interference microscopy. White light interferograms at different depths were recorded by moving the object axially. For each depth position, five phase shifted interferograms were recorded and analyzed. From the reconstructed phase maps, the corneal topography and hence the refractive index was determined and from amplitude images the cross-sectional image of fish cornea was reconstructed. In the present method, we utilize a nearly common-path interference microscope and wide field illumination and hence do not require any mechanical B-scan. Therefore, the phase stability of the recorded data is improved.

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    8. Quantitative phase imaging of human red blood cells using phase-shifting white light interference microscopy with colour fringe analysis

      Quantitative phase imaging of human red blood cells using phase-shifting white light interference microscopy with colour fringe analysis

      We report quantitative phase imaging of human red blood cells (RBCs) using phase-shifting interference microscopy. Five phase-shifted white light interferograms are recorded using colour charge coupled device camera. White light interferograms were decomposed into red, green, and blue colour components. The phase-shifted interferograms of each colour were then processed by phase-shifting analysis and phase maps for red, green, and blue colours were reconstructed. Wavelength dependent refractive index profiles of RBCs were computed from the single set of white light interferogram. The present technique has great potential for non-invasive determination of refractive index variation and morphological features of cells and tissues.

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    9. Quantitative measurement on optical attenuation coefficient of cell lines 5-8F and 6-10B using optical coherence tomography

      Quantitative measurement on optical attenuation coefficient of cell lines 5-8F and 6-10B using optical coherence tomography

      Oncogenesis and metastasis of tumor are difficult to detect during the clinic therapy. To explore the optical properties of tumorigenesis and metastasis in nasopharyngeal carcinoma (NPC), we assessed the NPC cell lines 5-8F and 6-10B by optical coherence tomography (OCT): first, the OCT images of the two different types of cell pellets were captured. Second, by fitting Beer’s law to the averaged A-scans in these OCT datasets, the attenuation coefficients ( μ t ) of the cells were extracted. The median attenuation coefficients (interquartile range (IQR)) of 5-8F and 6-10B were 6.79 mm −1 (IQR 6.52 to 7.23 mm ...

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    10. Optical assessment of tissue anisotropy in ex vivo distended rat bladders

      Optical assessment of tissue anisotropy in ex vivo distended rat bladders

      Microstructural remodelling in epithelial layers of various hollow organs, including changes in tissue anisotropy, are known to occur under mechanical distension and during disease processes. In this paper, we analyze how bladder distension alters wall anisotropy using polarized light imaging (followed by Mueller matrix decomposition). Optical retardance values of different regions of normal rat bladders under different distension pressures are derived. Then optical coherence tomography is used to measure local bladder wall thicknesses, enabling the calculation of the tissue birefringence maps as a measure of the tissue anisotropy. Selected two-photon microscopy is also performed to better understand the compositional origins ...

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    11. Synergistic effect of hyperosmotic agents and sonophoresis on breast tissue optical properties and permeability studied with spectral domain optical coherence tomography

      Synergistic effect of hyperosmotic agents and sonophoresis on breast tissue optical properties and permeability studied with spectral domain optical coherence tomography

      Hyperosmotic agents have shown great potential in tissue optical clearing. However, the low efficiency of the permeation in biological tissues seriously restricts its application in reality. The synergy of sonophoresis as a penetration enhancer and hyperosmotic agents, 20% glucose (G) and 20% mannitol (M), in optical clearing has been investigated by analyzing the variation of the attenuation coefficients and the permeability coefficients. In the sonophoresis experiments, ultrasound (US) was applied for 10 min before applying hyperosmotic agents. Along with the administration of hyperosmotic agents, the samples were monitored with optical coherence tomography (OCT) functional imaging for the next 2 h ...

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    12. Study of optical properties and proteoglycan content of tendons by polarization sensitive optical coherence tomography

      Study of optical properties and proteoglycan content of tendons by polarization sensitive optical coherence tomography

      The highly orientated collagen fibers in tendons play a critical role for transferring tensile stress, and they demonstrate birefringent optical properties. However, the influence that proteoglycans (PGs) have on the optical properties of tendons is yet to be fully elucidated. PGs are the essential components of the tendon extracellular matrix; the changes in their quantities and compositions have been associated with tendinopathies. In this study, polarization sensitive optical coherence tomography (PS-OCT) has been used to reveal the relationship between PG content/location and birefringence properties of tendons. Fresh chicken tendons were imaged at regular intervals by PS-OCT and polarization light ...

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      Mentions: Ying Yang
    13. Command functions of open loop galvanometer scanners with optimized duty cycles

      Command functions of open loop galvanometer scanners with optimized duty cycles

      The paper approaches the problem of the command functions of galvanometer-based scanners (GS) that are necessary to produce the linear plus parabolic scanning function of the GS, which we have proved previously to produce the highest possible duty cycle (i.e., time efficiency) of the device. We have completed this theoretical aspect (which contradicted what has been stated previously in the literature, where it has been considered that the linear plus sinusoidal scanning function was the best) with the experimental study of the most used scanning functions of the GSs (sawtooth, sinusoidal and triangular), with applications in biomedical imaging, in ...

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    14. Autocorrelation noise removal for optical coherence tomography by sparse filter design

      Autocorrelation noise removal for optical coherence tomography by sparse filter design

      We present a reconstruction method to eliminate the autocorrelation noise (ACN) in optical coherence tomography (OCT). In this method, the optical fields scattered from the sample features are regarded as the response of a sparse finite impulse response (FIR) filter. Then the OCT reconstruction is formulated as one of identifying the parameters of a sparse FIR filter, which are obtained via an ℓ1 optimization with soft thresholding. The experimental results show that the proposed method can obtain OCT reconstruction results with effective attenuation of ACN.

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    15. Phase-sensitive optical coherence tomography characterization of pulse-induced trabecular meshwork displacement in ex vivo nonhuman primate eyes

      Phase-sensitive optical coherence tomography characterization of pulse-induced trabecular meshwork displacement in ex vivo nonhuman primate eyes

      Glaucoma is a blinding disease for which intraocular pressure (IOP) is the only treatable risk factor. The mean IOP is regulated through the aqueous outflow system, which contains the trabecular meshwork (TM). Considerable evidence indicates that trabecular tissue movement regulates the aqueous outflow and becomes abnormal during glaucoma; however, such motion has thus far escaped detection. The purpose of this study is to describe anovel use of a phase-sensitive optical coherence tomography (PhS-OCT) method to assess pulse-dependent TM movement. For this study, we used enucleated monkey eyes, each mounted in an anterior segment holder. A perfusion system was used to ...

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    16. A Clean Sweep for MEMS-VCSELs

      A Clean Sweep for MEMS-VCSELs

      The first integrated 1310 nm wavelengthMEMS-VCSELs have been reported in this issue of Electronics Lettersby collaborating researchers in the US. Optimised specifically for swept-sourceoptical coherence tomography (SS-OCT) applications, these MEMS-VCSELs can also becontinuously tuned over 150 nm, which is the largest tuning rangeof any surface emitting diode lasers at any wavelength. “MEMS-VCSELshave previously demonstrated speed and coherence length advantages for SS-OCT,but questions remained as to whether MEMS-VCSEL tuning range couldcompete with widely tunable external-cavity lasers,” said Dr Vijaysekhar Jayaramanfrom Praevium Research who took the lead on the designand fabrication. “We believe that this work demonstrates for thefirst time that ...

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    17. Frequency domain multiplexing for speckle reduction in optical coherence tomography

      Frequency domain multiplexing for speckle reduction in optical coherence tomography

      Quantitative analysis of optical coherence tomography data can be strongly hampered by speckle. Here, we introduce a new method to reduce speckle, which leverages from Fourier-domain configurations and operates on individual axial scans. By subdividing the digitized spectrum into a number of distinct narrower windows, each with a different center frequency, several independent speckle patterns result. These can be averaged to yield a lower-resolution image with strongly reduced speckle. The full resolution image remains available for human interpretation; the low resolution version can be used for parametric imaging or quantitative analysis. We demonstrate this technique using intravascular optical frequency domain ...

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    18. Simultaneous optical coherence tomography and autofluorescence microscopy with a single light source

      Simultaneous optical coherence tomography and autofluorescence microscopy with a single light source

      We have accomplished simultaneous spectral domain optical coherence tomography (SD-OCT) and autofluorescence (AF) microscopy with a broadband light source centered at 415 nm. The light source was provided by frequency-doubling of an ultra-fast broadband Ti:Sapphire laser. With a bandwidth of 8 nm, the visible SD-OCT achieved a depth resolution of ∼ 12  μm. Since the two imaging modalities are provided by the same group of photons, their images are intrinsically registered. The dual-modal system is capable of providing OCT imaging and molecular contrasts simultaneously. The imaging system was tested on imaging biological samples ex vivo and in vivo

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    19. Graphics processing unit-based dispersion encoded full-range frequency-domain optical coherence tomography

      Graphics processing unit-based dispersion encoded full-range frequency-domain optical coherence tomography

      Dispersion encoded full-range (DEFR) frequency-domain optical coherence tomography (FD-OCT) and its enhanced version, fast DEFR, utilize dispersion mismatch between sample and reference arm to eliminate the ambiguity in OCT signals caused by non-complex valued spectral measurement, thereby numerically doubling the usable information content. By iteratively suppressing asymmetrically dispersed complex conjugate artifacts of OCT-signal pulses the complex valued signal can be recovered without additional measurements, thus doubling the spatial signal range to cover the full positive and negative sampling range. Previously the computational complexity and low processing speed limited application of DEFR to smaller amounts of data and did not allow ...

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    20. Real-time reference A-line subtraction and saturation artifact removal using graphics processing unit for high-frame-rate Fourier-domain optical coherence tomography video imaging

      Real-time reference A-line subtraction and saturation artifact removal using graphics processing unit for high-frame-rate Fourier-domain optical coherence tomography video imaging

      Variations in the spectral shape and the amplitude of the optical coherence tomography (OCT) signal and reference cause fixed-pattern noise and light reflected from a highly specular surface might cause saturation artifacts. In real-time video-rate OCT imaging, these effects make the OCT video image appear unstable and difficult to view. To eliminate these problems, we implemented real-time reference A-line subtraction and saturation detection and correction on standard Fourier-domain optical coherence tomography (FD-OCT) video imaging frame-by-frame. This real-time OCT data processing method eliminates the need for the physical reference measurement procedure and automatically detects and corrects saturated A-scans if there is ...

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    21. SU‐E‐I‐90: Fast and Robust Algorithm Towards Vessel Lumen and Stent Strut Detection in Optical Coherence Tomography

      SU‐E‐I‐90: Fast and Robust Algorithm Towards Vessel Lumen and Stent Strut Detection in Optical Coherence Tomography

      Purpose: Optical Coherence Tomography (OCT) is a catheter‐based imaging method that employs near‐infrared light to produce high‐resolution cross‐sectional intravascular images. We propose a new segmentation technique for automatic lumen area extraction and stent strut detection in intravascular OCT images for the purpose of quantitative analysis of neointimal hyperplasia (NIH). Methods: Two clinical dataset of frequency‐domainOCT scans of the human femoral artery were analyzed. First, a segmentation method based on Fuzzy C‐Means (FCM) clustering and Wavelet Transform (WT) was applied towards inner luminal contour extraction. Subsequently, stent strut positions were detected by utilizing metrics derived ...

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    22. Automated Stokesmetric imaging laser radar system

      Automated Stokesmetric imaging laser radar system

      We report the design and implementation of a high-speed, automated laser radar (ladar) system with sensitivity enhanced by a polarimetric imaging technique. This ladar is able to analyze the Stokes vector of the reflected light from a target at video-rate. With a polarization state generator and a polarization state analyzer, the system is capable of performing a complete Mueller matrix imaging of the scene under observation. This polarization-sensitive ladar (pladar) is applied to various scenes and found to yield the ability to detect information that is indiscernible to a conventional, intensity-based ladar

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    23. Ultrahigh-speed non-invasive widefield angiography

      Ultrahigh-speed non-invasive widefield angiography

      tinal and choroidal vascular imaging is an important diagnostic benefit for ocular diseases such as age-related macular degeneration. The current gold standard for vessel visualization is fluorescence angiography. We present a potential non-invasive alternative to image blood vessels based on functional Fourier domain optical coherence tomography (OCT). For OCT to compete with the field of view and resolution of angiography while maintaining motion artifacts to a minimum, ultrahigh-speed imaging has to be introduced. We employ Fourier domain mode locking swept source technology that offers high quality imaging at an A-scan rate of up to 1.68 MHz. We present retinal ...

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    24. Label-free subcellular 3D live imaging of preimplantation mouse embryos with full-field optical coherence tomography

      Label-free subcellular 3D live imaging of preimplantation mouse embryos with full-field optical coherence tomography

      Early patterning and polarity is of fundamental interest in preimplantation embryonic development. Label-free subcellular 3D live imaging is very helpful to its related studies. We have developed a novel system of full-field optical coherence tomography (FF-OCT) for noninvasive 3D subcellular live imaging of preimplantation mouse embryos with no need of dye labeling. 3D digitized embryos can be obtained by image processing. Label-free 3D live imaging is demonstrated for the mouse embryos at various typical preimplantation stages with a spatial resolution of 0.7 µm and imaging rate of 24 fps. Factors that relate to early patterning and polarity, such as ...

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    1-24 of 143 1 2 3 4 5 6 »
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