1. Articles from Chia-Pin Liang

    1-23 of 23
    1. Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy in unsedated patients

      Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy in unsedated patients

      Tethered capsule endomicroscopy (TCE) is an emerging screening technology that comprehensively obtains microstructural OCT images of the gastrointestinal (GI) tract in unsedated patients. To advance clinical adoption of this imaging technique, it will be important to validate TCE images with co-localized histology, the current diagnostic gold standard. One method for co-localizing OCT images with histology is image-targeted laser marking, which has previously been implemented using a driveshaft-based, balloon OCT catheter, deployed during endoscopy. In this paper, we present a TCE device that scans and targets the imaging beam using a low-cost stepper motor that is integrated inside the capsule. In ...

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    2. Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy

      Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy

      Tethered capsule endomicroscopy (TCE) is a new method for performing comprehensive microstructural OCT imaging of gastrointestinal (GI) tract in unsedated patients in a well-tolerated and cost-effective manner. These features of TCE bestow it with significant potential to improve the screening, surveillance and management of various upper gastrointestinal diseases. To achieve clinical adoption of this imaging technique, it is important to validate it with co-registered histology, the current diagnostic gold standard. One such method for co-registering OCT images with histology is laser cautery marking, previously demonstrated using a balloon-centering OCT catheter that operates in conjunction with sedated endoscopy. With laser marking ...

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    3. Coherence gated doppler motion sensor and medical applications

      Coherence gated doppler motion sensor and medical applications

      A motion sensor applicable to medical procedures includes a source of light with a wavelength bandwidth and an optical detector. A first optical coupler terminates in a first probe tip and couples the light into the first probe tip. A second optical coupler terminates in a second probe tip and directs onto the detector scattered light returning through the second probe tip. A presentation device outputs a signal that indicates motion in a target volume of a sample in a vicinity of the probe tips based on a Doppler shift of the scattered light. The volume depends on coherence distance ...

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    4. Imaging Spinal Structures With Polarization-Sensitive Optical Coherence Tomography

      Imaging Spinal Structures With Polarization-Sensitive Optical Coherence Tomography

      Impact Statement: We investigate polarization-sensitive optical coherence tomography (PS-OCT) to obtain both intensity and polarization contrast images of in vivo and ex vivo spinal structures like subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, dura, and spinal cord in a piglet model. The PS-OCT can provide enhanced contrast characteristic structures compared to the intensity OCT; therefore it has the potential for guidance in spine interventional procedures. Abstract: We investigate polarization-sensitive optical coherence tomography (PS-OCT) to obtain both intensity and polarization contrast images of in vivo and ex vivo spinal structures like subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, dura ...

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    5. Feature of the Week 04/24/2016: μOCT Imaging Using Depth of Focus Extension by Self-Imaging Wavefront Division in a Common-Path Fiber Optic Probe

      Feature of the Week 04/24/2016: μOCT Imaging Using Depth of Focus Extension by Self-Imaging Wavefront Division in a Common-Path Fiber Optic Probe

      Optical coherence tomography (OCT) is an attractive medical modality due to its ability to acquire high-resolution, cross-sectional images inside the body using flexible, small-diameter, scanning fiber optic probes. Conventional, cross-sectional OCT imaging technologies have approximately 10-μm axial resolution and 30-μm lateral resolution, specifications that enable the visualization of microscopic architectural morphology. While this resolution is useful for many clinical applications, it is insufficient for resolving individual cells that characterize many diseases. To address this gap, a supercontinuum-laser-based, μm-resolution OCT (μOCT) system and a 500 μm-diameter, extended depth of focus single fiber optic probe for endoscopic and intravascular imaging ...

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    6. μOCT imaging using depth of focus extension by self-imaging wavefront division in a common-path fiber optic probe

      μOCT imaging using depth of focus extension by self-imaging wavefront division in a common-path fiber optic probe

      Optical coherence tomography (OCT) is an attractive medical modality due to its ability to acquire high-resolution, cross-sectional images inside the body using flexible, small-diameter, scanning fiber optic probes. Conventional, cross-sectional OCT imaging technologies have approximately 10-μm axial resolution and 30-μm lateral resolution, specifications that enable the visualization of microscopic architectural morphology. While this resolution is useful for many clinical applications, it is insufficient for resolving individual cells that characterize many diseases. To address this gap, a supercontinuum-laser-based, μm-resolution OCT (μOCT) system and a 500 μm-diameter, extended depth of focus single fiber optic probe for endoscopic and intravascular imaging ...

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    7. Quantitative single-mode fiber based PS-OCT with single input polarization state using Mueller matrix

      Quantitative single-mode fiber based PS-OCT with single input polarization state using Mueller matrix

      We present a simple but effective method to quantitatively measure the birefringence of tissue by an all single-mode fiber (SMF) based polarization-sensitive optical coherence tomography (PS-OCT) with single input polarization state. We theoretically verify that our SMF based PS-OCT system can quantify the phase retardance and optic axis orientation after a simple calibration process using a quarter wave plate (QWP). Based on the proposed method, the quantification of the phase retardance and optic axis orientation of a Berek polarization compensator and biological tissues were demonstrated.

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    8. Technology developments and biomedical applications of polarization-sensitive optical coherence tomography

      Technology developments and biomedical applications of polarization-sensitive optical coherence tomography

      Polarization-sensitive optical coherence tomography (PS-OCT) enables depth-resolved mapping of sample polarization information, such as phase-retardation and optical axis orientation, which is particularly useful when the nano-scale organization of tissue that are difficult to be observed in the intensity images of a regular optical coherence tomography (OCT). In this review, we survey two types of methods and systems of PS-OCT. The first type is PS-OCT with single input polarization state, which contain bulk optics or polarization maintaining fiber (PMF) based systems and single-mode fiber (SMF) based systems. The second type is PS-OCT with two different input polarization states, which contain SMF ...

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    9. Real-time epidural anesthesia guidance using optical coherence tomography needle probe

      Real-time epidural anesthesia guidance using optical coherence tomography needle probe

      Epidural anesthesia is one of the most widely used anesthesia methods. Due to lack of visual feedback to guide needle navigation, failure rate of epidural anesthesia is up to 20%, and the complication rate of peripheral nerve block approaches 10%, with the potential of permanent nerve damage. To address these difficulties, needle insertion under ultrasound guidance and fluoroscopy has been introduced. However, they do not provide adequate resolution and contrast to distinguish the tissue layers that the needle travels through or to specifically identify the epidural space. To improve the accuracy of epidural space identification, we developed a small hand-held ...

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    10. Real-time monitoring of hemodynamic changes in tumor vessels during photoimmunotherapy using optical coherence tomography

      Real-time monitoring of hemodynamic changes in tumor vessels during photoimmunotherapy using optical coherence tomography

      Photoimmunotherapy (PIT) is a cell-specific cancer therapy based on an armed antibody conjugate that induces rapid and highly selective cancer cell necrosis after exposure to near-infrared (NIR) light. The PIT treatment also induces the superenhanced permeability and retention effect, which allows high concentrations of nanoparticles to accumulate in the tumor bed. In our pilot studies, optical coherence tomography (OCT) reveals dramatic hemodynamic changes during PIT. We developed and applied speckle variance analysis, Doppler flow measurement, bulk motion removal, and automatic region of interest selection to quantify vessel diameter and blood velocity within tumors in vivo . OCT imaging reveals that blood ...

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    11. Optical Coherence Tomography for Neurosurgery and Cancer Research (Thesis)

      Optical Coherence Tomography for Neurosurgery and Cancer Research (Thesis)

      Optical Coherence Tomography (OCT) provides non-labeling, real-time and high resolution images, which has the potential to transform the paradigm of surgical guidance and preclinical animal studies. The design and development of OCT devices for neurosurgery guidance and novel imaging algorithms for monitoring anti-cancer therapy have been pursued in this work. A forward-imaging needle-type OCT probe was developed which can fit into minimally invasive tools (I.D. ~ 1mm), detect the at-risk blood vessels, and identify tissue micro-landmarks. This promising guidance tool improves the safety and the accuracy of needle-based procedures, which are currently performed without imaging feedback. Despite the great imaging ...

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    12. Quantitative analysis of low contrast detectability in optical coherence tomography

      Quantitative analysis of low contrast detectability in optical coherence tomography

      Optical coherence tomography (OCT) is a high resolution imaging technology that is rapidly being adopted as the standard of care for medical applications such as ocular and intravascular imaging. However, clinical translation has been hampered by the lack of standardized test methods for performance evaluation as well as consensus standards analogous to those that have been developed for established medical imaging modalities (e.g., ultrasound). In this study, we address low contrast detectability, specifically, the ability of systems to differentiate between regions exhibiting small differences in scattering coefficient. Based on standard test methods for established medical imaging modalities, we have ...

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    13. Three-dimensional printing of tissue phantoms for biophotonic imaging

      Three-dimensional printing of tissue phantoms for biophotonic imaging

      We have investigated the potential of tissue phantoms fabricated with thermosoftening- and photopolymerization-based three-dimensional (3D) printers for use in evaluation of biophotonic imaging systems. The optical properties of printed polymer samples were measured and compared to biological tissues. Phantoms with subsurface channels as small as 0.2 mm in diameter were fabricated and imaged with microscopy, x-ray microtomography, and optical coherence tomography to characterize morphology. These phantoms were then implemented to evaluate the penetration depth of a hyperspectral reflectance imaging system used in conjunction with a near-infrared contrast agent. Results indicated that 3D printing may provide a suitable platform for ...

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    14. Quantitative assessment of biophotonic imaging system performance with phantoms fabricated by rapid prototyping

      Quantitative assessment of biophotonic imaging system performance with phantoms fabricated by rapid prototyping

      In biophotonic imaging, turbid phantoms that are low-cost, biologically-relevant, and durable are desired for standardized performance assessment. Such phantoms often contain inclusions of varying depths and sizes in order to quantify key image quality characteristics such as penetration depth, sensitivity and contrast detectability. The emerging technique of rapid prototyping with three-dimensional (3D) printers provides a potentially revolutionary way to fabricate these structures. Towards this goal, we have characterized the optical properties and morphology of phantoms fabricated by two 3D printing approaches: thermosoftening and photopolymerization. Material optical properties were measured by spectrophotometry while the morphology of phantoms incorporating 0.2-1.0 ...

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    15. Feature Of The Week 5/5/13: University of Maryland Reports Interesting Results on OCT Needle Probe Used In Conjunction with Magnetic Resonance Imaging for Precision Surgical Procedures

      Feature Of The Week 5/5/13: University of Maryland Reports Interesting Results on OCT Needle Probe Used In Conjunction with Magnetic Resonance Imaging for Precision Surgical Procedures

      We develop a novel platform based on a tele-operated robot to perform high-resolution optical coherence tomography (OCT) imaging under continuous large field-of-view magnetic resonance imaging (MRI) guidance. Intra-operative MRI (iMRI) is a promising guidance tool for high-precision surgery, but it may not have sufficient resolution or contrast to visualize certain small targets. To address these limitations, we develop an MRI-compatible OCT needle probe, which is capable of providing microscale tissue architecture in conjunction with macroscale MRI tissue morphology in real time. Coregistered MRI/OCT images on ex vivo chicken breast and human brain tissues demonstrate that the complementary imaging scales ...

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    16. Concurrent multiscale imaging with magnetic resonance imaging and optical coherence tomography

      Concurrent multiscale imaging with magnetic resonance imaging and optical coherence tomography

      We develop a novel platform based on a tele-operated robot to perform high-resolution optical coherence tomography (OCT) imaging under continuous large field-of-view magnetic resonance imaging (MRI) guidance. Intra-operative MRI (iMRI) is a promising guidance tool for high-precision surgery, but it may not have sufficient resolution or contrast to visualize certain small targets. To address these limitations, we develop an MRI-compatible OCT needle probe, which is capable of providing microscale tissue architecture in conjunction with macroscale MRI tissue morphology in real time. Coregistered MRI/OCT images on ex vivo chicken breast and human brain tissues demonstrate that the complementary imaging scales ...

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    17. Coherence-gated Doppler: a fiber sensor for precise localization of blood flow

      Coherence-gated Doppler: a fiber sensor for precise localization of blood flow

      Miniature optical sensors that can detect blood vessels in front of advancing instruments will significantly benefit many interventional procedures. Towards this end, we developed a thin and flexible coherence-gated Doppler (CGD) fiber probe (O.D. = 0.125 mm) that can be integrated with minimally-invasive tools to provide real-time audio feedback of blood flow at precise locations in front of the probe. Coherence-gated Doppler (CGD) is a hybrid technology with features of laser Doppler flowmetry (LDF) and Doppler optical coherence tomography (DOCT). Because of its confocal optical design and coherence-gating capabilities, CGD provides higher spatial resolution than LDF. And compared to ...

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    18. Endoscopic Microscopy Using Optical Coherence Tomography

      Endoscopic Microscopy Using Optical Coherence Tomography

      Optical coherence tomography (OCT) can perform high-speed, micron-level high resolution imaging of tissue microstructures in vivo and in real time and can function as a type of optical biopsy to visualize the structural and functional alterations associated with various diseases. The advances in endoscopic OCT and optical coherence microscopy (OCM) provide an exciting avenue for many promising clinical applications with the potential of enhancing diagnostic capabilities and treatment efficacies. In this review paper, we first review the basic principles for time- and Fourierdomain OCT. We then survey the various endoscopic OCT technologies followed by the review of several representative clinical ...

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    19. Review of advanced imaging techniques

      Review of advanced imaging techniques

      Pathology informatics encompasses digital imaging and related applications. Several specialized microscopy techniques have emerged which permit the acquisition of digital images ("optical biopsies") at high resolution. Coupled with fiber-optic and micro-optic components, some of these imaging techniques (e.g., optical coherence tomography) are now integrated with a wide range of imaging devices such as endoscopes, laparoscopes, catheters, and needles that enable imaging inside the body. These advanced imaging modalities have exciting diagnostic potential and introduce new opportunities in pathology. Therefore, it is important that pathology informaticists understand these advanced imaging techniques and the impact they have on pathology. This paper ...

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    20. Characterizing the point spread function of retinal OCT devices with a model eye-based phantom

      Characterizing the point spread function of retinal OCT devices with a model eye-based phantom

      We have designed, fabricated, and tested a nanoparticle-embedded phantom (NEP) incorporated into a model eye in order to characterize the point spread function (PSF) of retinal optical coherence tomography (OCT) devices in three dimensions under realistic imaging conditions. The NEP comprises a sparse distribution of highly backscattering silica-gold nanoshells embedded in a transparent UV-curing epoxy. The commercially-available model eye replicates the key optical structures and focusing power of the human eye. We imaged the model eye-NEP combination with a research-grade spectral domain OCT system designed for in vivo retinal imaging and quantified the lateral and axial PSF dimensions across the ...

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    21. Towards a discretely actuated steerable cannula for diagnostic and therapeutic procedures

      Towards a discretely actuated steerable cannula for diagnostic and therapeutic procedures

      We have designed, developed, and evaluated the performance of a multi-degree-of-freedom discretely actuated steerable cannula with shape-memory alloy (SMA) actuators. This will enable us to deliver diagnostic as well as therapeutic devices to the target location through the hollow inner core of the cannula. We propose to use SMAs to generate bending forces due to its small size and high power density. We annealed the SMA wires through a customized training process in an arc shape and mounted them at discrete locations on the outer surface of the cannula to enable joint motion. A pulse-width modulation (PWM)-based control scheme ...

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    22. Congratulations to Chia-Pin Liang From the University of Maryland a Winner of a 2012 Student Travel Grant Award

      Congratulations to Chia-Pin Liang From the University of Maryland a Winner of a 2012 Student Travel Grant Award
      Chia-Pin Liang from the University of Maryland is one of four winners of the OCT News 2012 student travel grant awards (see prior announcement Here). Below is a summary of his work. Stereotactic procedures that require insertion of needle-based instruments into the brain serve important roles in a variety of neurosurgical interventions such as biopsy, catheterization, and electrode placement. The laceration of blood vessels in the path of the advancing needle can result in stroke and even death and is perhaps the most worried complication. Also, the brain may shift during surgery because of cerebrospinal fluid (CSF) leakage so that ...
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    23. A forward-imaging needle-type OCT probe for image guided stereotactic procedures

      A forward-imaging needle-type OCT probe for image guided stereotactic procedures
      A forward-imaging needle-type optical coherence tomography (OCT) probe with Doppler OCT (DOCT) capability has the potential to solve critical challenges in interventional procedures. A case in point is stereotactic neurosurgery where probes are advanced into the brain based on predetermined coordinates. Laceration of blood vessels in front of the advancing probe is an unavoidable complication with current methods. Moreover, cerebrospinal fluid (CSF) leakage during surgery can shift the brain rendering the predetermined coordinates unreliable. In order to address these challenges, we developed a forward-imaging OCT probe (740 μm O.D.) using a gradient-index (GRIN) rod lens that can provide real-time ...
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    1-23 of 23
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    1. (23 articles) Chia-Pin Liang
    2. (19 articles) University of Maryland
    3. (19 articles) Yu Chen
    4. (4 articles) Harvard University
    5. (4 articles) Massachusetts General Hospital
    6. (4 articles) Guillermo J. Tearney
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    A forward-imaging needle-type OCT probe for image guided stereotactic procedures Congratulations to Chia-Pin Liang From the University of Maryland a Winner of a 2012 Student Travel Grant Award Towards a discretely actuated steerable cannula for diagnostic and therapeutic procedures Characterizing the point spread function of retinal OCT devices with a model eye-based phantom Review of advanced imaging techniques Coherence-gated Doppler: a fiber sensor for precise localization of blood flow Concurrent multiscale imaging with magnetic resonance imaging and optical coherence tomography Feature Of The Week 5/5/13: University of Maryland Reports Interesting Results on OCT Needle Probe Used In Conjunction with Magnetic Resonance Imaging for Precision Surgical Procedures μOCT imaging using depth of focus extension by self-imaging wavefront division in a common-path fiber optic probe Feature of the Week 04/24/2016: μOCT Imaging Using Depth of Focus Extension by Self-Imaging Wavefront Division in a Common-Path Fiber Optic Probe Long-Term Arterial Remodeling After Bioresorbable Scaffold Implantation 4-Year Follow-up of Quantitative Coronary Angiography, Histology and Optical Coherence Tomography Visualization of Bacterial Colonization and Cellular Layers in a Gut-on-a-Chip System Using Optical Coherence Tomography