1. Articles from Edmund Koch

    1-24 of 87 1 2 3 4 »
    1. Endoscopic Optical Coherence Tomography for Evaluation of Success of Tympanoplasty

      Endoscopic Optical Coherence Tomography for Evaluation of Success of Tympanoplasty

      Objective: After tympanoplasty , it is often challenging to differentiate between different causes of a remaining air bone gap (ABG). Optical coherence tomography (OCT) offers a new approach for combined morphologic and functional measurements of the tympanic membrane and adjacent parts of the middle ear. Thus, it provides valuable diagnostic information in patients with a reduced sound transfer after middle ear surgery. Patient and intervention: A patient with history of tympanoplasty and a persistent ABG was investigated with endoscopic OCT before revision surgery. Main Outcome Measures: The oscillation behavior and the thickness of the reconstructed tympanic membrane was determined. The oscillation ...

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    2. Device and system for doppler optical coherence tomography (OCT) of the human middle ear

      Device and system for doppler optical coherence tomography (OCT) of the human middle ear

      A device for Doppler optical coherence tomography (Doppler OCT), preferably of the human middle ear, is proposed. The device has an endoscope unit for at least partial insertion into the auditory canal. A sound source, a sound receiver, and OCT optics are integrated in the endoscope unit.

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    3. Correlation between Lesion Progression and Depolarization Assessed by Polarization-Sensitive Optical Coherence Tomography

      Correlation between Lesion Progression and Depolarization Assessed by Polarization-Sensitive Optical Coherence Tomography

      The detection of early stages of caries is still one of the major challenges in preservative dentistry. Since it is known from polarized light microscopy (PLM) that intrinsic enamel birefringence is affected by demineralization, polarization-sensitive optical coherence tomography (PSOCT) could facilitate the noninvasive detection and assessment of early carious lesions. The present study aims to correlate enamel lesion progression and depolarization measurements based on PSOCT in an artificial demineralization model. A total of 18 enamel slabs were prepared from bovine incisor teeth and demineralized in an acetic buffer solution for up to 49 days. The degree of polarization (DOP)—indicating ...

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    4. 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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    5. Endoscopic optical coherence tomography with wide field-of-view for the morphological and functional assessment of the human tympanic membrane

      Endoscopic optical coherence tomography with wide field-of-view for the morphological and functional assessment of the human tympanic membrane

      An endoscopic optical coherence tomography (OCT) system with a wide field-of-view of 8 mm is presented, which combines the image capability of endoscopic imaging at the middle ear with the advantages of functional OCT imaging, allowing a morphological and functional assessment of the human tympanic membrane. The endoscopic tube has a diameter of 3.5 mm and contains gradient-index optics for simultaneous forward-viewing OCT and video endoscopy. The endoscope allows the three-dimensional visualization of nearly the entire tympanic membrane. In addition, the oscillation of the tympanic membrane is measured spatially resolved and in the frequency range between 500 Hz and ...

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    6. Visualization of interfacial adhesive defects at dental restorations with spectral domain and polarization sensitive optical coherence tomography

      Visualization of interfacial adhesive defects at dental restorations with spectral domain and polarization sensitive optical coherence tomography

      Restoration loss based on interfacial adhesive defects and associated caries at the restoration margin are the main causes for invasive replacement of dental restorations. Assessment of the interfacial quality based on clinical inspection and radiographic examination is often difficult and not reliable. In this work, we present spectral domain optical coherence tomography (SDOCT) and polarization sensitive optical coherence tomography (PSOCT) for the evaluation of tooth-composite bond failure. Imaging of two composite restorations at the occlusal surface are presented using intensity-based images obtained by SDOCT and PSOCT based degree of polarization uniformity (DOPU). Both modalities revealed several defects beneath the surface ...

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    7. Optical Coherence Tomography for NDE (Book Chapter)

      Optical Coherence Tomography for NDE (Book Chapter)

      Optical coherence tomography (OCT) is a noninvasive, high-resolution, interferometric imaging modality using near-infrared light to acquire cross sections and three-dimensional images of the subsurface microstructure of samples. Because of the rapid enhancement of OCT with respect to acquisition speed and axial resolution over the past years, OCT is becoming more and more attractive for applications in nondestructive testing and evaluation. In this chapter, a brief introduction to the technique and the instrumentation is first given, followed by an overview of application of OCT in NDE reported so far.

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    8. Multimodal imaging of lung tissue dynamics in mechanically ventilated rats with optical coherence tomography and intravital microscopy

      Multimodal imaging of lung tissue dynamics in mechanically ventilated rats with optical coherence tomography and intravital microscopy

      The understanding of alveolar mechanics is an essential step towards new and more protective ventilation strategies which are of dare need for the treatment of diseases of lung tissue and the airways. Such ailments become a major task for medical care and health care systems in modern industrial countries in the future. Besides the obvious importance as life-saving intervention, the mechanical strain and processes on the level of gas exchange are still insufficiently understood. Therefore, it is of great interest to characterize lung tissue and tissue dynamics during artificial ventilation at the alveolar level. 4D Optical coherence tomography (OCT) in ...

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    9. 4D optical coherence tomography for imaging aortic valve dynamics ex vivo

      4D optical coherence tomography for imaging aortic valve dynamics ex vivo

      The mechanical components of the heart, especially the valves, are enormously stressed during lifetime and undergo different pathophysiological tissue transformations, which affect cardiac output and in consequence living comfort of affected patients. Calcific aortic valve stenosis (AVS) is the most common valve disease in modern industrial countries but the pathogenesis and progression of this disease is still unknown. Therefore, animal models, especially mouse models, are a powerfull tool to investigate this disease in more detail with high resolution imaging techniques like optical coherence tomography and video microscopy. A custom-made pump was used for artificial stimulation of aortic valves ex vivo ...

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    10. In vivo imaging in the oral cavity by endoscopic optical coherence tomography

      In vivo imaging in the oral cavity by endoscopic optical coherence tomography

      The common way to diagnose hard and soft tissue irregularities in the oral cavity is initially the visual inspection by an experienced dentist followed by further medical examinations, such as radiological imaging and/or histopathological investigation. For the diagnosis of oral hard and soft tissues, the detection of early transformations is mostly hampered by poor visual access, low specificity of the diagnosis techniques, and/or limited feasibility of frequent screenings. Therefore, optical noninvasive diagnosis of oral tissue is promising to improve the accuracy of oral screening. Considering this demand, a rigid handheld endoscopic scanner was developed for optical coherence tomography ...

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    11. Detection of carious lesions utilizing depolarization imaging by polarization sensitive optical coherence tomography

      Detection of carious lesions utilizing depolarization imaging by polarization sensitive optical coherence tomography

      As dental caries is one of the most common diseases, the early and noninvasive detection of carious lesions plays an important role in public health care. Optical coherence tomography (OCT) with its ability of depth-resolved, high-resolution, noninvasive, fast imaging has been previously recognized as a promising tool in dentistry. Additionally, polarization sensitive imaging provides quantitative measures on the birefringent tissue properties and can be utilized for imaging dental tissue, especially enamel and dentin. By imaging three exemplary tooth samples ex vivo with proximal white spot, brown spot, and cavity, we show that the combination of polarization sensitive OCT and the ...

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    12. In vivo imaging of human oral hard and soft tissues by polarization-sensitive optical coherence tomography

      In vivo imaging of human oral hard and soft tissues by polarization-sensitive optical coherence tomography

      Since optical coherence tomography (OCT) provides three-dimensional high-resolution images of biological tissue, the benefit of polarization contrast in the field of dentistry is highlighted in this study. Polarization-sensitive OCT (PS OCT) with phase-sensitive recording is used for imaging dental and mucosal tissues in the human oral cavity in vivo . An enhanced polarization contrast of oral structures is reached by analyzing the signals of the co- and crosspolarized channels of the swept source PS OCT system quantitatively with respect to reflectivity, retardation, optic axis orientation, and depolarization. The calculation of these polarization parameters enables a high tissue-specific contrast imaging for the ...

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    13. Advanced analysis of domain walls in Mg doped LiNbO3 crystals with high resolution OCT

      Advanced analysis of domain walls in Mg doped LiNbO3 crystals with high resolution OCT

      The structure of domain walls (DW) in ferroelectric media is of great interest as this material is used for frequency doublers and other applications. We show that the structure of the DWs can nicely be visualized by high resolution optical coherence tomography (OCT). While the high group refractive index of lithium niobate allows a resolution much better than 1 µm, the large dispersion can blur the image and has to be compensated. Therefore, we developed an adaptive dispersion compensation algorithm based on maximizing the intensity of the DWs. By measuring a group of DWs, the mean period of the DWs ...

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    14. Improved Imaging of Magnetically Labeled Cells Using Rotational Magnetomotive Optical Coherence Tomography

      Improved Imaging of Magnetically Labeled Cells Using Rotational Magnetomotive Optical Coherence Tomography

      Abstract In this paper, we present a reliable and robust method for magnetomotive optical coherence tomography (MM-OCT) imaging of single cells labeled with iron oxide particles. This method employs modulated longitudinal and transverse magnetic fields to evoke alignment and rotation of anisotropic magnetic structures in the sample volume. Experimental evidence suggests that magnetic particles assemble themselves in elongated chains when exposed to a permanent magnetic field. Magnetomotion in the intracellular space was detected and visualized by means of 3D OCT as well as laser speckle reflectometry as a 2D reference imaging method. Our experiments on mesenchymal stem cells embedded in ...

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    15. Flow Measurement by Lateral Resonant Doppler Optical Coherence Tomography in the Spectral Domain

      Flow Measurement by Lateral Resonant Doppler Optical Coherence Tomography in the Spectral Domain

      In spectral domain optical coherence tomography (SD-OCT), any transverse motion component of a detected obliquely moving sample results in a nonlinear relationship between the Doppler phase shift and the axial sample velocity restricting phase-resolved Doppler OCT (PR-DOCT). The size of the deviation from the linear relation depends on the amount of the transverse velocity component, given by the Doppler angle, and the height of the absolute sample velocity. Especially for very small Doppler angles between the horizontal and flow direction, and high flow velocities, the detected Doppler phase shift approaches a limiting value, making an unambiguous measurement of the axial ...

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    16. Optical Coherence Tomography (OCT) for Time-Resolved Imaging of Alveolar Dynamics in Mechanically Ventilated Rats

      Optical Coherence Tomography (OCT) for Time-Resolved Imaging of Alveolar Dynamics in Mechanically Ventilated Rats

      Though artificial ventilation is an essential life-saving treatment, the mechanical behavior of lung tissue at the alveolar level is still unknown. Therefore, we need to understand the tissue response during artificial ventilation at this microscale in order to develop new and more protective ventilation methods. Optical coherence tomography (OCT) combined with intravital microscopy (IVM) is a promising tool for visualizing lung tissue dynamics with a high spatial and temporal resolution in uninterruptedly ventilated rats. We present a measurement setup using a custom-made animal ventilator and a gating technique for data acquisition of time-resolved sequences.

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    17. Impact of a detector dead time in phase-resolved Doppler analysis using spectral domain optical coherence tomography

      Impact of a detector dead time in phase-resolved Doppler analysis using spectral domain optical coherence tomography

      For any oblique sample movement containing a transverse velocity component, the commonly used linear relationship between the phase shift and the axial velocity component is erroneous for spectrometer-based optical coherence tomography (spectral domain OCT, SD-OCT). We recently proposed a new Doppler model that assumes a continuous integration of the photocurrent. In this research, we extend the model for detectors with a shutter control by taking detector dead time into account. We present the new relation between phase shift and oblique sample displacement as well as the correlation of the phases of consecutive depth scans, in dependency on the detector dead ...

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    18. Doppler optical coherence tomography as a promising tool for detecting fluid in the human middle ear

      Doppler optical coherence tomography as a promising tool for detecting fluid in the human middle ear

      The treatment of otitis media requires classifying the effusion in the tympanic cavity for choosing appropriate therapeutic strategies. Otoscopic examination of the middle ear depends on the expertise of the physician and is often hampered in case of inflammatory alterations of the tympanic membrane. In otologic research, optical coherence tomography is an innovative non-invasive imaging technique utilized for visualizing the tympanic membrane. This ex vivo study presents the possibility of OCT and Doppler-OCT for the detection of effusions in the tympanic cavity. Structural OCT imaging allows the direct visualization of scattering fluids behind the tympanic membrane. In addition, the measurement ...

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    19. Improved non-invasive Optical Coherence Tomography detection of different engineered nanoparticles in food-mimicking matrices

      Improved non-invasive Optical Coherence Tomography detection of different engineered nanoparticles in food-mimicking matrices

      Food industry and regulators require fast and reliable analytical methods for quality control. This especially counts for the detection of engineered nanomaterials (ENMs) in food products. Respective EU regulation is in force, but the development of appropriate methods is still underway. This paper updates the scope of Optical Coherence Tomography (OCT) for ENM/food matrix analysis. A range of nanomaterials and composites – Au@SiO 2 , Ag, Ag@SiO 2 and SiO 2 – in a simplified food matrix was investigated. The earlier finding of linear dependencies between concentration in the dispersion and light responses could be reproduced. Being able to analyse ...

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    20. NADPH oxidase 4 protects against development of endothelial dysfunction and atherosclerosis in LDL receptor deficient mice

      NADPH oxidase 4 protects against development of endothelial dysfunction and atherosclerosis in LDL receptor deficient mice

      Aims Endothelial dysfunction is an early step in the development of atherosclerosis. Increased formation of superoxide anions by NADPH oxidase Nox1, 2, and 5 reduces nitric oxide availability and can promote endothelial dysfunction. In contrast, recent evidence supports a vasoprotective role of H 2 O 2 produced by main endothelial isoform Nox4. Therefore, we analysed the impact of genetic deletion of Nox4 on endothelial dysfunction and atherosclerosis in the low-density lipoprotein receptor (Ldlr) knockout model. Methods and results Ex vivo analysis of endothelial function by Mulvany myograph showed impaired endothelial function in thoracic aorta of Nox4 −/− /Ldlr −/− mice. Further progression ...

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    21. Imaging of aortic valve dynamics in 4D OCT New insights into murine aortic valve diseases

      Imaging of aortic valve dynamics in 4D OCT  New insights into murine aortic valve diseases

      The mechanical components of the heart, especially the valves and leaflets, are enormous stressed during lifetime. Therefore, those structures undergo different pathophysiological tissue transformations which affect cardiac output and in consequence living comfort of affected patients. These changes may lead to calcific aortic valve stenosis (AVS), the major heart valve disease in humans. The knowledge about changes of the dynamic behaviour during the course of this disease and the possibility of early stage diagnosis is of particular interest and could lead to the development of new treatment strategies and drug based options of prevention or therapy. 4D optical coherence tomography ...

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    22. Optimal processing of Doppler signals in OCT

      Optimal processing of Doppler signals in OCT

      Besides structural imaging, OCT can be used to estimate axial velocities of the sample resolved in depth by Doppler processing. In Fourier domain OCT (FD-OCT), this is accomplished by measuring the phase difference (i.e. phase shift) between timely separated A-scans at the same depth. In most cases, these data are disturbed by noise caused by intrinsic noise of the OCT system, specified by the SNR, and decorrelation noise caused by the transversal movement of the optical beam relative to the sample. Since the first use of Doppler methods in OCT, many methods to reduce the phase shift noise by ...

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    23. Imaging the tympanic membrane oscillation ex vivo with Doppler optical coherence tomography during simulated Eustachian catarrh

      Imaging the tympanic membrane oscillation ex vivo with Doppler optical coherence tomography during simulated Eustachian catarrh

      Recently, optical coherence tomography (OCT) was utilized in multiple studies for structural and functional imaging of the middle ear and the tympanic membrane. Since Doppler OCT allows both, the spatially resolved measurement of the tympanic membrane oscillation and high-resolution imaging, it is regarded as a promising tool for future in vivo applications. In this study, Doppler OCT is utilized for the visualization of the tympanic membrane oscillation in temporal bones with simulated Eustachian catarrh, which was realized by generating a depression in the tympanic cavity. The transfer function, meaning the oscillation amplitude normalized to the applied sound pressure, is measured ...

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    24. 4D optical coherence tomography of aortic valve dynamics in a murine mouse model ex vivo

      4D optical coherence tomography of aortic valve dynamics in a murine mouse model ex vivo

      The heart and its mechanical components, especially the heart valves and leaflets, are under enormous strain during lifetime. Like all highly stressed materials, also these biological components undergo fatigue and signs of wear, which impinge upon cardiac output and in the end on health and living comfort of affected patients. Thereby pathophysiological changes of the aortic valve leading to calcific aortic valve stenosis (AVS) as most frequent heart valve disease in humans are of particular interest. The knowledge about changes of the dynamic behavior during the course of this disease and the possibility of early stage diagnosis could lead to ...

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    1-24 of 87 1 2 3 4 »
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  2. Topics in the News

    1. (87 articles) Dresden University of Technology
    2. (87 articles) Edmund Koch
    3. (37 articles) Julia Walther
    4. (27 articles) Sven Meissner
    5. (26 articles) Lars Kirsten
    6. (26 articles) Peter Cimalla
    7. (23 articles) Maria Gaertner
    8. (7 articles) Henning Morawietz
    9. (3 articles) University of Toronto
    10. (3 articles) Alexander Kr├╝ger
    11. (1 articles) Institute of Applied Physics
    12. (1 articles) Medical University of Vienna
    13. (1 articles) Kyungpook National University
    14. (1 articles) Singapore Eye Research Institute
    15. (1 articles) University of Western Australia
    16. (1 articles) Stefan G. Sacu
    17. (1 articles) Brendan F. Kennedy
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    Simultaneous dual-band optical coherence tomography in the spectral domain for high resolution in vivo imaging Minimal invasive localization of the germinal disc in ovo for subsequent chicken sexing using optical coherence tomography Combining optical coherence tomography with fluorescence microscopy: a closer look into tissue Signal power decrease due to fringe washout as an extension of the limited Doppler flow measurement range in spectral domain optical coherence tomography Optical coherence tomography in biomedical research Investigation of alveolar tissue deformations using OCT combined with fluorescence microscopy Full-range space-division multiplexing optical coherence tomography angiography Measuring 3D Optic Nerve Head Deformations using Digital Volume Correlation of in vivo Optical Coherence Tomography Data (Thesis) Optical coherence tomography for characterization of nanocomposite materials (Thesis) In Vivo Corneal Microstructural Changes in Herpetic Stromal Keratitis: A Spectral-Domain Optical Coherence Tomography Analysis Non-invasive optical screening of Streptococcus Pneumonia based inflammatory changes of the tympanic membrane and mastoid mucosa in guinea pig otitis media using optical coherence tomography Visual function tests including the role of optical coherence tomography in neurofibromatosis