1. 1-17 of 17
    1. Video-rate volumetric optical coherence tomography-based microangiography

      Video-rate volumetric optical coherence tomography-based microangiography

      Video-rate volumetric optical coherence tomography (vOCT) is relatively young in the field of OCT imaging but has great potential in biomedical applications. Due to the recent development of the MHz range swept laser sources, vOCT has started to gain attention in the community. Here, we report the first in vivo video-rate volumetric OCT-based microangiography (vOMAG) system by integrating an 18-kHz resonant microelectromechanical system (MEMS) mirror with a 1.6-MHz FDML swept source operating at ∼ 1.3    μ m ∼1.3  μm wavelength. Because the MEMS scanner can offer an effective B-frame rate of 36 kHz, we are able to engineer vOMAG ...

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    2. Interferometric system based on swept source-optical coherence tomography scheme applied to the measurement of distances of industrial interest

      Interferometric system based on swept source-optical coherence tomography scheme applied to the measurement of distances of industrial interest

      We used an interferometric technique based on typical optical coherence tomography (OCT) schemes for measuring distances of industrial interest. The system employed as a light source a tunable erbium-doped fiber laser of ∼ 20 - pm ∼20-pm bandwidth with a tuning range between 1520 and 1570 nm. It has a sufficiently long coherence length to enable long depth range imaging. A set of fiber Bragg gratings was used as a self-calibration method, which has the advantage of being a passive system that requires no additional electronic devices. The proposed configuration and the coherence length of the laser enlarge the range of maximum ...

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    3. Enhanced optical coherence tomography imaging using a histogram-based denoising algorithm

      Enhanced optical coherence tomography imaging using a histogram-based denoising algorithm

      A histogram-based denoising algorithm was developed to effectively reduce ghost artifact noise and enhance the quality of an optical coherence tomography (OCT) imaging system used to guide surgical instruments. The noise signal is iteratively detected by comparing the histogram of the ensemble average of all A-scans, and the ghost artifacts included in the noisy signal are removed separately from the raw signals using the polynomial curve fitting method. The devised algorithm was simulated with various noisy OCT images, and > 87 % of the ghost artifact noise was removed despite different locations. Our results show the feasibility of selectively and effectively removing ...

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    4. Study of dual-source Fourier-domain optical coherence tomography

      Study of dual-source Fourier-domain optical coherence tomography

      Optical coherence tomography (OCT) is a very high-resolution imaging technique whose resolution depends on source bandwidth. Improving resolution is an important topic of research in OCT. Thus, to improve resolution, the bandwidth of the source must be increased. Practical sources have finite bandwidth. Therefore, it is suggested to use more sources. Previous work expected that resolution will be inevitably improved without mentioning to what extent it will be improved and without any referencing to the effect of spectral separation between the sources. We study the resolution of a Fourier-domain OCT (FD-OCT) system based on two sources. First, we show to ...

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    5. Cube data correlation-based imaging of small blood vessels

      Cube data correlation-based imaging of small blood vessels

      We present a cube data correlation-based correlation mapping optical coherence tomography (cube-cmOCT) method to reconstruct small blood vessel maps. In the cube-cmOCT method, the two adjacent cube data are correlated to extract blood flow information. Both phantom experiments and in vivo experiments were performed to demonstrate the advantage of the proposed method in improving the SNR of blood vessel maps without increasing the window size in the x z plane and offering a clear image of the small blood vessels almost missed by the conventional cmOCT method.

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    6. Numerical simulation validation of nonuniform, nonharmonic analysis of spectral-domain optical coherence tomography

      Numerical simulation validation of nonuniform, nonharmonic analysis of spectral-domain optical coherence tomography

      In spectral-domain optical coherence tomography (SD-OCT), the limited resolution of the spectrometer causes nonuniformity of the interference signal. The latter, in turn, causes the sensitivity of SD-OCT to decrease, thereby limiting the imaging range and decreasing the axial resolution. We addressed this problem by applying nonuniform, nonharmonic analysis (NUNHA) with software that features high-frequency resolution without interpolation. We demonstrate the application of NUNHA in SD-OCT and compare it with conventional frequency analysis methods by simulating nonuniform interference signals. The results suggest that application of NUNHA in SD-OCT can provide acquisition of a clearer tomographic image, accurate analysis of fine and ...

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    7. Parallel guidance endoscopic optical coherence tomography system for internal diagnosis through active cannulas

      Parallel guidance endoscopic optical coherence tomography system for internal diagnosis through active cannulas

      A parallel guidance endoscopic optical coherence tomography (OCT) system is proposed for minimally invasive internal inspection of inner organs or complex structures for diagnosis. The system is maneuvered to access the target using an active cannulas’ steerable structures. The integration of a specially designed linkage device with the developed system allows the OCT endoscope to scan with enhanced signal-collective performance, while maintaining its tip at a constant distance from the target, as well as expanding the scanning range. The proposed system is integrated with flexible active cannulas, and this prototype is used for testing. The test results show that the ...

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    8. Improving axial resolution in spectral domain low-coherence interferometry through fast Fourier transform harmonic artifacts

      Improving axial resolution in spectral domain low-coherence interferometry through fast Fourier transform harmonic artifacts

      Low-coherence interferometric setups in the Fourier domain can experience false structures after the Fourier transform procedure due to signal saturation; in fact, these structures are located at multiple frequencies of the original signal, also referred to as harmonics. This study aids in a better understanding of this phenomenon. The aim of the present work was to show that these features can be used to improve differential axial resolution in highly reflective samples. Using an optical coherence tomography system and calibrated step height standards, it was possible to achieve a resolution greater than the light source coherence length.

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      Mentions: Marcus P. Raele
    9. Three-dimensional speckle reduction in optical coherence tomography through structural guided filtering

      Three-dimensional speckle reduction in optical coherence tomography through structural guided filtering

      Optical coherence tomography (OCT) is a high-resolution noninvasive technology used in medical imaging for the spatial visualization of biological tissue. Due to its coherent nature, OCT suffers from speckle noise, which significantly degrades the information content of resulting scans. We introduce a new filtering method for three-dimensional OCT images, inspired by film grain removal techniques. By matching structural relatedness along all dimensions, the algorithm builds up vector paths for every voxel in the image volume representing its structural neighborhood. Then, by considering the information redundancy along these paths, our filter is able to reduce speckle noise significantly while simultaneously preserving ...

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    10. Simultaneously measuring the refractive index and thickness of an optical sample by using improved fiber-based optical coherence tomography

      Simultaneously measuring the refractive index and thickness of an optical sample by using improved fiber-based optical coherence tomography

      An improved structure for the optical coherence tomography (OCT) scheme based on a 4 × 4 fiber coupler for simultaneously measuring the refractive index and thickness of optical samples is presented. The proposed structure incorporates the optical path length difference of interference light and is used to calculate the refractive index and thickness of an unknown sample without any prior knowledge of the sample parameters. Two methods (time-domain and Fourier-domain OCT) of obtaining information about an unknown sample are proposed, and a high-speed high-resolution OCT system was developed.

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      Mentions: Hsu-Chih Cheng
    11. Intraocular lens alignment from an en face optical coherence tomography image Purkinje-like method

      Intraocular lens alignment from an en face optical coherence tomography image Purkinje-like method

      Measurement of intraocular lens (IOL) alignment implanted in patients in cataract surgery is important to understand their optical performance. We present a method to estimate tilt and decentration of IOLs based on optical coherence tomography (OCT) images. En face OCT images show Purkinje-like images that correspond to the specular reflections from the corneal and IOL surfaces. Unlike in standard Purkinje-imaging, the tomographic nature of OCT allows unequivocal association of the reflection with the corresponding surface. The locations of the Purkinje-like images are linear combinations of IOL tilt, IOL decentration, and eye rotation. The weighting coefficients depend on the individual anterior ...

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    12. Shift-multiplexing complex spectral-domain optical coherence tomography

      Shift-multiplexing complex spectral-domain optical coherence tomography

      We propose and experimentally demonstrate a shift-multiplexing complex spectral-domain optical coherence tomography (shift-multiplexing CSD-OCT) method, in which the maximum detection depth of SD-OCT can be greatly extended by incorporating the shift-multiplexing of detection positions with CSD-OCT. The tomographic imaging with twofold or threefold microscopic slides as the target sample is performed. The experimental results show that the tomographic imaging with more uniform brightness and clarity for the different depth regions in a thick sample can be achieved by the shift-multiplexing CSD-OCT system. In particular, even while the sample’s depth is beyond the maximum imaging depth of CSD-OCT system, the ...

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    13. Integrated optical coherence tomography and reflectometry system for ocular anterior segment imaging and tear film thickness evaluation

      Integrated optical coherence tomography and reflectometry system for ocular anterior segment imaging and tear film thickness evaluation

      We report an integrated optical coherence tomography (OCT) and reflectometry system for ophthalmology imaging. The dual-functional device provides a complementary high-resolution tear film evaluation by reflectometry and anterior segment imaging by OCT, offering a more comprehensive anterior segment examination. The imaging measurement capabilities have been demonstrated on a human eye as well as on a model eye. The minimum measured tear film thickness is 0.3 μ m with measurement resolution of less than ± 0.58 % of film thickness yet the OCT anterior segment offers a depth resolution of 7 μ m with a 45-nm bandwidth superluminescent light source at 840-nm center ...

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    14. Nondestructive metrology by optical coherence tomography empowering manufacturing iterations of layered polymeric optical materials

      Nondestructive metrology by optical coherence tomography empowering manufacturing iterations of layered polymeric optical materials

      In recent years, there has been an ever-growing interest in exploring different optical materials and components to develop compact and effective optical systems. The design and fabrication of high-performance optics require nondestructive metrology techniques to inspect the samples. We have investigated the capability of optical coherence tomography (OCT) to nondestructively characterize layered polymeric materials. Using a custom developed Gabor-domain optical coherence microscopy system centered at 800 nm with 120 nm full width at half maximum enabling unprecedented 2 μ m resolution both laterally and axially in an 8     mm 3 volume, we investigated the internal structure of 50 μ m thick films ...

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    15. Self-spectral calibration for spectral domain optical coherence tomography

      Self-spectral calibration for spectral domain optical coherence tomography

      A different real-time self-wavelength calibration method for spectral domain optical coherence tomography is presented in which interference spectra measured from two arbitrary points on the tissue surface are used for calibration. The method takes advantages of two favorable conditions of optical coherence tomography (OCT) signal. First, the signal back-scattered from the tissue surface is generally much stronger than that from positions in the tissue interior, so the spectral component of the surface interference could be extracted from the measured spectrum. Second, the tissue surface is not a plane and a phase difference exists between the light reflected from two different ...

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    16. Signal processing in optical coherence tomography for aerospace material characterization

      Signal processing in optical coherence tomography for aerospace material characterization

      Based on a customized time-domain optical coherence tomography (OCT) system, a series of signal processing approaches have been designed and reviewed. To improve demodulation accuracy and image quality, demodulation approaches such as median filter, Hilbert transform, and envelope detector were investigated with simulated as well as experimental data. Without noise, the Hilbert transform has the best performance, but after considering the narrow-band noise in the modulated signal, the envelope detector was selected as the ideal demodulation technique. To reduce noise and enhance image contrast, digital signal processing techniques such as a bandpass filtering and two-dimensional median filtering were applied before ...

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    17. Real-time surface tracking system using common-path spectral domain optical coherence tomography

      Real-time surface tracking system using common-path spectral domain optical coherence tomography

      An enhanced surface tracking system based on optical coherence tomography (OCT) modality has been developed and tested for use in a surgical guidance system. A surface detection algorithm based on a Savitzky-Golay filter of A-scan data and thresholding was applied to real-time depth tracking. The algorithm output controlled a motorized stage to adjust the probe position according to the sample’s topological variance in real-time. As a result, the root mean square error (RMSE: 4.2 μ m) of our algorithm was relatively lower than the conventional method (RMSE: 16.6 μ m). Also, OCT images obtained using the algorithm showed a ...

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    1-17 of 17
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