1. Articles from Chaoliang Chen

    1-12 of 12
    1. Optical coherence tomography for dynamic axial correction of an optical end-effector for robot-guided surgical laser ablation

      Optical coherence tomography for dynamic axial correction of an optical end-effector for robot-guided surgical laser ablation

      Robot-guided laser ablation for surgical applications potentially offers many advantages compared to by-hand mechanical tissue cutting. However, given that tissue can be rough and/or uneven, ablation quality can be compromised if the beam waist deviates significantly from the target tissue surface. Therefore, we present a method that uses optical coherence tomography (OCT) for dynamic refocusing of robot-guided surgical laser ablation. A 7-DOF robotic manipulator with an OCT-equipped optical payload was used to simulate robotic guided laser osteotomy. M-mode OCT feedback is used for continuous surface detection to correct for axial deviations along the ablation path due to surface nonuniformity ...

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    2. 2D MEMS-based high-speed beam-shifting technique for speckle noise reduction and flow rate measurement in optical coherence tomography

      2D MEMS-based high-speed beam-shifting technique for speckle noise reduction and flow rate measurement in optical coherence tomography

      In this manuscript, a two-dimensional (2D) micro-electro-mechanical system (MEMS)-based, high-speed beam-shifting spectral domain optical coherence tomography (MHB-SDOCT) is proposed for speckle noise reduction and absolute flow rate measurement. By combining a zigzag scanning protocol, the frame rates of 45.2 Hz for speckle reduction and 25.6 Hz for flow rate measurement are achieved for in-vivo tissue imaging. Phantom experimental results have shown that by setting the incident beam angle to ϕ = 4.76° (between optical axis of objective lens and beam axis) and rotating the beam about the optical axis in 17 discrete angular positions, 91% of speckle ...

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    3. Beam-shifting technique for speckle reduction and flow rate measurement in optical coherence tomography

      Beam-shifting technique for speckle reduction and flow rate measurement in optical coherence tomography

      In this Letter, we propose a beam-shifting optical coherence tomography scheme for speckle reduction and blood flow rate calculation, where variations of the speckle pattern and Doppler angle were generated by parallel shifting of the sample beam incident on the objective lens. The resultant optical coherent tomography images could then be averaged for speckle noise reduction and simultaneously analyzed for flow rate measurement. The performance of the proposed technique was verified by both phantom and in vivo experiments.

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    4. Buffer-averaging super-continuum source based spectral domain optical coherence tomography for high speed imaging

      Buffer-averaging super-continuum source based spectral domain optical coherence tomography for high speed imaging

      In super-continuum (SC) source based spectral domain optical coherence tomography (SC-SDOCT), the stability of the power spectral density (PSD) has a significant impact on OCT system sensitivity and image signal to noise ratio (SNR). High speed imaging decreases the camera's exposure time, thus each A-scan contained fewer laser pulse excited SC wideband emissions, resulting in a decrease of SNR. In this manuscript, we present a buffer-averaging SC-SDOCT (BASC-SDOCT) to improve the system's performance without losing imaging speed, taking advantage of the excess output power from typical SC sources. In our proposed technique, the output light from SC was ...

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    5. Gabor optical coherence tomographic angiography (GOCTA) (Part I): human retinal imaging in vivo

      Gabor optical coherence tomographic angiography (GOCTA) (Part I): human retinal imaging in vivo

      Recently, parallel high A-line speed and wide field imaging for optical coherence tomography angiography (OCTA) has become more prevalent, resulting in a dramatic increase of data quantity which poses a challenge for real time imaging even for GPU in data processing. In this manuscript, we propose a new OCTA processing technique, Gabor optical coherence tomographic angiography (GOCTA), for label-free human retinal angiography imaging. In spectral domain optical coherence tomography (SDOCT), k-space resampling and Fourier transform (FFT) are required for the entire data set of interference fringes to calculate blood flow information in previous OCTA algorithms, which are computationally intensive. As ...

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    6. High speed, wide velocity dynamic range Doppler optical coherence tomography (Part V): Optimal utilization of multi-beam scanning for Doppler and speckle variance microvascular imaging

      High speed, wide velocity dynamic range Doppler optical coherence tomography (Part V): Optimal utilization of multi-beam scanning for Doppler and speckle variance microvascular imaging

      In this paper, a multi-beam scanning technique is proposed to optimize the microvascular images of human skin obtained with Doppler effect based methods and speckle variance processing. Flow phantom experiments were performed to investigate the suitability for combining multi-beam data to achieve enhanced microvascular imaging. To our surprise, the highly variable spot sizes (ranging from 13 to 77 μm) encountered in high numerical aperture multi-beam OCT system imaging the same target provided reasonably uniform Doppler variance and speckle variance responses as functions of flow velocity, which formed the basis for combining them to obtain better microvascular imaging without scanning penalty ...

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    7. Multi-beam optical coherence tomography for microvascular imaging of human skin in vivo

      Multi-beam optical coherence tomography for microvascular imaging of human skin in vivo

      In this paper, a multi-beam optical coherence tomography (OCT) was used to reconstruct the microvascular image of human skin in vivo with phase resolved Doppler OCT (PRDOCT), phase resolved Doppler variance (PRDV) and speckle variance OCT (svOCT), in which the blood flow image was calculated by averaging the four blood flow images obtained by the four beams. In PRDOCT method, it is difficult to detect the blood flow perpendicular to optical axis of the probe beam for single beam OCT, but the multi-beam scanning method can solve this because the input angles of the four probe beams are slightly different ...

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    8. Differential standard deviation of log-scale intensity based optical coherence tomography angiography

      Differential standard deviation of log-scale intensity based optical coherence tomography angiography

      In this paper, a differential standard deviation of log-scale intensity (DSDLI) based optical coherence tomography angiography (OCTA) is presented for calculating microvascular images of human skin. The DSDLI algorithm calculates the variance in difference images of two consecutive log-scale intensity based structural images from the same position along depth direction to contrast blood flow. The en face microvascular images were then generated by calculating the standard deviation of the differential log-scale intensities within the specific depth range, resulting in an improvement in spatial resolution and SNR in microvascular images compared to speckle variance OCT and power intensity differential method. The ...

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    9. Imaginary part-based correlation mapping optical coherence tomography for imaging of blood vessels in vivo

      Imaginary part-based correlation mapping optical coherence tomography for imaging of blood vessels in vivo

      We present an imaginary part-based correlation mapping optical coherence tomography (IMcmOCT) technique for in vivo blood vessels imaging. In the conventional correlation mapping optical coherence tomography (cmOCT) method, two adjacent frames of intensity-based structural images are correlated to extract blood flow information and the size of correlation window has to be increased to improve the signal-to-noise ratio of microcirculation maps, which may cause image blur and miss the small blood vessels. In the IMcmOCT method, the imaginary part of a depth-resolved complex analytic signal in two adjacent B-scans is correlated to reconstruct microcirculation maps. Both phantom and in vivo experiments ...

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    10. 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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    11. The cross-correlation in spectral domain based Doppler optical coherence tomography

      The cross-correlation in spectral domain based Doppler optical coherence tomography

      We propose a cross-correlation method which is based on the cross-correlation of two adjacent A-scans of interferogram fringe for imaging the velocities of the blood flowing in vessels. The method was tested by measurements of the velocities of flowing particles within a glass capillary with known mean velocities. Mean standard deviations of flow velocities of the particles determined through the proposed method were compared to those by the conventional phase resolved method. I n vivo imaging of a mouse ear was performed and the Doppler flow velocity maps were reconstructed by both methods. The experimental results demonstrated that the proposed ...

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    12. 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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    1-12 of 12
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  2. Topics in the News

    1. (10 articles) Nanjing University of Science and Technology
    2. (8 articles) Ryerson University
    3. (8 articles) Wanrong Gao
    4. (8 articles) Victor X. D. Yang
    5. (6 articles) University of Toronto
    6. (5 articles) Sunnybrook Health Sciences Centre
    7. (4 articles) Massachusetts General Hospital
    8. (3 articles) Joel Ramjist
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    Self-spectral calibration for spectral domain optical coherence tomography The cross-correlation in spectral domain based Doppler optical coherence tomography Cube data correlation-based imaging of small blood vessels Imaginary part-based correlation mapping optical coherence tomography for imaging of blood vessels in vivo Differential standard deviation of log-scale intensity based optical coherence tomography angiography Multi-beam optical coherence tomography for microvascular imaging of human skin in vivo High speed, wide velocity dynamic range Doppler optical coherence tomography (Part V): Optimal utilization of multi-beam scanning for Doppler and speckle variance microvascular imaging Gabor optical coherence tomographic angiography (GOCTA) (Part I): human retinal imaging in vivo Buffer-averaging super-continuum source based spectral domain optical coherence tomography for high speed imaging Optical coherence tomography for dynamic axial correction of an optical end-effector for robot-guided surgical laser ablation Image contrast correction method in full-field optical coherence tomography Evaluation of posterior vitreous detachment using ultrasonography and optical coherence tomography