1. Articles mentioning both I. Alex Vitkin and University of Toronto

    1-24 of 69 1 2 3 »
    1. Analysis of low-scattering regions in optical coherence tomography: applications to neurography and lymphangiography

      Analysis of low-scattering regions in optical coherence tomography: applications to neurography and lymphangiography
      Analysis of semi-transparent low scattering biological structures in optical coherence tomography (OCT) has been actively pursued in the context of lymphatic imaging, with most approaches relying on the relative absence of signal as a means of detection. Here we present an alternate methodology based on spatial speckle statistics, utilizing the similarity of a distribution of given voxel intensities to the power distribution function of pure noise, to visualize the low-scattering ...
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    2. Preclinical quantitative in-vivo assessment of skin tissue vascularity in radiation-induced fibrosis with optical coherence tomography

      Preclinical quantitative in-vivo assessment of skin tissue vascularity in radiation-induced fibrosis with optical coherence tomography
      Radiation therapy (RT) is widely and effectively used for cancer treatment but can also cause deleterious side effects, such as a late-toxicity complication called radiation-induced fibrosis (RIF). Accurate diagnosis of RIF requires analysis of histological sections to assess extracellular matrix infiltration. This is invasive, prone to sampling limitations, and thus rarely used; instead, current practice relies on subjective clinical surrogates, including visual observation, palpation, and patient symptomatology questionnaires. This preclinical ...
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    3. Optical coherence tomography‐based angiography device with real‐time angiography B‐scans visualization and hand‐held probe for everyday clinical use

      Optical coherence tomography‐based angiography device with real‐time angiography B‐scans visualization and hand‐held probe for everyday clinical use
      This work is dedicated to the development of the OCT system with angiography for everyday clinical use. Two major problems were solved during the development: compensation of specific natural tissue displacements, induced by contact scanning mode and physiological motion of patients (eg, respiratory and cardiac motions) and online visualization of vessel cross‐sections to provide feedback for the system operator.
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    4. Cross-Polarization Optical Coherence Tomography with Active Maintenance of the Circular Polarization of a Sounding Wave in a Common Path System

      Cross-Polarization Optical Coherence Tomography with Active Maintenance of the Circular Polarization of a Sounding Wave in a Common Path System
      We consider a cross-polarization optical coherence tomography system with a common path for the sounding and reference waves and active maintenance of the circular polarization of a sounding wave. The system is based on the formation of birefringent characteristics of the total optical path, which are equivalent to a quarter-wave plate with a 45 orientation of its optical axes with respect to the linearly polarized reference wave. Conditions under which ...
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    5. Alternative Contrast Mechanism in Optical Coherence Tomography: Temporal Speckle Synchronization Effects

      Alternative Contrast Mechanism in Optical Coherence Tomography: Temporal Speckle Synchronization Effects
      We propose an alternative optical coherence tomography (OCT) contrast mechanism based on analysis of speckle temporal synchronization using B-mode OCT structural images. We show that the changes in synchronized speckle intensities with time may be used to distinguish between different tissue types, thus providing a novel and potentially useful contrast for OCT imaging. The developed methodology is tested in scattering flow phantoms, and in vivo on cervical cancer tumour grown ...
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    6. Quantitative Cross-Polarization Optical Coherence Tomography Detection of Infiltrative Tumor Margin in a Rat Glioma Model: a Pilot Study

      Quantitative Cross-Polarization Optical Coherence Tomography Detection of Infiltrative Tumor Margin in a Rat Glioma Model: a Pilot Study
      Determining boundaries of infiltrative glial tumors remains a challenging problem in neurooncology. Optical coherence tomography (OCT) with cross-polarization (CP) visualization is a promising technique as a surgical guidance tool. However, the outcome of the procedures performed under OCT guidance strongly depends on the surgeons qualification. Thus, a quantitative method for assessing resection margins with OCT is required. The aim of this study was to develop a robust quantitative approach for ...
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    7. Preclinical longitudinal imaging of tumor microvascular radiobiological response with functional optical coherence tomography

      Preclinical longitudinal imaging of tumor microvascular radiobiological response with functional optical coherence tomography
      Radiation therapy (RT) is widely used for cancer treatment, alone or in combination with other therapies. Recent RT advances have revived interest in delivering higher dose in fewer fractions, which may invoke both cellular and microvascular damage mechanisms. Microvasculature may thus be a potentially sensitive functional biomarker of RT early response, especially for such emerging RT treatments. However it is difficult to measure directly and non-invasively, and its time course ...
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    8. In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography

      In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography
      Mucositis is the limiting toxicity of radio(chemo)therapy of head and neck cancer. Diagnostics, prophylaxis and correction of this condition demand new accurate and objective approaches. Here we report on an in vivo longitudinal monitoring of the oral mucosa dynamics in 25 patients during the course of radiotherapy of oropharyngeal and nasopharyngeal cancer using multifunctional optical coherence tomography (OCT). A spectral domain OCT system with a specially-designed oral imaging ...
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    9. Pixel classification method in optical coherence tomography for tumor segmentation and its complementary usage with OCT microangiography

      Pixel classification method in optical coherence tomography for tumor segmentation and its complementary usage with OCT microangiography
      A novel machine-learning method to distinguish between tumor and normal tissue in optical coherence tomography (OCT) has been developed. Pre-clinical murine ear model implanted with mouse colon carcinoma CT-26 was used. Structural-image-based feature sets were defined for each pixel and machine learning classifiers were trained using ground truth OCT images manually segmented by comparison with histology. The accuracy of the OCT tumour segmentation method was then quantified by comparing with ...
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    10. K-distribution three-dimensional mapping of biological tissues in optical coherence tomography

      K-distribution three-dimensional mapping of biological tissues in optical coherence tomography
      Probability density function (PDF) analysis with K-distribution model of optical coherence tomography (OCT) intensity signals has previously yielded a good representation of the average number of scatterers in a coherence volume for microspheres-in-water systems, and has shown initial promise for biological tissue characterization. In this work, we extend these previous findings, based on single point M-mode or 2D slice analysis, to full 3D imaging maps of the shape parameter of ...
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    11. Optical coherence elastography for strain dynamics measurements in laser correction of cornea shape

      Optical coherence elastography for strain dynamics measurements in laser correction of cornea shape
      We describe the use of elastographic processing in phase-sensitive optical coherence tomography (OCT) for visualizing dynamics of strain and tissue-shape changes during laser-induced photothermal corneal reshaping, for applications in the emerging field of non-destructive and non-ablative (non-LASIK) laser vision correction. The proposed phase-processing approach based on fairly sparse data acquisition enabled rapid data processing and near-real-time visualization of dynamic strains. The approach avoids conventional phase unwrapping, yet allows for mapping ...
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    12. Polarization image segmentation of radiofrequency ablated porcine myocardial tissue

      Polarization image segmentation of radiofrequency ablated porcine myocardial tissue
      Optical polarimetry has previously imaged the spatial extent of a typical radiofrequency ablated (RFA) lesion in myocardial tissue, exhibiting significantly lower total depolarization at the necrotic core compared to healthy tissue, and intermediate values at the RFA rim region. Here, total depolarization in ablated myocardium was used to segment the total depolarization image into three (core, rim and healthy) zones. A local fuzzy thresholding algorithm was used for this multi-region ...
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    13. Statistical properties of dynamic speckles from flowing Brownian scatterers in the vicinity of the image plane in optical coherence tomography

      Statistical properties of dynamic speckles from flowing Brownian scatterers in the vicinity of the image plane in optical coherence tomography
      A closed-form analytical expression is obtained for the spatio-temporal correlation function of the scattered radiation detected in fiber-based optical coherence tomography (OCT), assuming a clean optical system arrangement in the OCT sample arm. It is shown that the transverse flow component causes purely translational speckle motion with the predicted speckle velocity 2x higher than the velocity of the flowing particles as would be observed in the image plane under incoherent ...
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    14. Multiparameter thermo-mechanical OCT-based characterization of laser-induced cornea reshaping

      Multiparameter thermo-mechanical OCT-based characterization of laser-induced cornea reshaping
      Phase-sensitive optical coherence tomography (OCT) is used for visualizing dynamic and cumulative strains and corneashape changes during laser-produced tissue heating. Such non-destructive (non-ablative) cornea reshaping can be used as a basis of emerging technologies of laser vision correction. In experiments with cartilaginous samples, polyacrilamide phantoms and excised rabbit eyes we demonstrate ability of the developed OCT system to simultaneously characterize transient and cumulated strain distributions, surface displacements, scattering tissue properties ...
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    15. Microvascular contrast enhancement in optical coherence tomography using microbubbles

      Microvascular contrast enhancement in optical coherence tomography using microbubbles
      Gas microbubbles (MBs) are investigated as intravascular optical coherence tomography (OCT) contrast agents. Agar + intralipid scattering tissue phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood + MB. Swept-source structural and speckle variance (sv) OCT images, as well as speckle decorrelation times, were evaluated under both no-flow and varying flow conditions. Faster decorrelation ...
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    16. Optical clearing of melanoma in vivo: characterization by diffuse reflectance spectroscopy and optical coherence tomography

      Optical clearing of melanoma in vivo: characterization by diffuse reflectance spectroscopy and optical coherence tomography
      Melanoma is the most aggressive type of skin cancer, with significant risk of fatality. Due to its pigmentation, light-based imaging and treatment techniques are limited to near the tumor surface, which is inadequate, for example, to evaluate the microvascular density that is associated with prognosis. White-light diffuse reflectance spectroscopy (DRS) and near-infrared optical coherence tomography (OCT) were used to evaluate the effect of a topically applied optical clearing agent (OCA ...
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    17. Analysis of scattering statistics and governing distribution functions in optical coherence tomography

      Analysis of scattering statistics and governing distribution functions in optical coherence tomography
      The probability density function (PDF) of light scattering intensity can be used to characterize the scattering medium. We have recently shown that in optical coherence tomography (OCT), a PDF formalism can be sensitive to the number of scatterers in the probed scattering volume and can be represented by the K-distribution, a functional descriptor for non-Gaussian scattering statistics. Expanding on this initial finding, here we examine polystyrene microsphere phantoms with different ...
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    18. Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability

      Vessel-contrast enhancement in label-free optical coherence angiography based on phase and amplitude speckle variability
      Recently proposed in vivo label-free optical coherence angiography techniques based on phase and amplitude speckle variability often require additional signal pre- and post processing operations to enhance vessel-contrast. We observe here 1) contrast enhancement by optimizing the signal normalization/weighing before processing; 2) algorithm based on Kasai estimator for phase compensation between processed A-scans to reduce masking role of motion artifacts; and 3) image projection through the imaging depth for ...
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    19. Robust strain mapping in optical coherence elastography by combining local phase-resolved measurements and cumulative displacement tracking

      Robust strain mapping in optical coherence elastography by combining local phase-resolved measurements and cumulative displacement tracking
      We report a novel hybrid method of robust strain mapping in compressional optical coherence elastography using combined phase measurements on sub-wavelength-scale and cumulative pixel-scale displacement tracking. This hybrid nature significantly extends the range of measurable displacements and strains in comparison with conventional direct phase-resolved measurements. As a result, the proposed strain-mapping method exhibits significantly increased robustness with respect to both additive noise and decorrelation noise produced by displacements and strains ...
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    20. Blood flow contrast enhancement in optical coherence tomography using microbubbles: a phantom study

      Blood flow contrast enhancement in optical coherence tomography using microbubbles: a phantom study
      In this study gas microbubbles are investigated as intravascular OCT contrast agents. Agar+Intralipid scattering tissue-like phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood and microbubbles. Swept-source structural and speckle variance OCT images, as well as speckle decorrelation times, were evaluated under both stationary and flow conditions. Faster decorrelation times and ...
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    21. Characterization of atherosclerotic plaques by cross-polarization optical coherence tomography

      Characterization of atherosclerotic plaques by cross-polarization optical coherence tomography
      We combined cross-polarization optical coherence tomography (CP OCT) and non-linear microscopy based on second harmonic generation (SHG) and two-photon-excited fluorescence (2PEF) to assess collagen and elastin fibers in the development of the atherosclerotic plaque (AP). The study shows potential of CP OCT for the assessment of collagen and elastin fibers condition in atherosclerotic arteries. Specifically, the additional information afforded by CP OCT, related to birefringence and cross-scattering properties of arterial ...
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    22. Dynamic light scattering by flowing Brownian particles measured with optical coherence tomography: impact of the optical system

      Dynamic light scattering by flowing Brownian particles measured with optical coherence tomography: impact of the optical system
      The study of flowing Brownian particles finds numerous biomedical applications, ranging from blood flow analysis to diffusion research. A mathematical model for the correlation function of laser radiation scattered by flowing Brownian particles measured with fiber-based optical coherence tomography (OCT), which accounts for the effects of sample arm optics, is presented. It is shown that the parameters of an OCT optical system of any complexity can be taken into account ...
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    23. 1-24 of 69 1 2 3 »
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