1. Articles from Beau A. Standish

    1-25 of 25
    1. Quantifying temperature changes in tissue-mimicking fluid phantoms using optical coherence tomography and envelope statistics

      Quantifying temperature changes in tissue-mimicking fluid phantoms using optical coherence tomography and envelope statistics

      Several therapies make use of a hypo or hyperthermia tissue environment to induce cell death in both benign and malignant tumors. Current progression in optical technologies, such as optical coherence tomography (OCT) and fiber Bragg gratings (FBG) sensors, could potentially provide viable information to explore the response of tissue when these temperature induced treatments are implemented. Studies were conducted with tissue-mimicking phantoms fabricated with polystyrene microspheres and glycerin to observe any relationship between the pixel intensities of the OCT images and their concurring envelope statistics. OCT images of the monitored region of interest were taken at 5°C intervals from ...

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    2. Analyzing effects of temperature on tissue equivalent phantoms using fiber Bragg gratings and optical coherence tomography

      Analyzing effects of temperature on tissue equivalent phantoms using fiber Bragg gratings and optical coherence tomography

      There exist a multitude of therapeutic options for the treatment of both benign and malignant tumors, where several of these options induce temperature changes in the tissue from several degrees centigrade to temperatures that ablate the region of interest (ROI). Recent advances in optical imaging technologies, namely optical coherence tomography (OCT) and Fiber Bragg Gratings (FBG), may provide the necessary hardware/software components to both monitor and quantify the direct biological response to temperature-mediated cancer therapies. Preliminary research has been conducted to identify and analyze the trends in temperature measurements from FBG's placed within phantoms that mimic the optical ...

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    3. Blood flow velocity measurement by endovascular Doppler optical coherence tomography

      Blood flow velocity measurement by endovascular Doppler optical coherence tomography

      Blood flow velocity and volumetric flow measurements are important parameters for assessment of the severity of stenosis and the outcome of interventional therapy. However, feasibility of intravascular flow measurement using a rotational catheter based phase resolved Doppler optical coherence tomography (DOCT) is difficult. Motion artefacts induced by the rotating optical imaging catheter, and the radially dependent noise background of measured Doppler signals are the main challenges encountered. In this study, a custom-made data acquisition system and developed algorithms to remove non-uniform rotational distortion (NURD) induced phase shift artefact by tracking the phase shift observed on catheter sheath. The flow velocity ...

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    4. 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 ...

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    5. Speckle reduction of endovascular optical coherence tomography using a generalized divergence measure

      Speckle reduction of endovascular optical coherence tomography using a generalized divergence measure

      ndovascular optical coherence tomography (EV-OCT) is an emerging intravascular imaging technique for observing blood vessel walls. Fluctuating speckle noise, especially during rapid pull-back, can severely degrade the visibility of morphological structures. Moreover, the speckle pattern varies in different parts of the image due to beam divergence and is further complicated by interpolation through the coordinate transformation necessary for displaying the rotary scanning images, challenging the use of frequency domain analysis. In this study, a computationally efficient method using a generalized divergence regularization procedure is presented to suppress speckle noise in EV-OCT images. Results show substantial smoothing of the grainy appearance ...

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    6. 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 ...

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    7. Intraoperative handheld optical coherence tomography forward-viewing probe: physical performance and preliminary animal imaging

      Intraoperative handheld optical coherence tomography forward-viewing probe: physical performance and preliminary animal imaging

      A prototype intraoperative hand-held optical coherence tomography (OCT) imaging probe was developed to provide micron resolution cross-sectional images of subsurface tissue during open surgery. This new ergonomic probe was designed based on electrostatically driven optical fibers, and packaged into a catheter probe in the form factor of clinically accepted Bayonet shaped neurosurgical probes. Optical properties of the probe were measured to have a ~20 μm spot size, 5 mm working distance and 4 mm field of view. Feasibility of this probe for structural and Doppler shift imaging was tested on porcine femoral blood vessel imaging.

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    8. Comprehensive data visualization for high resolution endovascular carotid arterial wall imaging

      Comprehensive data visualization for high resolution endovascular carotid arterial wall imaging

      Carotid angioplasty and stenting is a minimally invasive endovascular procedure that may benefit from in vivo high resolution imaging for monitoring the physical placement of the stent and potential complications. The purpose of this pilot study was to evaluate the ability of optical coherence tomography to construct high resolution 2D and 3D images of stenting in porcine carotid artery. Four Yorkshire pigs were anaesthetized and catheterized. A state-of-the-art optical coherence tomography (OCT) system and an automated injector were used to obtain both healthy and stented porcine carotid artery images. Data obtained were then processed for visualization. The state-of-the-art OCT system ...

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    9. Noninvasive in vivo structural and vascular imaging of human oral tissues with spectral domain optical coherence tomography

      Noninvasive in vivo structural and vascular imaging of human oral tissues with spectral domain optical coherence tomography

      A spectral domain optical coherence tomography (SD-OCT) system and an oral imaging probe have been developed to visualize the microstructural morphology and microvasculature in the human oral cavity. Structural OCT images of ex vivo pig oral tissues with the histology of the same sites were acquired and compared for correlations. Structural in vivo OCT images of healthy human tissue as well as a pathologic site (ulcer) were obtained and analyzed based on the results of the ex vivo pig study, drawing on the similarity between human and swine oral tissues. In vivo Doppler and speckle variance OCT images of the ...

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    10. Feasibility and methodology of optical coherence tomography imaging of human intracranial aneurysms: ex vivo pilot study

      Feasibility and methodology of optical coherence tomography imaging of human intracranial aneurysms: ex vivo pilot study

      Rupture of intracranial aneurysm is a common cause of subarachnoid hemorrhage. An aneurysm may undergo microscopic morphological changes or remodeling of the vessel wall prior to rupture, which could potentially be imaged. In this study we present methods of tissue sample preparation of intracranial aneurysms and correlation between optical coherence tomography imaging and routine histology. OCT has a potential future in the assessment of microscopic features of aneurysms, which may correlate to the risk of rupture.

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    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 ...

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    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 ...

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    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 ...
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    14. 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.
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    15. 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 ...
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    16. Developing dual core ytterbium doped fiber ring laser in Fourier domain mode locked operation for swept-source optical coherence tomography

      Developing dual core ytterbium doped fiber ring laser in Fourier domain mode locked operation for swept-source optical coherence tomography
      We demonstrate high efficiency and wide bandwidth gain in a Ytterbium doped fiber amplifier. The highpowered amplifier has potential applications for use with a swept-source fiber ring laser in multi-channel optical coherence tomography (OCT) system. The ring cavity design includes a 976nm pumped dual core Yb doped fiber as the gain medium, where a rotating polygon mirror is used as a wavelength-sweeping filter for this source. The amplified spontaneous emission (ASE) had a spectral bandwidth of 1037-1145nm at -60dBm, where a tunable lasing bandwidth of the ring cavity ranged from 1057-1115nm. The highest output power, for both the ASE and ...
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    17. Cascaded Raman fiber laser in Fourier domain mode lock operation

      Cascaded Raman fiber laser in Fourier domain mode lock operation
      In this study, a cascaded Raman fiber laser in Fourier domain mode lock operation (FDML) is presented. This laser utilizes a Ytterbium doped twin core pump laser source at 1109 nm. The pump light is directed to a cascaded Raman cavity, which consists of multiple cascaded fiber Bragg grating pairs and 3.86 km of dispersion compensation fiber, which provides Raman gain. The output wavelength of a cascaded Raman laser is determined by the Stoke’s shift (≈ 60 to 70 nm in optical fiber) and the pump laser wavelength. The power build up in the cascaded Raman cavity and shift ...
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    18. 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 ...
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    19. Wavelength-swept spectral and pulse shaping utilizing hybrid Fourier domain modelocking by fiber optical parametric and erbium-doped fiber amplifiers

      Wavelength-swept spectral and pulse shaping utilizing hybrid Fourier domain modelocking by fiber optical parametric and erbium-doped fiber amplifiers

      We report the first Fourier domain modelocked (FDML) laser constructed using optical parametric amplifier (OPA) in conjunction with an erbium-doped fiber amplifier (EDFA), centered at ~1555nm, to the best of our knowledge. We utilize a one-pump OPA and a C-band EDFA in serial configuration with a tunable Fabry-Perot interferometer to generate a hybrid FDML spectrum. Results demonstrate a substantially better spectral shape, output power and stability than individual configurations, with decreased sensitivity to polarization changes. We believe this technique has the potential to enable several amplifiers to complement individual deficiencies resulting in improved spectral shapes and power generation for imaging ...

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    20. 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 ...
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    21. 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 ...
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    22. 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 ...
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    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)]
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    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)]
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    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)]
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    1-25 of 25
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    1. (24 articles) Beau A. Standish
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    Speckle variance detection of microvasculature using swept-source optical coherence tomography In vivo endoscopic multi-beam optical coherence tomography Wavelength-swept spectral and pulse shaping utilizing hybrid Fourier domain modelocking by fiber optical parametric and erbium-doped fiber amplifiers Doppler optical coherence tomography for interventional cardiovascular guidance: in vivo feasibility and forward-viewing probe flow phantom demonstration Developing dual core ytterbium doped fiber ring laser in Fourier domain mode locked operation for swept-source optical coherence tomography Cascaded Raman fiber laser in Fourier domain mode lock operation 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 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