1. Articles from Kanwarpal Singh

    1-20 of 20
    1. Depth encoded input polarisation independent swept source cross-polarised optical coherence tomography probe

      Depth encoded input polarisation independent swept source cross-polarised optical coherence tomography probe

      Within the last decades, several studies have been published that prove the benefit of polarisation sensitive optical coherence (psOCT) tomography for the field of biomedical diagnostics. However, polarisation sensitive imaging typically requires careful control of the polarisation state of the input illumination, which leads to bulky and delicate systems. While psOCT provides quantitative information, it is mostly sufficient to analyse the images qualitatively in the field of biomedical diagnostics. Therefore, a reduced form of this technique, cross-polarised optical coherence tomography (cpOCT), moves into the focus of interest that serves to visualise the birefringence properties of a sample. Despite the low ...

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    2. Portable Optical Coherence Elastography System With Flexible and Phase Stable Common Path Optical Fiber Probe

      Portable Optical Coherence Elastography System With Flexible and Phase Stable Common Path Optical Fiber Probe

      Biomechanical properties drive the functioning of cells and tissue. Measurement of such properties in the clinic is quite challenging, however. Optical coherence elastography is an emerging technique in this field that can measure the biomechanical properties of the tissue. Unfortunately, such systems have been limited to benchtop configuration with limited clinical applications. A truly portable system with a flexible probe that could probe different sample sites with ease is still missing. In this work, we report a portable optical coherence elastography system based on a flexible common path optical fiber probe. The common path approach allows us to reduce the ...

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    3. Feasibility and safety of tethered capsule endomicroscopy in patients with Barrett’s esophagus in a multi-center study

      Feasibility and safety of tethered capsule endomicroscopy in patients with Barrett’s esophagus in a multi-center study

      Background & Aims Tethered capsule endomicroscopy (TCE) involves swallowing small tethered pill that implements optical coherence tomography (OCT) imaging, procuring high resolution images of the whole esophagus. Here, we demonstrate and evaluate the feasibility and safety of TCE and a portable OCT imaging system in patients with Barrett’s esophagus (BE) in a multi-center (5-site) clinical study. Methods Untreated patients with BE as per endoscopic biopsy diagnosis were eligible to participate in the study. TCE procedures were performed in unsedated patients by either doctors or nurses. After the capsule was swallowed, the device continuously obtained 10-μm-resolution cross-sectional images as it ...

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    4. Novel input polarisation independent endoscopic cross polarised optical coherence tomography probe

      Novel input polarisation independent endoscopic cross polarised optical coherence tomography probe

      Lead by the original idea to perform noninvasive optical biopsies of various tissue, optical coherence tomography found numerous medical applications within the last two decades. The interference based imaging technique opens the possibility to visualise subcellular morphology up to an imaging depth of 3 mm and up to micron level axial and lateral resolution. The birefringence properties of the tissue are visualised with enhanced contrast using polarisation sensitive or cross polarised optical coherence tomography techniques. Although, it requires strict control over the polarisation states, resulting in several polarisation controlling elements. In this work, we propose a novel input‐polarisaion independent ...

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    5. Input polarization-independent polarization-sensitive optical coherence tomography using a depolarizer

      Input polarization-independent polarization-sensitive optical coherence tomography using a depolarizer

      Polarization-sensitive optical coherence tomography is gaining attention because of its ability to diagnose certain pathological conditions at an early stage. The majority of polarization-sensitive optical coherence tomography systems require a polarization controller and a polarizer to obtain the optimal polarization state of the light at the sample. Such systems are prone to misalignment since any movement of the optical fiber normally coupled to the light source will change the polarization state of the incident beam. We propose and demonstrate an input polarization-independent polarization-sensitive optical coherence tomography system using a depolarizer that works for any input polarization state of the light ...

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    6. Swept source cross-polarized optical coherence tomography for any input polarized light

      Swept source cross-polarized optical coherence tomography for any input polarized light

      Cross polarized optical coherence tomography offers enhanced contrast in certain pathological conditions. Traditional cross-polarized optical coherence tomography systems require a defined input polarization and thus require several polarization controlling elements increasing the overall complexity of the system. Our proposed system requires a single quarter wave plate as a polarization controller thus simplifying the system significantly. Majority of Cross-polarized optical coherence tomography systems are spectrometer based which suffers from slow speed and low signal to noise ratio. In this work, we present a swept source based cross-polarized optical coherence tomography system that works for any input polarization state. The system was ...

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    7. All fiber polarization insensitive detection for spectrometer based optical coherence tomography using optical switch

      All fiber polarization insensitive detection for spectrometer based optical coherence tomography using optical switch

      Polarization dependent image artifacts are common in optical coherence tomography imaging. Polarization insensitive detection scheme for swept source based optical coherence tomography systems is well established but is yet to be demonstrated for all fiber spectrometer-based Fourier domain optical coherence tomography systems. In this work, we present an all fiber polarization insensitive detection scheme for spectrometer based optical coherence tomography systems. Images from chicken breast muscle tissue were acquired to demonstrate the effectiveness of this scheme for the conventional Fourier domain optical coherence tomography system.

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    8. Low cost scalable monolithic common path probe design for the application in endoscopic optical coherence tomography

      Low cost scalable monolithic common path probe design for the application in endoscopic optical coherence tomography

      Endoscopic optical coherence tomography is an interference based imaging technique which due to its micron level resolution ability found several applications in medical diagnostics. However, the standard image performance suffers from artefacts caused by dispersion imbalance and polarisation mismatches between reference and sample arm. Such artefacts can be minimised with the use of a special class of probes called common path probes where the reference surface is placed in the vicinity of the sample. Previously reported common path probes suffered from a compromise between sensitivity and resolution. In most cases, proposed probes were not scalable for industrial applications and required ...

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    9. Imaging the Human Prostate Gland Using 1-μm-Resolution Optical Coherence Tomography

      Imaging the Human Prostate Gland Using 1-μm-Resolution Optical Coherence Tomography

      Context.— The accuracy of needle biopsy for the detection of prostate cancer is limited by well-known sampling errors. Thus, there is an unmet need for a microscopic screening tool that can screen large regions of the prostate comprehensively for cancer. Previous prostate imaging by optical coherence tomography (OCT) has had insufficient resolution for imaging cellular features related to prostate cancer. We have recently developed micro-optical coherence tomography (μOCT) that generates depth-resolved tissue images at a high frame rate with an isotropic resolution of 1 μm. Objective.— To demonstrate that optical images obtained with μOCT provide cellular-level contrast in prostate specimens ...

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    10. 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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    11. Imaging the Human Prostate Gland Using 1-μm-Resolution Optical Coherence Tomography

      Imaging the Human Prostate Gland Using 1-μm-Resolution Optical Coherence Tomography

      Context.— The accuracy of needle biopsy for the detection of prostate cancer is limited by well-known sampling errors. Thus, there is an unmet need for a microscopic screening tool that can screen large regions of the prostate comprehensively for cancer. Previous prostate imaging by optical coherence tomography (OCT) have had insufficient resolution for imaging cellular features related to prostate cancer. We have recently developed micro-optical coherence tomography (μOCT) that generates depth-resolved tissue images at a high frame rate with an isotropic resolution of 1 μm. Objective.— To demonstrate that optical images obtained with μOCT provide cellular-level contrast in prostate specimens ...

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    12. 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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    13. Contrast enhancement of microscopic birefringent crystals using polarization sensitive micro-optical coherence tomography

      Contrast enhancement of microscopic birefringent crystals using polarization sensitive micro-optical coherence tomography

      Background: Birefringent crystals such as cholesterol and monosodium urate have recently been identified as possible pharmacologic targets for the treatment of coronary artery disease. The size of these crystals can be very small (on the order of 1 µm), making them difficult to identify. To image these microscopic crystals and enhance contrast, we modified existing micro optical coherence tomography system so that it was capable of obtaining polarization-sensitive images (PS-µOCT). A spectrometer-based PS-µOCT system was developed using a 270 nm wide broadband light source centered at 765 nm. Light was polarized using a polarizer and coupled to a ...

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    14. Estimation and compensation of dispersion for high-resolution optical coherence tomography system

      Estimation and compensation of dispersion for high-resolution optical coherence tomography system

      Balanced reference-sample arm dispersion is critical in optical coherence tomography systems in order to attain images with the highest axial resolution. Here, an experimental method for the estimation and correction of dispersion in an optical coherence tomography system is presented. The system dispersion was computed from two optical coherence tomography images of the reference mirror that were symmetrically placed around the zero delay point. The method was tested using a broad bandwidth spectral domain optical coherence tomography system, compensating for the dispersion caused by a 3-mm-thick fused silica flat placed in the sample arm. Using our method, dispersion compensation was ...

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    15. In-line optical fiber metallic mirror reflector for monolithic common path optical coherence tomography probes

      In-line optical fiber metallic mirror reflector for monolithic common path optical coherence tomography probes

      Background and Objectives Endoscopic optical coherence tomography probes suffer from various artifacts due to dispersion imbalance and polarization mismatch between reference and sample arm light. Such artifacts can be minimized using a common path approach. In this work, we demonstrate a miniaturized common path probe for optical coherence tomography using an inline fiber mirror. Materials and Methods A common path optical fiber probe suitable for performing high-resolution endoscopic optical coherence tomography imaging was developed. To achieve common path functionality, an inline fiber mirror was fabricated using a thin gold layer. A commercially available swept source engine was used to test ...

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    16. Astigmatism corrected common path probe for optical coherence tomography

      Astigmatism corrected common path probe for optical coherence tomography

      Background and Objectives Optical coherence tomography (OCT) catheters for intraluminal imaging are subject to various artifacts due to reference-sample arm dispersion imbalances and sample arm beam astigmatism. The goal of this work was to develop a probe that minimizes such artifacts. Materials and Methods Our probe was fabricated using a single mode fiber at the tip of which a glass spacer and graded index objective lens were spliced to achieve the desired focal distance. The signal was reflected using a curved reflector to correct for astigmatism caused by the thin, protective, transparent sheath that surrounds the optics. The probe design ...

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    17. In vivo imaging of airway cilia and mucus clearance with micro-optical coherence tomography

      In vivo imaging of airway cilia and mucus clearance with micro-optical coherence tomography

      We have designed and fabricated a 4 mm diameter rigid endoscopic probe to obtain high resolution micro-optical coherence tomography (µOCT) images from the tracheal epithelium of living swine. Our common-path fiber-optic probe used gradient-index focusing optics, a selectively coated prism reflector to implement a circular-obscuration apodization for depth-of-focus enhancement, and a common-path reference arm and an ultra-broadbrand supercontinuum laser to achieve high axial resolution. Benchtop characterization demonstrated lateral and axial resolutions of 3.4 μm and 1.7 μm, respectively (in tissue). Mechanical standoff rails flanking the imaging window allowed the epithelial surface to be maintained in focus without disrupting ...

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    18. 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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    19. 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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    20. Common Path Side Viewing Monolithic Ball Lens Probe for Optical Coherence Tomography

      Common Path Side Viewing Monolithic Ball Lens Probe for Optical Coherence Tomography

      Common path probes are highly desirable for optical coherence tomography as they reduce system complexity and cost by eliminating the need of dispersion compensation and polarization controlling optics. In this work, we demonstrate a monolithic ball lens based, common path, side viewing probe that is suitable for Fourier domain optical coherence tomography. The probe design parameters were simulated in Zemax modeling software and the simulated performance parameters were compared with experimental results. We characterized the performance of the probe by measuring its collection efficiency, resolution, and sensitivity. Our results demonstrated that with a source input power of 25 mW, we ...

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    1-20 of 20
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  2. Topics in the News

    1. (14 articles) Harvard University
    2. (14 articles) Massachusetts General Hospital
    3. (4 articles) University of Erlangen
    4. (1 articles) UC Irvine
    5. (1 articles) Columbia University
    6. (1 articles) University of Alabama
    7. (1 articles) Michalina J. Góra
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    Common Path Side Viewing Monolithic Ball Lens Probe for Optical Coherence Tomography 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 In vivo imaging of airway cilia and mucus clearance with micro-optical coherence tomography Astigmatism corrected common path probe for optical coherence tomography Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy Imaging the Human Prostate Gland Using 1-μm-Resolution Optical Coherence Tomography Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy in unsedated patients Imaging the Human Prostate Gland Using 1-μm-Resolution Optical Coherence Tomography Low cost scalable monolithic common path probe design for the application in endoscopic optical coherence tomography Post-Doctoral and Graduate Student Research Positions at the University of Illinois Urbana-Champaign Multiscale correlation of microvascular changes on optical coherence tomography angiography with retinal sensitivity in diabetic retinopathy