1. Articles from Adrian Mariampillai

    1-25 of 25
    1. Histogram flow mapping with optical coherence tomography for in vivo skin angiography of hereditary hemorrhagic telangiectasia

      Histogram flow mapping with optical coherence tomography for in vivo skin angiography of hereditary hemorrhagic telangiectasia

      Speckle statistics of flowing scatterers have been well documented in the literature. Speckle variance optical coherence tomography exploits the large variance values of intensity changes in time caused mainly by the random backscattering of light resulting from translational activity of red blood cells to map out the microvascular networks. A method to map out the microvasculature malformation of skin based on the time-domain histograms of individual pixels is presented with results obtained from both normal skin and skin containing vascular malformation. Results demonstrated that this method can potentially map out deeper blood vessels and enhance the visualization of microvasculature in ...

      Read Full Article
    2. Detecting apoptosis in vivo and ex vivo using spectroscopic OCT and dynamic light scattering

      Detecting apoptosis in vivo and ex vivo using spectroscopic OCT and dynamic light scattering

      We present an in vivo implementation of a multi-parametric technique for detecting apoptosis using optical coherence tomography in a mouse tumor model. Solid tumors were grown from acute myeloid leukemia cells in the hind leg of SCID mice and treated with a single dose of cisplatin and dexamethasone to induce apoptosis. Both spectral features and speckle decorrelation times indicated good consistency between control mice and reasonable agreement with in vitro measurements. The integrated backscatter increased significantly in tumors responding to treatment while the spectral slope and decorrelation time did not show significant changes. This study demonstrates the feasibility of using ...

      Read Full Article
    3. Optical coherence tomography detection of shear wave propagation in MCF7 cell modules

      Optical coherence tomography detection of shear wave propagation in MCF7 cell modules

      In this work, we explored the potential of measuring shear wave propagation using Optical Coherence Elastography (OCE) in MCF7 cell modules (comprised of MCF7 cells and collagen) and based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a piezoelectric transducer transmitting sine-wave bursts of 400 μs, synchronized with an OCT swept source wavelength sweep imaging system. Acoustic radiation force was applied to the MCF7 cell constructs. Differential OCT phase maps, measured with and without the acoustic radiation force, demonstrate microscopic displacement generated by shear wave propagation in these modules. The OCT phase maps are acquired ...

      Read Full Article
    4. Optical coherence tomography detection of shear wave propagation in inhomogeneous tissue equivalent phantoms and ex-vivo carotid artery samples

      Optical coherence tomography detection of shear wave propagation in inhomogeneous tissue equivalent phantoms and ex-vivo carotid artery samples

      In this work, we explored the potential of measuring shear wave propagation using optical coherence elastography (OCE) in an inhomogeneous phantom and carotid artery samples based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a piezoelectric transducer transmitting sine-wave bursts of 400 μs duration, applying acoustic radiation force (ARF) to inhomogeneous phantoms and carotid artery samples, synchronized with a swept-source OCT (SS-OCT) imaging system. The phantoms were composed of gelatin and titanium dioxide whereas the carotid artery samples were embedded in gel. Differential OCT phase maps, measured with and without the ARF, detected the microscopic ...

      Read Full Article
    5. Review of speckle and phase variance optical coherence tomography to visualize microvascular networks

      Review of speckle and phase variance optical coherence tomography to visualize microvascular networks

      High-resolution mapping of microvasculature has been applied to diverse body systems, including the retinal and choroidal vasculature, cardiac vasculature, the central nervous system, and various tumor models. Many imaging techniques have been developed to address specific research questions, and each has its own merits and drawbacks. Understanding, optimization, and proper implementation of these imaging techniques can significantly improve the data obtained along the spectrum of unique research projects to obtain diagnostic clinical information. We describe the recently developed algorithms and applications of two general classes of microvascular imaging techniques: speckle-variance and phase-variance optical coherence tomography (OCT). We compare and contrast ...

      Read Full Article
    6. Optical coherence tomography detection of shear wave propagation in layered tissue equivalent phantoms

      Optical coherence tomography detection of shear wave propagation in layered tissue equivalent phantoms

      In this work, we explored the potential of measuring shear wave propagation using Optical Coherence Elastography (OCE) in a layered phantom and based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a piezoelectric transducer transmitting sine-wave bursts of 400 μs, synchronized with an OCT swept source wavelength sweep imaging system. The acoustic radiation force was applied to layered phantoms. The phantoms were composed of gelatin and titanium dioxide. Differential OCT phase maps, measured with and without the acoustic radiation force, demonstrate microscopic displacement generated by shear wave propagation in these phantoms of different stiffness. The ...

      Read Full Article
    7. In vivo feasibility of endovascular Doppler optical coherence tomography

      In vivo feasibility of endovascular Doppler optical coherence tomography

      Feasibility of detecting intravascular flow using a catheter based endovascular optical coherence tomography (OCT) system is demonstrated in a porcine carotid model in vivo. The effects of A-line density, radial distance, signal-to-noise ratio, non-uniform rotational distortion (NURD), phase stability of the swept wavelength laser and interferometer system on Doppler shift detection limit were investigated in stationary and flow phantoms. Techniques for NURD induced phase shift artifact removal were developed by tracking the catheter sheath. Detection of high flow velocity (~51 cm/s) present in the porcine carotid artery was obtained by phase unwrapping techniques and compared to numerical simulation, taking ...

      Read Full Article
    8. Real-time speckle variance swept-source optical coherence tomography using a graphics processing unit

      Real-time speckle variance swept-source optical coherence tomography using a graphics processing unit

      Abstract: Advances in swept source laser technology continues to increase the imaging speed of swept-source optical coherence tomography (SS-OCT) systems. These fast imaging speeds are ideal for microvascular detection schemes, such as speckle variance (SV), where interframe motion can cause severe imaging artifacts and loss of vascular contrast. However, full utilization of the laser scan speed has been hindered by the computationally intensive signal processing required by SS-OCT and SV calculations. Using a commercial graphics processing unit that has been optimized for parallel data processing, we report a complete high-speed SS-OCT platform capable of real-time data acquisition, processing, display, and ...

      Read Full Article
    9. Feasibility of optical coherence elastography measurements of shear wave propagation in homogeneous tissue equivalent phantoms

      Feasibility of optical coherence elastography measurements of shear wave propagation in homogeneous tissue equivalent phantoms

      In this work, we explored the potential of measuring shear wave propagation using optical coherence elastography (OCE) based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a 20 MHz piezoelectric transducer (circular element 8.5 mm diameter) transmitting sine-wave bursts of 400 μs, synchronized with the OCT swept source wavelength sweep. The acoustic radiation force (ARF) was applied to two gelatin phantoms (differing in gelatin concentration by weight, 8% vs. 14%). Differential OCT phase maps, measured with and without the ARF, demonstrate microscopic displacement generated by shear wave propagation in these phantoms of different stiffness ...

      Read Full Article
    10. Speckle variance optical coherence tomography of the rodent spinal cord: in vivo feasibility

      Speckle variance optical coherence tomography of the rodent spinal cord: in vivo feasibility

      Optical coherence tomography (OCT) has the combined advantage of high temporal (µsec) and spatial (less than 10µm) resolution. These features make it an attractive tool to study the dynamic relationship between neural activity and the surrounding blood vessels in the spinal cord, a topic that is poorly understood. Here we present work that aims to optimize an in vivo OCT imaging model of the rodent spinal cord. In this study we image the microvascular networks of both rats and mice using speckle variance OCT. This is the first report of depth resolved imaging of the in vivo spinal cord using ...

      Read Full Article
    11. Neurosurgical hand-held optical coherence tomography (OCT) forward-viewing probe

      Neurosurgical hand-held optical coherence tomography (OCT) forward-viewing probe

      A prototype neurosurgical hand-held optical coherence tomography (OCT) imaging probe has been developed to provide micron resolution cross-sectional images of subsurface tissue during open surgery. This new ergonomic hand-held probe has been designed based on our group's previous work on electrostatically driven optical fibers. It has been packaged into a catheter probe in the familiar form factor of the clinically accepted Bayonet shaped neurosurgical non-imaging Doppler ultrasound probes. The optical design was optimized using ZEMAX simulation. Optical properties of the probe were tested to yield an ~20 um spot size, 5 mm working distance and a 3.5 mm ...

      Read Full Article
    12. Endovascular optical coherence tomography intensity kurtosis: visualization of vasa vasorum in porcine carotid artery

      Endovascular optical coherence tomography intensity kurtosis: visualization of vasa vasorum in porcine carotid artery

      lication of speckle variance optical coherence tomography (OCT) to endovascular imaging faces difficulty of extensive motion artifacts inherently associated with arterial pulsations in addition to other physiological movements. In this study, we employed a technique involving a fourth order statistical method, kurtosis, operating on the endovascular OCT intensity images to visualize the vasa vasorum of carotid artery in vivo and identify its flow dynamic in a porcine model. The intensity kurtosis technique can distinguish vasa vasorum from the surrounding tissues in the presence of extensive time varying noises and dynamic motions of the arterial wall. Imaging of vasa vasorum and ...

      Read Full Article
    13. Dual-core ytterbium fiber amplifier for high-power 1060 nm swept source multichannel optical coherence tomography imaging

      Dual-core ytterbium fiber amplifier for high-power 1060 nm swept source multichannel optical coherence tomography imaging
      A novel (to our knowledge) dual-core ytterbium (Yb3+) doped fiber, as an optically pumped amplifier, boosts the output power from a 1060 nm swept source laser beyond 250 mW, while providing a wavelength tuning range of 93 nm, for optical coherence tomography (OCT) imaging. The design of the dual-core Yb-doped fiber amplifier and its multiple wavelength optical pumping scheme to optimize output bandwidth are discussed. Use of the dual-core fiber amplifier showed no appreciable degradation to the coherence length of the seed laser. The signal intensity improvement of this amplifier is demonstrated on a multichannel in vivo OCT imaging system ...
      Read Full Article
    14. Detecting apoptosis using dynamic light scattering with optical coherence tomography

      Detecting apoptosis using dynamic light scattering with optical coherence tomography
      A dynamic light scattering technique is implemented using optical coherence tomography (OCT) to measure the change in intracellular motion as cells undergo apoptosis. Acute myeloid leukemia cells were treated with cisplatin and imaged at a frame rate of 166 Hz using a 1300 nm swept-source OCT system at various times over a period of 48 h. Time correlation analysis of the speckle intensities indicated a significant increase in intracellular motion 24 h after treatment. This rise in intracellular motion correlated with histological findings of irregularly shaped and fragmented cells indicative of cell membrane blebbing and fragmentation.
      Read Full Article
    15. Optimized speckle variance OCT imaging of microvasculature

      Optimized speckle variance OCT imaging of microvasculature
      We optimize speckle variance optical coherence tomography (svOCT) imaging of microvasculature in high and low bulk tissue motion scenarios. To achieve a significant level of image contrast, frame rates must be optimized such that tissue displacement between frames is less than the beam radius. We demonstrate that higher accuracy estimates of speckle variance can enhance the detection of capillaries. These findings are illustrated in vivo by imaging the dorsal window chamber model (low bulk motion). We also show svOCT imaging of the nonstabilized finger (high bulk motion), using optimized imaging parameters, demonstrating better vessel detection than Doppler OCT.
      Read Full Article
    16. Simultaneous 6-channel optical coherence tomography using a high-power telescope-less polygon-based swept laser in dual amplifier configuration

      Simultaneous 6-channel optical coherence tomography using a high-power telescope-less polygon-based swept laser in dual amplifier configuration
      Multichannel optical coherence tomography (MOCT) imaging is demonstrated using a high-power wavelength-swept laser source. The main benefit of MOCT is faster image acquisition rates without a corresponding increase in the laser tuning speed. The wavelength-swept laser was constructed using a compact telescope-less polygon-based filter in Littman arrangement. High output power, necessary for MOCT, was achieved by incorporating two serial semiconductor optical amplifiers in a ring laser cavity in Fourier domain mode-locked configuration. The laser has a measured wavelength tuning range of 111 nm centered at 1329 nm, coherence length of 5.5 mm, and total average output power of 131 ...
      Read Full Article
    17. Doppler optical coherence tomography for interventional cardiovascular guidance: in vivo feasibility and forward-viewing probe flow phantom demonstration

      Doppler optical coherence tomography for interventional cardiovascular guidance: in vivo feasibility and forward-viewing probe flow phantom demonstration
      We demonstrate the potential of a forward-looking Doppler optical coherence tomography (OCT) probe for color flow imaging in several commonly seen narrowed artery morphologies. As a proof of concept, we present imaging results of a surgically exposed thrombotic occlusion model that was imaged superficially to demonstrate that Doppler OCT can identify flow within the recanalization channels of a blocked artery. We present Doppler OCT images in which the flow is nearly antiparallel to the imaging direction. These images are acquired using a flexible 2.2-mm-diam catheter that used electrostatic actuation to scan up to 30 deg ahead of the distal ...
      Read Full Article
    18. In vivo endoscopic multi-beam optical coherence tomography

      In vivo endoscopic multi-beam optical coherence tomography
      multichannel optical coherence tomography (multi-beam OCT) system and an in vivo endoscopic imaging probe were developed using a swept-source OCT system. The distal optics were micro-machined to produce a high numerical aperture, multi-focus fibre optic array. This combination resulted in a transverse design resolution of <10 µm full width half maximum (FWHM) throughout the entire imaging range, while also increasing the signal intensity within the focus of the individual channels. The system was used in a pre-clinical rabbit study to acquire in vivo structural images of the colon and ex vivo images of the oesophagus and trachea. A good correlation ...
      Read Full Article
    19. High-power wavelength-swept laser in Littman telescope-less polygon filter and dual-amplifier configuration for multichannel optical coherence tomography

      High-power wavelength-swept laser in Littman telescope-less polygon filter and dual-amplifier configuration for multichannel optical coherence tomography
      We report a high-power wavelength-swept laser source for multichannel optical coherence tomography (OCT) imaging. Wavelength tuning is performed by a compact telescope-less polygon-based filter in Littman arrangement. High output power is achieved by incorporating two serial semiconductor optical amplifiers in the laser cavity in Fourier domain mode-locked configuration. The measured wavelength tuning range of the laser is 111 nm centered at 1329 nm, coherence length of 5.5 mm, and total average output power of 131 mW at 43 kHz sweeping rate. Multichannel simultaneous OCT imaging at an equivalent A-scan rate of 258 kHz is demonstrated. © 2009 Optical Society of ...
      Read Full Article
    20. Oxygen-independent degradation of HIF- via bioengineered VHL tumour suppressor complex

      Tumour hypoxia promotes the accumulation of the otherwise oxygen-labile hypoxia-inducible factor (HIF)- subunit whose expression is associated with cancer progression, poor prognosis and resistance to conventional radiation and chemotherapy. The oxygen-dependent degradation of HIF- is carried out by the von Hippel-Lindau (VHL) protein-containing E3 that directly binds and ubiquitylates HIF- for subsequent proteasomal destruction. Thus, the cellular proteins involved in the VHL-HIF pathway have been recognized as attractive molecular targets for cancer therapy. However, the various compounds designed to inhibit HIF- or HIF-downstream targets, although promising, have shown limited success in the clinic. In the present study, we describe the ...
      Read Full Article
    21. Interstitial Doppler Optical Coherence Tomography as a Local Tumor Necrosis Predictor in Photodynamic Therapy of Prostatic Carcinoma: An In vivo Study

      We have tested the feasibility of real-time localized blood flow measurements, obtained with interstitial (IS) Doppler optical coherence tomography (DOCT), to predict photodynamic therapy (PDT)-induced tumor necrosis deep within solid Dunning rat prostate tumors. IS-DOCT was used to quantify the PDT-induced microvascular shutdown rate in s.c. Dunning prostate tumors (n = 28). Photofrin (12.5 mg/kg) was administered 20 to 24 hours before tumor irradiation, with 635 nm surface irradiance of 8 to 133 mWcm–2 for 25 minutes. High frequency ultrasound and calipers were used to measure the thickness of the skin covering the tumor and the ...
      Read Full Article
    22. Intravital high-resolution optical imaging of individual vessel response to photodynamic treatment

      Mamta Khurana, Eduardo H. Moriyama, Adrian Mariampillai et al. Intravital imaging using confocal microscopy facilitates high-resolution studies of cellular and molecular events in vivo. We use this, complemented by Doppler optical coherence tomography (OCT), to assess blood flow in a mouse dorsal skin-fold window chamber model to image the response of individua ... [J. Biomed. Opt. 13, 040502 (2008)] published Fri Aug 29, 2008.
      Read Full Article
    23. High power wavelength linearly swept mode locked fiber laser for OCT imaging

      We report a long coherence length, high power, and wide tuning range wavelength linearly swept fiber mode-locked laser based on polygon scanning filters. An output power of 52.6 mW with 112 nm wavelength tuning range at 62.6 kHz sweeping rate has been achieved. The coherence length is long enough ... [Opt. Express 16, 14095-14105 (2008)]
      Read Full Article
    24. Speckle variance detection of microvasculature using swept-source optical coherence tomography

      Speckle variance detection of microvasculature using swept-source optical coherence tomography
      Adrian Mariampillai, Beau A. Standish, Eduardo H. Moriyama, Mamta Khurana, Nigel R. Munce, Michael K. Leung, James Jiang, Alex Cable, Brian C. Wilson, I. Alex Vitkin, Victor X. Yang. We report on imaging of microcirculation by calculating the speckle variance of optical coherence tomography (OCT) structural images acquired using a Fourier domain mode-locked swept-wavelength laser. The algorithm calculates interframe speckle variance in two-dimensional and three-dimensional OCT ... [Opt. Lett. 33, 1530-1532 (2008)]
      Read Full Article
    25. Electrostatic forward-viewing scanning probe for Doppler optical coherence tomography using a dissipative polymer catheter

      Nigel R. Munce, Adrian Mariampillai, Beau A. Standish, Mihaela Pop, Kevan J. Anderson, George Y. Liu, Tim Luk, Brian K. Courtney, Graham A. Wright, I. Alex Vitkin, Victor X. D. Yang. A novel flexible scanning optical probe is constructed with a finely etched optical fiber strung through a platinum coil in the lumen of a dissipative polymer. The packaged probe is 2.2mm in diameter with a rigid length of 6mm when using a ball lens or 12mm when scanning the fiber proximal to a ... [Opt. Lett. 33, 657-659 (2008)]
      Read Full Article
    1-25 of 25
  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. Topics in the News

    1. (25 articles) Adrian Mariampillai
    2. (23 articles) University of Toronto
    3. (23 articles) Victor X. D. Yang
    4. (21 articles) Ryerson University
    5. (13 articles) Beau A. Standish
    6. (12 articles) Kenneth K. C. Lee
    7. (10 articles) I. Alex Vitkin
    8. (8 articles) Sunnybrook Health Sciences Centre
    9. (7 articles) Ontario Cancer Institute
    10. (7 articles) Nigel R. Munce
  3. Popular Articles

  4. Picture Gallery

    Speckle variance detection of microvasculature using swept-source optical coherence tomography High-power wavelength-swept laser in Littman telescope-less polygon filter and dual-amplifier configuration for multichannel optical coherence tomography In vivo endoscopic multi-beam optical coherence tomography Doppler optical coherence tomography for interventional cardiovascular guidance: in vivo feasibility and forward-viewing probe flow phantom demonstration Simultaneous 6-channel optical coherence tomography using a high-power telescope-less polygon-based swept laser in dual amplifier configuration Optimized speckle variance OCT imaging of microvasculature Dual-core ytterbium fiber amplifier for high-power 1060 nm swept source multichannel optical coherence tomography imaging Optical coherence tomography features of neovascularization in proliferative diabetic retinopathy: a systematic review Retinal microvascular metrics in untreated essential hypertensives using optical coherence tomography angiography Optical coherence tomography angiography findings of fellow eye of proliferative macular telangiectasia type 2: Long term study Reorganization of the perifoveal microvasculature after macular hole closure assessed via optical coherence tomography angiography Optical coherence tomography angiography (OCTA) findings in Serpiginous Choroiditis