1. Articles from martin villiger

    1-24 of 51 1 2 3 »
    1. Measuring collagen injury depth for burn severity determination using polarization sensitive optical coherence tomography

      Measuring collagen injury depth for burn severity determination using polarization sensitive optical coherence tomography

      Determining the optimal treatment course for a dermatologic burn wound requires knowledge of the wound's severity, as quantified by the depth of thermal damage. In current clinical practice, burn depth is inferred based exclusively on superficial visual assessment, a method which is subject to substantial error rates in the classification of partial thickness (second degree) burns. Here, we present methods for direct, quantitative determination of the depth extent of injury to the dermal collagen matrix using polarization-sensitive optical coherence tomography (PS-OCT). By visualizing the depth-dependence of the degree of polarization of light in the tissue, rather than cumulative retardation ...

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    2. Three-dimensional opto-thermo-mechanical model for predicting photo-thermal optical coherence tomography responses in multilayer geometries

      Three-dimensional opto-thermo-mechanical model for predicting photo-thermal optical coherence tomography responses in multilayer geometries

      Photothermal optical coherence tomography (PT-OCT) is a functional extension of OCT with the ability to generate qualitative maps of molecular absorptions co-registered with the micron-resolution structural tomograms of OCT. Obtaining refined insight into chemical information from PT-OCT images, however, requires solid understanding of the multifactorial physics behind generation of PT-OCT signals and their dependence on system and sample parameters. Such understanding is needed to decouple the various physical effects involved in the PT-OCT signal to obtain more accurate insight into sample composition. In this work, we propose an analytical model that considers the opto-thermo-mechanical properties of multi-layered samples in 3-D ...

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    3. Transient-mode photothermal optical coherence tomography

      Transient-mode photothermal optical coherence tomography

      Photothermal optical coherence tomography (PT-OCT) is an emerging extension of OCT, which forms images based on both scattering and absorption of light. The speed of PT-OCT, however, has been limited by the necessity for lock-in detection with extensive temporal sampling of the sample’s PT response. Here, we demonstrate transient-mode PT-OCT (TM-PT-OCT), which increases the effective A-line rate by orders of magnitude from 10–100 Hz to 1.5–7.5 kHz, by interrogating the sample’s transient thermal response to a single diode laser pulse. Functional imaging of moving samples with TM-PT-OCT at video rate is also presented. This ...

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    4. Spectral- and Polarization-Dependent Scattering of Gold Nanobipyramids for Exogenous Contrast in Optical Coherence Tomography

      Spectral- and Polarization-Dependent Scattering of Gold Nanobipyramids for Exogenous Contrast in Optical Coherence Tomography

      Polarization-sensitive optical coherence tomography (PS-OCT) reveals the subsurface microstructure of biological tissue and provides information regarding the polarization state of light backscattered from tissue. Complementing OCT's structural signal with molecular imaging requires strategies to simultaneously detect multiple exogenous contrast agents with high specificity in tissue. Specific detection of molecular probes enables the parallel visualization of physiological, cellular, and molecular processes. Here we demonstrate that, by combining PS-OCT and spectral contrast (SC)-OCT measurements, we can distinguish signatures of different gold nanobipyramids (GNBPs) in lymphatic vessels from the surrounding tissue and blood vessels in live mouse models. This technique could ...

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    5. Rapid non-destructive volumetric tumor yield assessment in fresh lung core needle biopsies using polarization sensitive optical coherence tomography

      Rapid non-destructive volumetric tumor yield assessment in fresh lung core needle biopsies using polarization sensitive optical coherence tomography

      Adequate tumor yield in core-needle biopsy (CNB) specimens is essential in lung cancer for accurate histological diagnosis, molecular testing for therapeutic decision-making, and tumor biobanking for research. Insufficient tumor sampling in CNB is common, primarily due to inadvertent sampling of tumor-associated fibrosis or atelectatic lung, leading to repeat procedures and delayed diagnosis. Currently, there is no method for rapid, non-destructive intraprocedural assessment of CNBs. Polarization-sensitive optical coherence tomography (PS-OCT) is a high-resolution, volumetric imaging technique that has the potential to meet this clinical need. PS-OCT detects endogenous tissue properties, including birefringence from collagen, and degree of polarization uniformity (DOPU) indicative ...

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    6. Effects of lipid composition on photothermal optical coherence tomography signals

      Effects of lipid composition on photothermal optical coherence tomography signals

      Significance: Photothermal optical coherence tomography (PT-OCT) has the promise to offer structural images coregistered with chemical composition information, which can offer a significant impact in early detection of diseases such as atherosclerosis. Aim: We take the first step in understanding the relation between PT-OCT signals and the endogenous tissue composition by considering the interplay between the opto-thermo-physical properties of tissue as a function of its lipid composition and the ensuing effects on the PT-OCT signals. Approach: Multiparameter theoretical estimates for PT-OCT signal as a function of composition in a two-component lipid–water model are derived and discussed. Experimental data from ...

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    7. Linear-in-wavenumber actively-mode-locked wavelength-swept laser

      Linear-in-wavenumber actively-mode-locked wavelength-swept laser

      We report on an akinetic actively-mode-locked wavelength-swept laser (ASL) with a sweep that is highly linear in wavenumber. By tailoring the drive waveform of the intracavity modulator, the wavenumber sweep was further linearized to enable high fidelity frequency-domain interferometric ranging without resampling of the acquired data. Used for catheter-based optical coherence tomography, the ASL showed comparable imaging performance to a state-of-the-art polygon-based wavelength-swept source at a matching sweep rate of 103.6 kHz, a duty cycle of 95%, and a bandwidth of 100 nm, centered at 1330 nm.

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    8. Intravascular Polarimetry: Clinical Translation and Future Applications of Catheter-Based Polarization Sensitive Optical Frequency Domain Imaging

      Intravascular Polarimetry: Clinical Translation and Future Applications of Catheter-Based Polarization Sensitive Optical Frequency Domain Imaging

      Optical coherence tomography (OCT) and optical frequency domain imaging (OFDI) visualize the coronary artery wall and plaque morphology in great detail. The advent of these high-resolution intracoronary imaging modalities has propelled our understanding of coronary atherosclerosis and provided enhanced guidance for percutaneous coronary intervention. Yet, the lack of contrast between distinct tissue types and plaque compositions impedes further elucidation of the complex mechanisms that contribute to acute coronary syndrome (ACS) and hinders the prospective identification of plaques susceptible to rupture. Intravascular polarimetry with polarization-sensitive OFDI measures polarization properties of the coronary arterial wall using conventional intravascular imaging catheters. The quantitative ...

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    9. Influence of tissue fixation on depth-resolved birefringence of oral cavity tissue samples

      Influence of tissue fixation on depth-resolved birefringence of oral cavity tissue samples

      Significance: To advance our understanding of the contrast observed when imaging with polarization-sensitive optical coherence tomography (PS-OCT) and its correlation with oral cancerous pathologies, a detailed comparison with histology provided via ex vivo fixed tissue is required. The effects of tissue fixation, however, on such polarization-based contrast have not yet been investigated. Aim: A study was performed to assess the impact of tissue fixation on depth-resolved (i.e., local) birefringence measured with PS-OCT. Approach: A PS-OCT system based on depth-encoded polarization multiplexing and polarization-diverse detection was used to measure the Jones matrix of a sample. A wide variety of ex ...

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    10. In vivo imaging of the depth-resolved optic axis of birefringence in human skin

      In vivo imaging of the depth-resolved optic axis of birefringence in human skin

      Recent progress has enabled the reconstruction of the local (i.e., depth-resolved) optic axis (OAx) of biological tissue from measurements made with polarization-sensitive optical coherence tomography (PS-OCT). Here we demonstrate local OAx imaging in healthy human skin in vivo . The images reveal dense, weaving patterns that are imperceptible in OCT intensity tomograms or conventional PS-OCT metrics and that suggest a mesh-like tissue organization, consistent with the morphology of dermal collagen. Using co-registered polarization-sensitive optical coherence microscopy, we furthermore investigated the impact of spatial resolution on the recovered OAx patterns and confirmed their consistency. OAx orientation as a contrast mechanism merits ...

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    11. Forward multiple scattering dominates speckle decorrelation in whole-blood flowmetry using optical coherence tomography

      Forward multiple scattering dominates speckle decorrelation in whole-blood flowmetry using optical coherence tomography

      Quantitative blood flow measurements using optical coherence tomography (OCT) have a wide potential range of medical research and clinical applications. Flowmetry based on the temporal dynamics of the OCT signal may have the ability to measure three-dimensional flow profiles regardless of the flow direction. State-of-the-art models describing the OCT signal temporal statistics are based on dynamic light scattering (DLS), a model which is inherently limited to single scattering regimes. DLS methods continue to be applied to OCT despite the knowledge that red blood cells produce strong forward multiple scattering. Here, we postulate that forward multiple scattering is the primary mechanism ...

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    12. Vectorial birefringence imaging by optical coherence microscopy for assessing fibrillar microstructures in the cornea and limbus

      Vectorial birefringence imaging by optical coherence microscopy for assessing fibrillar microstructures in the cornea and limbus

      The organization of fibrillar tissue on the micrometer scale carries direct implications for health and disease but remains difficult to assess in vivo . Polarization-sensitive optical coherence tomography measures birefringence, which relates to the microscopic arrangement of fibrillar tissue components. Here, we demonstrate a critical improvement in leveraging this contrast mechanism by employing the improved spatial resolution of focus-extended optical coherence microscopy (1.4 µm axially in air and 1.6 µm laterally, over more than 70 µm depth of field). Vectorial birefringence imaging of sheep cornea ex vivo reveals its lamellar organization into thin sections with distinct local optic axis ...

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    13. Intravascular Polarimetry in Patients With Coronary Artery Disease

      Intravascular Polarimetry in Patients With Coronary Artery Disease

      Objectives The aims of this first-in-human pilot study of intravascular polarimetry were to investigate polarization properties of coronary plaques in patients and to examine the relationship of these features with established structural characteristics available to conventional optical frequency domain imaging (OFDI) and with clinical presentation. Background Polarization-sensitive OFDI measures birefringence and depolarization of tissue together with conventional cross-sectional optical frequency domain images of subsurface microstructure. Methods Thirty patients undergoing polarization-sensitive OFDI (acute coronary syndrome, n = 12; stable angina pectoris, n = 18) participated in this study. Three hundred forty-two cross-sectional images evenly distributed along all imaged coronary arteries were classified into ...

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    14. Intravascular Polarimetry for Tissue Characterization of Coronary Atherosclerosis

      Intravascular Polarimetry for Tissue Characterization of Coronary Atherosclerosis

      The microscopic tissue structure and organization influence the polarization of light. Intravascular polarimetry leverages this compelling intrinsic contrast mechanism by using polarization-sensitive optical frequency domain imaging to measure the polarization properties of the coronary arterial wall. Tissues rich in collagen and smooth muscle cells appear birefringent, while the presence of lipid causes depolarization, offering quantitative metrics related to the presence of important components of coronary atherosclerosis. Here, we review the basic principles, the interpretation of polarization signatures, and first clinical investigations of intravascular polarimetry and discuss how this extension of contemporary intravascular imaging may advance our knowledge and improve clinical ...

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    15. Constrained polarization evolution simplifies depth-resolved retardation measurements with polarization-sensitive optical coherence tomography

      Constrained polarization evolution simplifies depth-resolved retardation measurements with polarization-sensitive optical coherence tomography

      We observed that the polarization state of light after round-trip propagation through a birefringent medium frequently aligns with the employed input polarization state ‘mirrored’ by the horizontal plane of the Poincaré sphere. We explored the predisposition for this mirror state and evidence that it constrains the evolution of polarization states as a function of the round-trip depth into weakly scattering birefringent samples, as measured with polarization-sensitive optical coherence tomography (PS-OCT). Combined with spectral variations in the polarization state transmitted through system components, we demonstrate how this constraint enables measurement of depth-resolved birefringence using only a single input polarization state, which ...

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    16. Distinguishing Tumor from Associated Fibrosis to Increase Diagnostic Biopsy Yield with Polarization-Sensitive Optical Coherence Tomography

      Distinguishing Tumor from Associated Fibrosis to Increase Diagnostic Biopsy Yield with Polarization-Sensitive Optical Coherence Tomography

      Purpose: With recent advancements in personalized medicine, biopsies must contain sufficient tumor for histologic diagnosis and molecular testing. However, inadvertent biopsy of tumor-associated fibrosis compromises tumor yield, resulting in delayed diagnoses and/or repeat procedures when additional tumor is needed. The ability to differentiate tumor from fibrosis intraprocedurally during biopsy could significantly increase tumor yield. Polarization-sensitive optical coherence tomography (PS-OCT) is an imaging modality that is endoscope- and/or needle-compatible, and provides large volumetric views of tissue microstructure with high resolution (∼10 μm) while simultaneously measuring birefringence of organized tissues such as collagen. We aim to determine whether PS-OCT can ...

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    17. Depth-resolved birefringence imaging of collagen fiber organization in the human oral mucosa in vivo

      Depth-resolved birefringence imaging of collagen fiber organization in the human oral mucosa in vivo

      Stromal collagen organization has been identified as a potential prognostic indicator in a variety of cancers and other diseases accompanied by fibrosis. Changes in the connective tissue are increasingly considered for grading dysplasia and progress of oral squamous cell carcinoma, investigated mainly ex vivo by histopathology. In this study, polarization-sensitive optical coherence tomography (PS-OCT) with local phase retardation imaging is used for the first time to visualize depth-resolved (i.e., local) birefringence of healthy human oral mucosa in vivo . Depth-resolved birefringence is shown to reveal the expected local collagen organization. To demonstrate proof-of-principle, 3D image stacks were acquired at labial ...

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    18. Balloon catheter-based radiofrequency ablation monitoring in porcine esophagus using optical coherence tomography

      Balloon catheter-based radiofrequency ablation monitoring in porcine esophagus using optical coherence tomography

      We present a microscopic image guidance platform for radiofrequency ablation (RFA) using a clinical balloon-catheter-based optical coherence tomography (OCT) system, currently used in the surveillance of Barrett’s esophagus patients. Our integrated thermal therapy delivery and monitoring platform consists of a flexible, customized bipolar RFA electrode array designed for use with a clinical balloon OCT catheter and a processing algorithm to accurately map the thermal coagulation process. Non-uniform rotation distortion was corrected using a feature tracking-based technique, which enables robust, frame-to-frame analysis of the temporal fluctuation of the complex OCT signal. With proper noise calibration, precise delineation of the thermal ...

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    19. Robust reconstruction of local optic axis orientation with fiber-based polarization-sensitive optical coherence tomography

      Robust reconstruction of local optic axis orientation with fiber-based polarization-sensitive optical coherence tomography

      It is challenging to recover local optic axis orientation from samples probed with fiber-based polarization-sensitive optical coherence tomography (PS-OCT). In addition to the effect of preceding tissue layers, the transmission through fiber and system elements, and imperfect system alignment, need to be compensated. Here, we present a method to retrieve the required correction factors from measurements with depth-multiplexed PS-OCT, which accurately measures the full Jones matrix. The correction considers both retardation and diattenuation and is applied in the wavenumber domain, preserving the axial resolution of the system. The robustness of the method is validated by measuring a birefringence phantom with ...

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    20. Optic axis mapping with catheter-based polarization-sensitive optical coherence tomography

      Optic axis mapping with catheter-based polarization-sensitive optical coherence tomography

      Birefringence offers an intrinsic contrast mechanism related to the microstructure and arrangement of fibrillary tissue components. Here we present a reconstruction strategy to recover not only the scalar amount of birefringence, but also its optic axis orientation as a function of depth in tissue from measurements with catheter-based polarization-sensitive optical coherence tomography. A polarization symmetry constraint, intrinsic to imaging in the backscatter direction, facilitates the required compensation for wavelength-dependent transmission through the system elements, the rotating catheter, and overlying tissue layers. Applied to the intravascular imaging of coronary atherosclerosis in human patients, the optic axis affords refined interpretation of plaque ...

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    21. Quantitative depolarization measurements for fiber‐based polarization‐sensitive optical frequency domain imaging of the retinal pigment epithelium

      Quantitative depolarization measurements for fiber‐based polarization‐sensitive optical frequency domain imaging of the retinal pigment epithelium

      A full quantitative evaluation of the depolarization of light may serve to assess concentrations of depolarizing particles in the retinal pigment epithelium and to investigate their role in retinal diseases in the human eye. Optical coherence tomography (OCT) and optical frequency domain imaging (OFDI) use spatial incoherent averaging to compute depolarization. Depolarization depends on accurate measurements of the polarization states at the receiver but also on the polarization state incident upon and within the tissue. Neglecting this dependence can result in artifacts and renders depolarization measurements vulnerable to birefringence in the system and in the sample. In this work, we ...

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    22. Robust wavenumber and dispersion calibration for Fourier-domain optical coherence tomography

      Robust wavenumber and dispersion calibration for Fourier-domain optical coherence tomography

      Many Fourier-domain optical coherence tomography (FD-OCT) systems sample the interference fringes with a non-uniform wavenumber ( k ) interval, introducing a chirp to the signal that depends on the path length difference underlying each fringe. A dispersion imbalance between sample and reference arms also generates a chirp in the fringe signal which, in contrast, is independent of depth. Fringe interpolation to obtain a signal linear in k and compensate dispersion imbalance is critical to achieving bandwidth-limited axial resolution. In this work, we propose an optimization-based algorithm to perform robust and automated calibration of FD-OCT systems, recovering both the interpolation function and the ...

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    23. Prediction of scar size in rats six months after burns based on early post injury polarization-sensitive optical frequency domain imaging

      Prediction of scar size in rats six months after burns based on early post injury polarization-sensitive optical frequency domain imaging

      Hypertrophic scars remain a major clinical problem in the rehabilitation of burn survivors and lead to physical, aesthetic, functional, psychological, and social stresses. Prediction of healing outcome and scar formation is critical for deciding on the best treatment plan. Both subjective and objective scales have been devised to assess scar severity. Whereas scales of the first type preclude cross-comparison between observers, those of the second type are based on imaging modalities that either lack the ability to image individual layers of the scar or only provide very limited fields of view. To overcome these deficiencies, this work aimed at developing ...

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    1-24 of 51 1 2 3 »
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