1. Articles from xiao zhang

    1-15 of 15
    1. Speckle reducing OCT using optical chopper

      Speckle reducing OCT using optical chopper

      Optical coherence tomography (OCT) has been an important and powerful tool for biological research and clinical applications. However, speckle noise significantly degrades the image quality of OCT and has a negative impact on the clinical diagnosis accuracy. In this paper, we propose a novel speckle noise suppression technique which changes the spatial distribution of sample beam using a special optical chopper. Then a series of OCT images with uncorrelated speckle patterns could be captured and compounded to improve the image quality without degradation of resolution. Typical signal-to-noise ratio improvement of ∼6.4 dB is experimentally achieved in tissue phantom imaging ...

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    2. Use of optical coherence tomography angiography for assessment of microvascular changes in the macula and optic nerve head in hypertensive patients without hypertensive retinopathy

      Use of optical coherence tomography angiography for assessment of microvascular changes in the macula and optic nerve head in hypertensive patients without hypertensive retinopathy

      Purpose To compare optical coherence tomography angiography (OCTA) screening parameters of the macula and optic nerve head (ONH) between healthy volunteers and chronic hypertensive patients without hypertensive retinopathy. Methods This was an observational, cross-sectional study. Fifty-seven chronic hypertensive patients without hypertensive retinopathy (22 men and 35 women) and 40 healthy volunteers (17 men and 23 women), ranging in age from 60 to 70 years, were included in this study. Patients and volunteers were divided into three groups and one eye was selected randomly from each participant. Group A comprised patients who had a history of hypertension for >10 years (n ...

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      Mentions: Optovue
    3. Machine-Learning Classification of Port Wine Stain With Quantitative Features of Optical Coherence Tomography Image

      Machine-Learning Classification of Port Wine Stain With Quantitative Features of Optical Coherence Tomography Image

      Port wine stain (PWS) is the benign congenital capillary malformation of skin, occurring in 0.3% to 0.5% of the population. In this paper, we build two automated support vector machine (SVM) based classifiers by extracting quantitative features from normal and PWS tissue images recorded by optical coherence tomography (OCT). We use both full feature set and simplified feature set for training. Accuracy of 92.7%, sensitivity of 92.3% and specificity of 93.8% were obtained for classifier with full feature set. Accuracy of 92.7%, sensitivity of 94.9% and specificity of 87.5% were obtained for ...

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    4. Feature Of The Week 07/22/2019: Tsinghua University Demonstrates A “Sparse Sampled” Smart CCD Camera for Compressed Sensing Optical Coherence Tomography.

      Feature Of The Week 07/22/2019: Tsinghua University Demonstrates A “Sparse Sampled” Smart CCD Camera for Compressed Sensing Optical Coherence Tomography.

      Optical coherence tomography (OCT) is a promising imaging technique in medicine and biology, which allows for obtaining high-resolution, cross-sectional images of biological tissues. In the past decade, the imaging speed of OCT is consistently increasing, and currently OCT can acquire three-dimensional (3D) images in real time with imaging speed up to 10-MHz A-scan rate. With such a high imaging rate, OCT system has to acquire a large amount of data, which is too massive for data transmission and storage. Compressed sensing (CS) technique is a powerful method to solve this problem. It exploits the sparsity property of the signal and ...

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    5. Compressed sensing spectral domain optical coherence tomography with a hardware sparse-sampled camera

      Compressed sensing spectral domain optical coherence tomography with a hardware sparse-sampled camera

      We present a sparse-sampled camera for compressed sensing spectral domain optical coherence tomography (CS SD-OCT), which is mainly composed of a novel mask with specially designed coating and a commercially available CCD camera. The sparse-sampled camera under-samples the SD-OCT spectrum in hardware, thus reduces the acquired image data and can achieve faster A-scan speed than conventional CCD camera with the same pixel number. Compared with a conventional SD-OCT system, the CS SD-OCT system equipped with the sparse-sampled camera has better fall-off and SNR performance. CS-OCT imaging of bio-tissue is also demonstrated.

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    6. Optical coherence tomography angiography analysis of the choriocapillary layer in treatment-naïve diabetic eyes

      Optical coherence tomography angiography analysis of the choriocapillary layer in treatment-naïve diabetic eyes

      Purpose To evaluate the capillary flow density (CFD) of choriocapillary (CC) microvasculature using optical coherence tomography angiography (OCT-A) in diabetic eyes and the association of CFD and systemic and metabolic factors. Methods Cross-sectional study. This study enrolled 282 eyes of 146 subjects, including 43 healthy control eyes, 56 diabetic eyes without diabetic retinopathy (DR), 43 eyes with mild nonproliferative DR (NPDR), 54 eyes with moderate NPDR, 38 eyes with severe NPDR, and 48 eyes with proliferative DR (PDR). CFD was measured in the CC layer. Clinical data were collected. Multiple linear regression analyses were performed to identify associated clinical variables ...

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    7. Optical computing optical coherence tomography with conjugate suppression by dispersion

      Optical computing optical coherence tomography with conjugate suppression by dispersion

      For all imaging techniques, such as optical coherence tomography (OCT), fast imaging speed is always of high demand. Optical computing OCT ( OC2T) has achieved ultrahigh speed for real time 3D imaging without post data processing, but its spatial resolution is lowered down due to an imperfect Fourier transformation in the optical computing process. In this Letter, we illustrate the theory of OC2T and prove that the dispersion imbalance between reference arm and sample arm may be introduced to improve the resolution. Furthermore, this novel OC2T technique can also enable a conjugate restrained OCT imaging without any data processing, achieving ∼ 2 ...

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    8. Conjugate transformation for dispersion compensation in optical coherence tomography imaging

      Conjugate transformation for dispersion compensation in optical coherence tomography imaging

      In optical coherence tomography (OCT), the sample dispersion tends to increase the signal width and hence lower down the resolution, resulting in serious image quality degradation, especially for imaging over a large depth range or media with large dispersion coefficient. In this letter, instead of the conventional Fourier transformation for dispersion compensation that can compensate the image only ideally at a certain depth, a novel transformation, as called conjugate transformation, is proposed to achieve high resolution at all depth by utilizing the conjugate function of the signal itself as an optimized integral kernel. A large dispersion media of ZnSe is ...

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    9. Endoscopic optical coherence tomography with a focus-adjustable probe

      Endoscopic optical coherence tomography with a focus-adjustable probe

      We present a focus-adjustable endoscopic probe for optical coherence tomography (OCT), which is able to acquire images with different focal planes and overcome depth-of-focus limitations by image fusing. The use of a two-way shape-memory-alloy spring enables the probe to adjust working distance over 1.5 mm, providing a large scanning range with high resolution and no sensitivity loss. Equipped with a homemade hollow-core ultrasonic motor, the probe is capable of performing an unobstructed 360 deg field-of-view distal scanning. Both the axial resolution and the best lateral resolution are ∼ 4    μm ∼4  μm , with a sensitivity of 100.3 dB. Spectral-domain ...

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    10. Feature Of The Week 11/26/2016: Tsinghua University Demonstrates Optical Computing Technique and Achieves High Speed OCT of 10 Mega-A-Scans/Second.

      Feature Of The Week 11/26/2016: Tsinghua University Demonstrates Optical Computing Technique and Achieves High Speed OCT of 10 Mega-A-Scans/Second.

      In the past few decades, OCT has been applied in a wide range of applications including clinical and material research areas. For some biomedical applications such as surgical guidance, real-time volumetric OCT (4D-OCT) imaging is in high demand. However, for high definition volumetric imaging in real time, i.e., 1000 pixels along 3 spatial dimensions and 30 volumetric imaging per second, the data flow will be 1000×1000×1000×30=30GVoxel/s. To process these massive data is a big challenge to the performance of current GPUs and CPUs. Professor Ping Xue, Postdoc Xiao Zhang and their colleagues from Tsinghua ...

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    11. Optical computing for optical coherence tomography

      Optical computing for optical coherence tomography

      We propose an all-optical Fourier transformation system for real-time massive data processing in high speed optical coherence tomography (OCT). In the so-called optical computing OCT, fast Fourier transformation (FFT) of A-scan signal is optically processed in real time before being detected by photoelectric detector. Therefore, the processing time for interpolation and FFT in traditional Fourier domain OCT can be dramatically eliminated. A processing rate of 10 mega-A-scans/second was experimentally achieved, which is, to our knowledge, the highest speed for OCT imaging. Due to its fiber based all-optical configuration, this optical computing OCT system is ideal for ultrahigh speed volumetric ...

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    12. Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source

      Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source

      We present an ultrahigh-speed optical coherence tomography (OCT) based on an all-optical swept-source with an A-scan rate of 40 MHz. The inertia-free swept-source, which has its output power of 41.2 mW and tuning range of 40 nm and high scan linearity in wavenumber with Pearson’s correlation coefficients r of 0.9996, consists of a supercontinuum laser, an optical band-pass filter, a linearly chirped fiber Bragg grating, an erbium-doped fiber amplifier, and two buffer stages. With sensitivity of 87 dB, high-speed OCT imaging of biological tissue in vivo is also demonstrated.

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    13. Feature Of The Week 2/2/14: Tsinghua University.Demonstrates Linear-in-Wavenumber Swept Laser with an Acousto-Optic Deflector for OCT

      Feature Of The Week 2/2/14: Tsinghua University.Demonstrates Linear-in-Wavenumber Swept Laser with an Acousto-Optic Deflector for OCT

      Compared to the conventional time domain OCT, the frequency domain (FD) detection techniques enable a dramatic increase in imaging speed. Spectrometer-based FD-OCT (SD-OCT) systems are already widely used, especially for ophthalmic application in the 800 nm wavelength range. Alternatively, the application of FD-OCT systems based on a rapidly swept, narrowband light source, i.e. swept source OCT (SS-OCT) offers the additional advantages of dual balance detection, potentially longer ranging depth and higher imaging speeds. However, a general disadvantage of most FD-OCT systems is the requirement to resample and recalibrate the detected OCT interference fringe prior to fast Fourier transformation, in ...

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    14. Linear-in-wavenumber swept laser with an acousto-optic deflector for optical coherence tomography

      Linear-in-wavenumber swept laser with an acousto-optic deflector for optical coherence tomography

      We report a novel linear-in-wavenumber ( k -linear) swept laser source based on an acousto-optic deflector (AOD). The AOD-based optical filter includes an acousto-optic deflector and a reflection grating. The laser may tune k linearly in wavenumber over time due to its appropriate configuration and is favorable for fast imaging because it avoids data resampling and recalibration, as are required in conventional swept source optical coherence tomography (SS-OCT). We achieved k -linearity with Pearson’s r correlation coefficients of 0.99995 without and 0.99997 with optimization. The laser has a tuning range of 50 nm, a 3 dB swept range ...

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    15. Reproducibility of Optical Coherence Tomography in Multiple Sclerosis

      Background  Optical coherence tomography (OCT) is a promising new method of quantifying axon thickness in the retinal nerve fiber layer (RNFL) that has been used predominantly by ophthalmologists to monitor glaucoma. Optical coherence tomography is being considered as a potential outcome measure in multiple sclerosis (MS) clinical trials, but no data exist on the reproducibility of this technique in MS centers.Objective  To determine the reproducibility of OCT measurement of mean RNFL thickness in the undilated eyes of healthy control subjects and patients with MS.Design  Prospective analysis of 4 healthy controls to determine interrater, intrarater, and longitudinal reproducibility. Cross-sectional ...

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    1-15 of 15
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  2. Topics in the News

    1. (12 articles) Tsinghua University
    2. (12 articles) Ping Xue
    3. (11 articles) Chengming Wang
    4. (7 articles) Ning Zhang
    5. (5 articles) Tianyuan Chen
    6. (2 articles) Jing-gao Zheng
    7. (1 articles) Johns Hopkins University
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    Linear-in-wavenumber swept laser with an acousto-optic deflector for optical coherence tomography Feature Of The Week 2/2/14: Tsinghua University.Demonstrates Linear-in-Wavenumber Swept Laser with an Acousto-Optic Deflector for OCT Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source Optical computing for optical coherence tomography Feature Of The Week 11/26/2016: Tsinghua University Demonstrates Optical Computing Technique and Achieves High Speed OCT of 10 Mega-A-Scans/Second. Endoscopic optical coherence tomography with a focus-adjustable probe Optical computing optical coherence tomography with conjugate suppression by dispersion Compressed sensing spectral domain optical coherence tomography with a hardware sparse-sampled camera Feature Of The Week 07/22/2019: Tsinghua University Demonstrates A “Sparse Sampled” Smart CCD Camera for Compressed Sensing Optical Coherence Tomography. Direct inverse linearization of piezoelectric actuator’s initial loading curve and its applications in full-field optical coherence tomography (FF-OCT) Peripapillary Retinal and Choroidal Perfusion in Nonarteritic Ischemic Optic Neuropathy Using Optical Coherence Tomography Angiography Reliability of foveal avascular zone measurements in eyes with retinal vein occlusion using optical coherence tomography angiography