1. I. Alex Vitkin

    0 Comments Leave a Comment

    1-15 of 66 1 2 3 4 5 »
    1. Mentioned In 66 Articles

    2. 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 ...
      Read Full Article
    3. 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 ...
      Read Full Article
    4. 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 ...
      Read Full Article
    5. 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 ...
      Read Full Article
    6. 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 ...
      Read Full Article
    7. 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 ...
      Read Full Article
    8. 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 ...
      Read Full Article
    9. 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 ...
      Read Full Article
    10. 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 ...
      Read Full Article
    11. 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 ...
      Read Full Article
    12. 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 ...
      Read Full Article
    13. 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 ...
      Read Full Article
    14. 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 ...
      Read Full Article
    15. 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 ...
      Read Full Article
    16. 1-15 of 66 1 2 3 4 5 »
  1. Categories

    1. Applications:

      Art, Cardiology, Dentistry, Dermatology, Developmental Biology, Gastroenterology, Gynecology, Microscopy, NDE/NDT, Neurology, Oncology, Ophthalmology, Other Non-Medical, Otolaryngology, Pulmonology, Urology
    2. Business News:

      Acquisition, Clinical Trials, Funding, Other Business News, Partnership, Patents
    3. Technology:

      Broadband Sources, Probes, Tunable Sources
    4. Miscellaneous:

      Jobs & Studentships, Student Theses, Textbooks
  2. About I. Alex Vitkin

    I. Alex Vitkin

    Alex Vitkin is an engineering physicist/biomedical engineer by training, with further specialization in medical physics and applications of lasers in medicine. He is currently a professor of Medical Biophysics and Radiation Oncology at the University of Toronto, a senior scientist in the division of BioPhysics and BioImaging at the Ontario Cancer Institute, and a clinical medical physicist at Princess Margaret Hospital (all in Toronto, Ontario, Canada). His research is the field of biophotonics, with particular emphasis on optical coherence tomography, tissue polarimetry, and optical fiber sensors. He has published over 140 papers and book chapters on diagnostic and therapeutic uses of light in biomedicine, holds several patents in the field, and currently runs a large laboratory with several undergraduate/graduate students and post-doctoral/clinical fellows. His laboratory works closely with clinicians and with industry, and he is a consultant for several biophotonics companies. He has been a Guest Editor for the Optics and Photonics News special issue on Biophotonics, for the Journal of Applied Physics special issue on Applied Biophysics, for the Journal of Biomedical Optics special issue on Advanced Coherence Domain Methods, and currently serves as a topical editor of Optics Letters (second 3-year term). He has lectured widely at national and international levels, including delivering special seminars and summer school modules on biophotonics in Mexico, Brazil, Taiwan, New Zealand, Ukraine, Germany, USA, Cyprus, and Russia; he is currently an active participant in the SPIE Visiting Lecturer and OSA Travelling Lecturer programs. Dr. Vitkin is also a board-certified medical physicist through the CanadianCollege of Physicists in Medicine (CCPM), and a Fellow of the Optical Society of America (OSA) and of the Society of Photo-Optical Instrumentation Engineers (SPIE).