1. Articles from Zhenhe Ma

    1-18 of 18
    1. Cerebral edema detection in vivo after middle cerebral artery occlusion using swept-source optical coherence tomography

      Cerebral edema detection in vivo after middle cerebral artery occlusion using swept-source optical coherence tomography

      Cerebral edema is a severe complication of ischemic cerebrovascular disease, which can lead to microcirculation compression resulting in additional ischemic damage. Real-time and continuous in vivo imaging techniques for edema detection are of great significance to basic research on cerebral edema. We attempted to monitor the cerebral edema status in rats with middle cerebral artery occlusion (MCAO) over time, using a wide field-of-view swept-source optical coherence tomography (SS-OCT) system. Optical attenuation coefficients (OACs) were calculated by an optimized depth-resolved estimation method, and en face OAC maps covering the whole cortex were obtained. Then, the tissue affected by edema was segmented ...

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    2. Simultaneous detection of cerebral blood perfusion and cerebral edema using swept‐source optical coherence tomography

      Simultaneous detection of cerebral blood perfusion and cerebral edema using swept‐source optical coherence tomography

      The progression of ischemic cerebral edema (CE) is closely related to the level of cerebral blood perfusion (CBP) and affects each other. Simultaneous detection of CBP and CE is helpful in understanding the mechanisms of ischemic cerebral edema development. In this article, a wide field of view (FOV) SS‐OCT system was used to detect CE status and CBP levels simultaneously in middle cerebral artery occlusion (MCAO) rats. Images reflecting these two physiological states can be reconstructed with only one C‐scan. We quantify these two physiological states into 4 parameters, which contain two vascular parameters (vascular displacement distance and ...

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    3. In vivo monitoring of thrombosis in mice by optical coherence tomography

      In vivo monitoring of thrombosis in mice by optical coherence tomography

      The objective of this study is to establish a novel method for continuously monitoring thrombus progression with various outcome measures and to assess the efficacy of antithrombotic drugs in murine thrombosis model in mice. In the study, thrombus was induced in the femoral vein of mice by FeCl 3 and monitored over time by spectral‐domain optical coherence tomography (OCT). Three dimensional images of thrombi with or without heparin as an antithrombotic agent were obtained from OCT angiography. In addition, several parameters of thrombi were analysed and compared between control and anticoagulant groups. By using OCT, we were able to ...

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    4. Spectral domain optical coherence tomography with sub-micrometer sensitivity for measurement of central corneal thickness

      Spectral domain optical coherence tomography with sub-micrometer sensitivity for measurement of central corneal thickness

      We demonstrated a method for measurement of central corneal thickness (CCT) with a sub-micrometer sensitivity using a spectral domain optical coherence tomography system without needing a super broad bandwidth light source. By combining the frequency and phase components of Fourier transform, the method is capable of measurement of a large dynamic range with a high sensitivity. Absolute phases are retrieved by comparing the correlations between the detected and simulated interference fringes. The phase unwrapping ability of the present method was quantitatively tested by measuring the displacement of a piezo linear stage. The human CCTs of six volunteers were measured to ...

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      Mentions: Yi Wang
    5. Quantification of cerebral vascular perfusion density via optical coherence tomography based on locally adaptive regional growth

      Quantification of cerebral vascular perfusion density via optical coherence tomography based on locally adaptive regional growth

      Optical coherence tomography (OCT) angiography is a noninvasive imaging modality that produces volumetric views of blood flow perfusion in vivo with resolution at capillary level, which has been widely adopted to monitor cerebral perfusion status after stroke in experimental settings. Accurate quantification of cerebral perfusion from OCT angiograms is important for understanding the cerebral vascular pathophysiology and assessing the treatment of ischemic stroke. Quantification of blood vessels from OCT angiography faces some problems; one is uneven backscatter (which causes some blood vessels to be very bright, some very dark), and the other is that the brightness in the same blood ...

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      Mentions: Yi Wang
    6. Assessment of microvasculature flow state with a high speed all-optic dual-modal system of optical coherence tomography and photoacoustic imaging

      Assessment of microvasculature flow state with a high speed all-optic dual-modal system of optical coherence tomography and photoacoustic imaging

      We propose a high speed all-optic dual-modal system that combines spectral domain optical coherence tomography (SDOCT) and photoacoustic imaging (PAI) to evaluate microvasculature flow states. A homodyne interferometer was used to remotely detect the surface vibration caused by photoacoustic (PA) waves. The PA excitation, PA probing and SDOCT probing beams share the same X-Y galvanometer scanner to perform fast two-dimensional scanning. In addition, we introduced multi-excitation, dual-channel acquisition and sensitivity compensation to improve the imaging speed of the PAI sub-system. The total time for imaging a sample with 256 × 256 pixels is less than 1 minute. The performance of the ...

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      Mentions: Yi Wang
    7. Hemodynamic changes in a rat parietal cortex after endothelin-1-induced middle cerebral artery occlusion monitored by optical coherence tomography

      Hemodynamic changes in a rat parietal cortex after endothelin-1-induced middle cerebral artery occlusion monitored by optical coherence tomography

      A blockage of the middle cerebral artery (MCA) on the cortical branch will seriously affect the blood supply of the cerebral cortex. Real-time monitoring of MCA hemodynamic parameters is critical for therapy and rehabilitation. Optical coherence tomography (OCT) is a powerful imaging modality that can produce not only structural images but also functional information on the tissue. We use OCT to detect hemodynamic changes after MCA branch occlusion. We injected a selected dose of endothelin-1 (ET-1) at a depth of 1 mm near the MCA and let the blood vessels follow a process first of occlusion and then of slow ...

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    8. Measurement of cerebral blood flow rate and its relationship with brain function using optical coherence tomography

      Measurement of cerebral blood flow rate and its relationship with brain function using optical coherence tomography

      Activity of brain neurons will lead to changes in local blood flow rate (BFR). Thus, it is important to measure the local BFR of cerebral cortex on research of neuron activity in vivo, such as rehabilitation evaluation after stroke, etc. Currently, laser Doppler flowmetry is commonly used for blood flow measurement, however, relatively low resolution limits its application. Optical coherence tomography (OCT) is a powerful noninvasive 3D imaging modality with high temporal and spatial resolutions. Furthermore, OCT can provide flow distribution image by calculating Doppler frequency shift which makes it possible for blood flow rate measurement. In this paper, we ...

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    9. Blood flow changes after unilateral carotid artery ligation monitored by optical coherence tomography

      Blood flow changes after unilateral carotid artery ligation monitored by optical coherence tomography

      Unilateral carotid artery ligation which could induce adaptive improvement is a classic model that has been widely used to study pathology of ischemic disease. In those studies, blood flow is an important parameter to characterize the ischemia. Optical coherence tomography (OCT) is a powerful imaging modality which can provide depth resolved images in biological tissue with high spatial and temporal resolution. SPF rats was anesthetized with isoflurane and divided into two groups. In first group, bilateral carotid artery was surgically exposed, and then left carotid artery was ligated. Blood flow changes of the contralateral carotid artery was monitored using high ...

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    10. Measurement of strain and strain rate in embryonic chick heart using spectral domain optical coherence tomography

      Measurement of strain and strain rate in embryonic chick heart using spectral domain optical coherence tomography

      It is important to measure embryonic heart myocardial wall strain and strain rate for understanding the mechanisms of embryonic heart development. Optical coherence tomography (OCT) can provide depth resolved images with high spatial and temporal resolution, which makes it have the potential to reveal the complex myocardial activity in the early stage embryonic heart. We develop a novel method to measure strain in embryonic chick heart based on spectral domain OCT images and subsequent image processing. We perform 4D(x,y,z,t) scanning on the outflow tract (OFT) of chick embryonic hearts in HH18 stage (~3 days of incubation ...

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    11. Blood flowing state analysis in outflow tract of chick embryonic heart based on spectral domain optical coherence tomography

      Blood flowing state analysis in outflow tract of chick embryonic heart based on spectral domain optical coherence tomography

      The cardiac development is a complicated process affected by genetic and environmental factors. Wall shear stress (WSS) and periodic stress (WPS) are the components which have been proved to influence the morphogenesis during early stages of cardiac development. The vessel wall will be deformed by the blood pressure and produce natural elastic force acting on the blood. Because blood flowing in different flow state and show different characteristics of fluid, which influence the calculation of WSS and WPS directly, it is necessary to study the blood flow state. In this paper, we introduce a method to quantify the blood flowing ...

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    12. In vivo assessment of wall strain in embryonic chick heart by spectral domain optical coherence tomography

      In vivo assessment of wall strain in embryonic chick heart by spectral domain optical coherence tomography

      The ability to measure in vivo wall strain in embryonic hearts is important for fully understanding the mechanisms of cardiac development. Optical coherence tomography (OCT) is a powerful tool for the three-dimensional imaging of complex myocardial activities in early-stage embryonic hearts with high spatial and temporal resolutions. We describe a method to analyze periodic deformations of myocardial walls and evaluate in vivo myocardial wall strains with a high-speed spectral domain OCT system. We perform four-dimensional scanning on the outflow tract (OFT) of chick embryonic hearts and determine a special cross-section in which the OFT can be approximated as an annulus ...

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    13. Measurement of wall shear stress in chick embryonic heart using optical coherence tomography

      Measurement of wall shear stress in chick embryonic heart using optical coherence tomography

      The cardiac development is a complicated process affected by genetic and environmental factors. Wall shear stress (WSS) is one of the components which have been proved to influence the morphogenesis during early stages of cardiac development. To study the mechanism, WSS measurement is a step with significant importance. WSS is caused by blood flow imposed on the inner surface of the heart wall and it can be determined by calculating velocity gradients of blood flow in a direction perpendicular to the wall. However, the WSS of the early stage embryonic heart is difficult to measure since the embryonic heart is ...

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      Mentions: Yi Wang
    14. Approach to quantify two-dimensional strain of chick embryonic heart in early stage based on spectral domain optical coherence tomography

      Approach to quantify two-dimensional strain of chick embryonic heart in early stage based on spectral domain optical coherence tomography

      The heart undergoes remarkable changes during embryonic development due to genetic programming and epigenetic influences, in which mechanical loads is a key factor. As embryonic research development, an important goal is to develop mathematical models that describe the influence of mechanics on embryonic heart development. However, basic parameters for the modeling are difficult to acquire since the embryonic heart is tiny and beating fast in the early stages. Optical coherence tomography (OCT) technique provides depth-resolved image with high resolution and high acquisition speed in a noninvasive manner. In this paper, we performed 4D[(x,y,z) + t] scan on the ...

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      Mentions: Yi Wang
    15. Changes in strain and blood flow in the outflow tract of chicken embryo hearts observed with spectral domain optical coherence tomography after outflow tract banding

      Changes in strain and blood flow in the outflow tract of chicken embryo hearts observed with spectral domain optical coherence tomography after outflow tract banding

      In this paper, we demonstrated the use of a spectral domain optical coherence tomography (OCT) in visualizing and quantifying changes in cardiac wall strain and blood-flow velocities under normal and altered hemodynamic conditions in chicken embryos at an early stage of development, focusing on the heart outflow tract (OFT). OCT imaging allowed in vivo evaluation strain and strain rate of the myocardium of the OFT through analyzing the periodic variation of the myocardial wall thickness. We found that alterations in hemodynamic conditions, through OFT banding, Changed strain and blood-flow velocities through the OFT as expected.

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    16. Practical approach for dispersion compensation in spectral-domain optical coherence tomography

      Practical approach for dispersion compensation in spectral-domain optical coherence tomography

      e proposed and demonstrated a digital method of dispersion compensation suitable for spectral-domain optical coherence tomography. The wavelength coordinate of the coherence spectrum was calibrated digitally using a two-order polynomial. A software-based scheme was introduced to determine the polynomial coefficients of the polynomial fitting spectrum wavelength. Therefore, the spectrum deformation introduced by dispersion can be compensated effectively. This method was experimentally validated by in vivo imaging an early-stage chick embryonic heart.

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      Mentions: Yi Wang
    17. Measurement of absolute blood flow velocity in outflow tract of HH18 chicken embryo based on 4D reconstruction using spectral domain optical coherence tomography

      Measurement of absolute blood flow velocity in outflow tract of HH18 chicken embryo based on 4D reconstruction using spectral domain optical coherence tomography

      The measurement of blood-plasma absolute velocity distributions with high spatial and temporal resolution in vivo is important for the investigation of embryonic heart at its early stage of development. We introduce a novel method to measure absolute blood flow velocity based on high speed spectral domain optical coherence tomography (OCT) and apply it to measure velocities across the heart outflow tract (OFT) of a chicken embryo (stage HH18). First, we use the OCT system to acquire 4D 
[(x,y,z) + t] images of the OFT in vivo. Second, we reconstruct the 4D microstructural images and obtain the orientation of the ...

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    1-18 of 18
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  2. Topics in the News

    1. (10 articles) Yi Wang
    2. (5 articles) Ruikang K. Wang
    3. (4 articles) University of Washington
    4. (1 articles) Capital Medical University
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    Measurement of absolute blood flow velocity in outflow tract of HH18 chicken embryo based on 4D reconstruction using spectral domain optical coherence tomography Practical approach for dispersion compensation in spectral-domain optical coherence tomography Changes in strain and blood flow in the outflow tract of chicken embryo hearts observed with spectral domain optical coherence tomography after outflow tract banding Approach to quantify two-dimensional strain of chick embryonic heart in early stage based on spectral domain optical coherence tomography Measurement of wall shear stress in chick embryonic heart using optical coherence tomography In vivo assessment of wall strain in embryonic chick heart by spectral domain optical coherence tomography Blood flowing state analysis in outflow tract of chick embryonic heart based on spectral domain optical coherence tomography Measurement of strain and strain rate in embryonic chick heart using spectral domain optical coherence tomography Blood flow changes after unilateral carotid artery ligation monitored by optical coherence tomography Hemodynamic changes in a rat parietal cortex after endothelin-1-induced middle cerebral artery occlusion monitored by optical coherence tomography Both speckle reduction and contrast enhancement for optical coherence tomography via sequential optimization in the logarithmic domain based on a refined Retinex model OCT parameters of the optic nerve head and the retina as surrogate markers of brain volume in a normal population, a pilot study