1. 1-24 of 43 1 2 »
    1. Multi-directional alignment method for three-dimensional optical coherence tomographic images

      Multi-directional alignment method for three-dimensional optical coherence tomographic images

      We propose a new alignment method for three-dimensional optical coherence tomography (OCT) images. Recently, OCT devices have been developed that can capture three-dimensional tomographic images of retina non-contactly and non-invasively. However, eye movement artifacts in scanning make 3D reconstruction and 3D image processing difficult. In this paper, we propose a method to search the best position automatically by using normalized correlation in two directions (vertical and horizontal directions). This paper applied the proposed method to 7 OCT image sets (4 sets of normal retinal images and 3 sets of abnormal retinal images). The generated images by the proposed method are ...

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    2. 4D Reconstruction of the Beating Embryonic Heart From Two Orthogonal Sets of Parallel Optical Coherence Tomography Slice-Sequences

      4D Reconstruction of the Beating Embryonic Heart From Two Orthogonal Sets of Parallel Optical Coherence Tomography Slice-Sequences

      Current methods to build dynamic optical coherence tomography (OCT) volumes of the beating embryonic heart involve synchronization of 2D+time slice-sequences acquired over separate heartbeats. Temporal registration of these sequences is performed either through gating or post-processing. While synchronization algorithms that exclusively rely on image-intrinsic signals allow forgoing external gating hardware, they are prone to error accumulation, require operator-supervised correction, or lead to non-isotropic resolution. Here, we propose an imagebased, retrospective reconstruction technique that uses two sets of parallel 2D+T slice-sequences, acquired perpendicularly to each other, to yield accurate and automatic reconstructions with isotropic resolution. The method utilizes the ...

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    3. Graph-Based Multi-Surface Segmentation of OCT Data Using Trained Hard and Soft Constraints

      Graph-Based Multi-Surface Segmentation of OCT Data Using Trained Hard and Soft Constraints

      Optical Coherence Tomography is a well established image modality in ophthalmology and used daily in the clinic. Automatic evaluation of such datasets requires an accurate segmentation of the retinal cell layers. However, due to the naturally low signal to noise ratio and the resulting bad image quality, this task remains challenging. We propose an automatic graphbased multi-surface segmentation algorithm that internally uses soft constraints to add prior information from a learned model. This improves the accuracy of the segmentation and increase the robustness to noise. Furthermore, we show that the graph size can be greatly reduced by applying a smart ...

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    4. Two wavelength spectral domain optical coherence tomography systems for early stage chicken embryonic heart imaging

      Two wavelength spectral domain optical coherence tomography systems for early stage chicken embryonic heart imaging

      Blood Flow plays an important role during the early stage development of embryogenesis. Spectral domain optical coherence tomography (SDOCT), with high resolution and high acquisition speed, has been widely used in biological tissue imaging in recent years. By evaluation of phase difference between consecutive A-scan lines, SDOCT provides the ability for flow velocity measurement. In order to find the optimize SDOCT system for early stage chicken embryo heart outflow tract (OFT) flow measurement, two spectral domain optical coherence tomography setups were built in our lab with different central wavelength, i.e. 845nm and 1321nm. The performances of the two systems ...

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    5. Characterization of flowing blood optical property under various fibrinogen levels using optical coherence tomography

      Characterization of flowing blood optical property under various fibrinogen levels using optical coherence tomography

      The feasibility of characterization of human blood fibrinogen levels using optical coherence tomography (OCT) was investigated. Three groups of blood samples were reconstituted of red blood cells and, I. phosphate buffered saline, II. plasma with its intrinsic fibrinogen removed and commercial fibrinogen added, III. native plasma with various fibrinogen levels (0-12 g/L). OCT signal slope (OCTSS) of blood was extracted from OCT depth-reflectivity profiles. Effects of hematocrit (HCT) and blood flow on OCTSS of the blood under various fibrinogen concentrations were also studied. The results of blood flowing at 5 mm/sec showed that OCTSS of all the three ...

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    6. Multimodal Retinal Vessel Segmentation from Spectral-Domain Optical Coherence Tomography and Fundus Photography

      Multimodal Retinal Vessel Segmentation from Spectral-Domain Optical Coherence Tomography and Fundus Photography

      Segmenting retinal vessels in optic nerve head (ONH) centered spectral-domain optical coherence tomography (SD-OCT) volumes is particularly challenging due to the projected neural canal opening (NCO) and relatively low visibility in the ONH center. Color fundus photographs provide a relatively high vessel contrast in the region inside the NCO, but have not been previously used to aid the SD-OCT vessel segmentation process. Thus, in this paper, we present two approaches for the segmentation of retinal vessels in SD-OCT volumes that each take advantage of complimentary information from fundus photographs. In the first approach (referred to as the registeredfundus vessel segmentation ...

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    7. Dual Window Dual Bandwidth Spectroscopic Optical Coherence Tomography Metric for Qualitative Scatterer Size Differentiation in Tissues

      Dual Window Dual Bandwidth Spectroscopic Optical Coherence Tomography Metric for Qualitative Scatterer Size Differentiation in Tissues

      This work investigates the autocorrelation bandwidths of dual window (DW) optical coherence tomography (OCT) k-space scattering profile of different-sized microspheres and their correlation to scatterer size. A dual bandwidth (DB) spectroscopic metric defined as the ratio of the 10% to 90% autocorrelation bandwidths is found to change monotonically with microsphere size and gives the best contrast enhancement for scatterer size differentiation in the resulting spectroscopic image. A simulation model supports the experimental results and revealed a trade-off between the smallest detectable scatterer size and the maximum scatterer size in the linear range of the DWDB metric, which depends on the ...

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    8. Application of morphological operators for optic nerve head segmentation in optical coherence tomography images

      Application of morphological operators for optic nerve head segmentation in optical coherence tomography images

      Optical Coherence Tomography (OCT) is an imaging mod-ality that has several advantages (e.g. high resolution and three dimensional imaging) in comparison with other oph-thalmic imaging methods. Retinal structures, such as the optic nerve head (ONH), can be examined in detail. The geometry of the ONH can offer valuable information for the detection of glaucoma, because it is affected by this disease. However, manual examinations are highly subjective. In this study we present an approach using morphological operators for the completely automated segmentation of the ONH region, which is crucial for the further examination of the geometrical parameters that indicate ...

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    9. Quantitative evaluation of transform domains for compressive sampling-based recovery of sparsely sampled volumetric OCT images

      Quantitative evaluation of transform domains for compressive sampling-based recovery of sparsely sampled volumetric OCT images

      Recently, compressive sampling has received significant attention as an emerging technique for rapid volumetric imaging. We have previously investigated volumetric Optical Coherence Tomography (OCT) image acquisition using compressive sampling techniques and showed that it was possible to recover image volumes from a subset of sampled images. Our previous findings used the multi-dimensional wavelet transform as the domain of sparsification for recovering OCT image volumes. In this report, we analyzed and compared the potential and efficiency of three other image transforms to reconstruct the same volumetric OCT image. Two quantitative measures, the Mean Square Error (MSE) and the Structural SIMilarity index ...

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    10. A compact circumferential scanned endoscopic imaging probe using a MEMS-driven pyramidal polygon reflector

      A compact circumferential scanned endoscopic imaging probe using a MEMS-driven pyramidal polygon reflector

      A novel prototype of electrothermal chevron-beam actuator based microelectromechanical systems (MEMS) platform has been successfully developed for circumferential scan. Microassembly technology is utilized to construct this platform, which consists of a MEMS chevron-beam type microactuator and a micro pyramidal polygon reflector. The proposed electrothermal microactuators with a two-stage electrothermal cascaded chevron-beam driving mechanism provide displacement amplification, and thus driving a highly reflective micro-pyramidal polygon reflector to rotate a large angle for light beam scan. This MEMS platform is ultra-compact, supports circumferential imaging capability, and is suitable for endoscopic optical coherence tomography (EOCT) application, for example intravascular cancer detection.

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    11. Real-time Control of Angioplasty Balloon Inflation Based on Feedback from Intravascular Optical Coherence Tomography: Experimental Validation on an Excised Heart and a Beating Heart Model

      Real-time Control of Angioplasty Balloon Inflation Based on Feedback from Intravascular Optical Coherence Tomography: Experimental Validation on an Excised Heart and a Beating Heart Model

      We report on real-time control of balloon inflation inside porcine arteries. In a first step, experiments were done in a coronary artery of an excised heart. In a second step, experiments were done in a beating heart setup providing conditions very close to in vivo conditions without the complications. A programmable syringe pump was used to inflate a compliant balloon in arteries, while intravascular optical coherence tomography (IVOCT) monitoring was performed. In a feedback loop, IVOCT images were processed to provide the balloon diameter values in real-time to control the pump action in order to achieve a target diameter. In ...

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    12. Split-Frame Gimbaled Two-Dimensional MEMS Scanner for Miniature Dual-Axis Confocal Microendoscopes Fabricated by Front-Side Processing

      Split-Frame Gimbaled Two-Dimensional MEMS Scanner for Miniature Dual-Axis Confocal Microendoscopes Fabricated by Front-Side Processing

      In this paper, we introduce a 2-D microelectromechanical systems scanner for 3.2-mm-diameter dual-axis confocal microendoscopes, fabricated exclusively by front-side processing. Compared to conventional bulk micromachining that incorporates back-side etching, the front-side process is simple and thus enables high device yield. By eliminating the back-side etch window, the process yields compact and robust structures that facilitate handling and packaging. An important component of our front-side fabrication is a low-power deep reactive ion etching (DRIE) process that avoids the heating problems associated with standard DRIE. Reducing the RF etch coil power from 2400 to 1500 W leads to elimination of the ...

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    13. BioThreads: A Novel VLIW-Based Chip Multiprocessor for Accelerating Biomedical Image Processing Applications

      BioThreads: A Novel VLIW-Based Chip Multiprocessor for Accelerating Biomedical Image Processing Applications

      We discuss BioThreads, a novel, configurable, extensible system-on-chip multiprocessor and its use in accelerating biomedical signal processing applications such as imaging photoplethysmography (IPPG). BioThreads is derived from the LE1 open-source VLIW chip multiprocessor and efficiently handles instruction, data and thread-level parallelism. In addition, it supports a novel mechanism for the dynamic creation, and allocation of software threads to uncommitted processor cores by implementing key POSIX Threads primitives directly in hardware, as custom instructions. In this study, the BioThreads core is used to accelerate the calculation of the oxygen saturation map of living tissue in an experimental setup consisting of a ...

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    14. Photonic Generation and Wireless Transmission of Linearly/Nonlinearly Continuously Tunable Chirped Millimeter-Wave Waveforms with High Time-Bandwidth Product at W-band

      Photonic Generation and Wireless Transmission of Linearly/Nonlinearly Continuously Tunable Chirped Millimeter-Wave Waveforms with High Time-Bandwidth Product at W-band
      We demonstrate a novel scheme for photonic generation of chirped millimeter-wave (MMW) pulse with ultra-high time-bandwidth product (TBP). By using a fast wavelength sweeping laser with a narrow instantaneous linewidth, wideband/high-power photonic transmitter-mixers, and heterodyne beating technique, continuously tunable chirped MMW waveforms at W-band are generated and detected through wireless transmission. Compared with the reported optical grating based wavelength-to-time mapping techniques for chirped pulse generation, our approach eliminates the problem in limited frequency resolution of grating, which seriously limits the continuity, tunability, and TBP of the generated waveform. Furthermore, by changing the alternating current (AC) waveform of the driving ...
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    15. Measurement of scattering coefficient in PMMA with SiO2 particles by optical coherence tomography

      Measurement of scattering coefficient in PMMA with SiO2 particles by optical coherence tomography
      An experimental evaluation of reduced scattering coefficient in a homogeneous scattering medium is presented. For deriving the reduced scattering coefficient, a scattering coefficient in a weak scattered region is measured by optical coherence tomography and an anisotropic parameter is derived from the measurement of output beam width. The experimental results showed that the proposed method gave the acceptable values by comparing the results from Mie theory.
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    16. Real-time Control of Angioplasty Balloon Inflation Based on Feedback from Intravascular Optical Coherence Tomography: Preliminary Study on an Artery Phantom

      Real-time Control of Angioplasty Balloon Inflation Based on Feedback from Intravascular Optical Coherence Tomography: Preliminary Study on an Artery Phantom

      A method is proposed to achieve computerized control of angioplasty balloon inflation, based on feedback from intravascular optical coherence tomography (IVOCT). Controlled balloon inflation could benefit clinical applications, cardiovascular research, and medical device industry. The proposed method was experimentally tested for balloon inflation within an artery phantom. During balloon inflation, luminal contour of the phantom was extracted from IVOCT images in real-time. Luminal diameter was estimated from the obtained contour and was used in a feedback loop. Based on the estimated actual diameter and a target diameter, a computer controlled a programmable syringe pump to deliver or withdraw liquid in ...

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    17. Imaging of Breast Cancer with Optical Coherence Tomography Needle Probes: Feasibility and Initial Results

      Imaging of Breast Cancer with Optical Coherence Tomography Needle Probes: Feasibility and Initial Results

      Optical coherence tomography (OCT) is a high-resolution imaging modality with the potential to provide in situ assessment to distinguish normal from cancerous tissue. However, limited image penetration depth has restricted its utility. This paper demonstrates the feasibility of an OCT needle probe to perform interstitial imaging deep below the tissue surface. The side-facing needle probe comprises miniaturized focusing optics consisting of no-core and GRIN fiber encased within either a 22- or 23-gauge needle. 3D-OCT volumetric data sets were acquired by rotating and retracting the probe during imaging. We present the first published image of a human breast cancer tumor margin ...

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    18. Tomographic imaging using photonically generated low-coherence terahertz sources

      Tomographic imaging using photonically generated low-coherence terahertz sources
      This paper presents three-dimensional tomographic imaging system by using low-coherence terahertz (THz) sources. In contrast to conventional THz-pulse tomography with femtosecond pulse lasers, the proposed method requires compact and low-cost broadband optical signals such as amplified spontaneous emission (ASE) sources. Operation principle and the first experimental demonstration of tomographic imaging using 300-GHz-band sources are shown.
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    19. Multimodal in vivo skin imaging with integrated optical coherence and multiphoton microscopy

      Multimodal in vivo skin imaging with integrated optical coherence and multiphoton microscopy
      In this paper we demonstrate high resolution, multimodal in vivo imaging of human skin using optical coherence (OCM) and multiphoton microscopy (MPM). These two modalities are integrated into a single instrument to enable simultaneous acquisition and co-registration. The system design and the OCM image processing architecture enable sufficient performance of both modalities for in vivo imaging of human skin. Examples of multimodal in vivo imaging are presented as well as time lapse imaging of blood flow in single capillaries. By making use of multiple intrinsic contrast mechanisms this integrated technique improves the ability to non-invasively visualize living tissue. Integrated OCM ...
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    20. Glucose sensing in flowing blood and Intralipid by laser pulse time-of-flight and optical coherence tomography techniques

      Glucose sensing in flowing blood and Intralipid by laser pulse time-of-flight and optical coherence tomography techniques
      In this paper, we compare the sensitivities of the two optical modalities, laser pulse time-of-flight (TOF) and optical coherence tomography (OCT), in regard to glucose sensing within the range of 0-1000 mg/dl in flowing blood and tissue-mimicking liquid (Intralipid). We show that TOF technique is about twice more sensitive than OCT, as well for blood as for Intralipid measurements. In case of TOF technique, glucose sensitivity in Intralipid is higher than in blood. We speculate that all this is associated with longer pathlengths of detected photons in TOF than in OCT, which is confirmed by comparison with Monte Carlo ...
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    21. Visible Supercontinuum Generation with Sub-nanosecond 532nm Pulses in All-Solid Photonic Bandgap Fiber

      Visible Supercontinuum Generation with Sub-nanosecond 532nm Pulses in All-Solid Photonic Bandgap Fiber
      An all-solid photonic bandgap fiber with the first bandgap from 450nm to 900nm was designed for visible supercontinuum generation. Sub-nanosecond pulses from 532nm microchip laser were launched into this fiber, and the supercontinuum from 532nm to 900nm was obtained. The bright single-mode visible light beam was observed, with the output power of 30mW.
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    22. Toward Spectral-domain Optical Coherence Tomography on a Chip

      Toward Spectral-domain Optical Coherence Tomography on a Chip
      We present experimental results of a spectraldomain optical coherence tomography system based on an integrated optical spectrometer. A 195-channel arrayedwaveguide- grating (AWG) spectrometer with 0.4-nm channel spacing centered at 1300 nm and a 125-channel AWG with 0.16-nm channel spacing centered at 800 nm have been fabricated in silicon oxynitride waveguide technology. Interferometric distance measurements have been performed by launching light from a broadband source into a free-space Michelson interferometer, with its output coupled into the AWG. A maximum imaging depth of 1 mm and axial resolution of 25 ìm and 20 ìm in air are demonstrated for the ...
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    1-24 of 43 1 2 »
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