1. Articles from Julia Walther

    1-24 of 38 1 2 »
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. PhD Student Position in Optical Coherence Tomography in Biomedical Research at the TU Dresden, Germany

      PhD Student Position in Optical Coherence Tomography in Biomedical Research at the TU Dresden, Germany

      Within the scope of the junior research group “Optical Technologies in Medicine”, new methods in optical imaging are transferred into medical and clinical application. The research is focused on optical coherence tomography and other optical methods for the diagnosis of different diseases. The PHD student will join a group of medical scientists, engineers, information and natural scientists. Requirements You hold, or to be about to receive before starting the contract, a MSc degree in physics, optical engineering, electrical engineering or related areas with high interest in optical imaging. (up to 4 years after MSC degree) You have good programming skills ...

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    12. 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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    13. 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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    14. Imaging of nanoparticle-labeled stem cells using magnetomotive optical coherence tomography, laser speckle reflectometry, and light microscopy

      Imaging of nanoparticle-labeled stem cells using magnetomotive optical coherence tomography, laser speckle reflectometry, and light microscopy

      Cell transplantation and stem cell therapy are promising approaches for regenerative medicine and are of interest to researchers and clinicians worldwide. However, currently, no imaging technique that allows three-dimensional in vivo inspection of therapeutically administered cells in host tissues is available. Therefore, we investigate magnetomotive optical coherence tomography (MM-OCT) of cells labeled with magnetic particles as a potential noninvasive cell tracking method. We develop magnetomotive imaging of mesenchymal stem cells for future cell therapy monitoring. Cells were labeled with fluorescent iron oxide nanoparticles, embedded in tissue-mimicking agar scaffolds, and imaged using a microscope setup with an integrated MM-OCT probe. Magnetic ...

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    15. Visualization of dynamic boiling processes using high-speed optical coherence tomography

      Visualization of dynamic boiling processes using high-speed optical coherence tomography

      Investigating microscale nucleate boiling processes with high heat flux requires experimental visualization and quantification with high spatial resolution in the micrometer range as well as a sufficient temporal resolution. Numerous measurement techniques are employed for providing comprehensive experimental data on microscale boiling processes and other multiphase flows. In this context, optical coherence tomography (OCT) has been introduced recently for the visualization of quasistatic growing vapor bubbles in turbid fluids with a high spatial resolution. Since OCT detects backscattered light, only one optical access is necessary and OCT is feasible for measurements in turbid media, where other imaging techniques fail. Within ...

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    16. Relation of joint spectral and time domain optical coherence tomography (jSTdOCT) and phase-resolved Doppler OCT

      Relation of joint spectral and time domain optical coherence tomography (jSTdOCT) and phase-resolved Doppler OCT

      A variety of promising approaches for quantitative flow velocity measurement in OCT have been proposed in recent years. The question is: Which method gets the most precise flow velocity out of the interference signals detected. We have compared the promising joint spectral and time domain optical coherence tomography (jSTdOCT) and the commonly used phase-resolved Doppler OCT (DOCT) and describe the link between these two proven methods for OCT in the Fourier domain (FD OCT). First, we show that jSTdOCT can be significantly improved by calculating the center of gravity via an unbiased complex algorithm instead of detecting the maximum intensity ...

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    17. Magnetomotive imaging of iron oxide nanoparticles as cellular contrast agents for optical coherence tomography

      Magnetomotive imaging of iron oxide nanoparticles as cellular contrast agents for optical coherence tomography

      Recent studies in animal models provided proof-of-principle evidence for cell transplantation as a potential future therapeutic approach for retinal pathologies in humans such as Retinitis pigmentosa or age-related macular degeneration. In this case, donor cells are injected into the eye in order to protect or replace degenerating photoreceptors or retinal pigment epithelium. However, currently there is no three-dimensional imaging technique available that allows tracking of cell migration and integration into the host tissue under in vivo conditions. Therefore, we investigate about magnetomotive optical coherence tomography (OCT) of substances labeled with iron oxide nanoparticles as a potential method for noninvasive, three-dimensional ...

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    18. Endoscopic optical coherence tomography device for forward imaging with broad field of view

      Endoscopic optical coherence tomography device for forward imaging with broad field of view

      One current challenge of studying human tympanic membranes (TM) with optical coherence tomography (OCT) is the implementation of optics that avoid direct contact with the inflamed tissue. At the moment, no commercial device is available. We report an optics design for contactless forward imaging endoscopic optical coherence tomography (EOCT) with a large working distance (WD) and a broad field of view (FOV) by restricting the overall diameter of the probe to be small (3.5 mm), ensuring a sufficient numerical aperture. Our system uses a gradient-index (GRIN) relay lens and a GRIN objective lens, and executes a fan-shaped optical scanning ...

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    19. Shear flow-induced optical inhomogeneity of blood assessed in vivo and in vitro by spectral domain optical coherence tomography in the 1.3 um wavelength range

      Shear flow-induced optical inhomogeneity of blood assessed in vivo and in vitro by spectral domain optical coherence tomography in the 1.3 um wavelength range

      The optical inhomogeneity of flowing blood, which appears as a waisted double fan-shaped intensity pattern inside vessels in cross-sectional optical coherence tomography (OCT) images, was investigated for the first time. High resolution spectral domain OCT in the 1.3 μm wavelength region is used to assess this inhomogeneous intravascular backscattering of light in an in vivo mouse model and flow phantom measurements. Based on a predicted alignment of the red blood cells toward laminar shear flow, an angular modulation of the corresponding backscattering cross-section inside the vessels is assumed. In combination with the signal attenuation in depth by absorption and ...

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    20. Enhanced joint spectral and time domain optical coherence tomography for quantitative flow velocity measurement

      Enhanced joint spectral and time domain optical coherence tomography for quantitative flow velocity measurement
      Recently, a new method called joint spectral and time domain optical coherence tomography (STdOCT) for flow velocity measurement in spectral domain OCT (SD OCT) was presented. This method analyzes the detected timeresolved interference fringe spectra by using a two-dimensional fast Fourier transformation (2D FFT) to determine directly the Doppler frequency shift instead of calculating the phase difference at each depth position of adjacent A-scans. There, it was found that STdOCT is more robust for measurements with low signal to noise ratio than the classic phase-resolved Doppler OCT (DOCT) making it attractive first for imaging fast flow velocities at which a ...
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    21. Axial resolution improvement by spectral data fusion in simultaneous dual-band optical coherence tomography

      Axial resolution improvement by spectral data fusion in simultaneous dual-band optical coherence tomography

      A method for axial resolution improvement by adequate spectral data fusion of two parallel acquired disjunct wavelength bands in the 0.8 μm and 1.3 μm region in the field of simultaneous dual-band optical coherence tomography (OCT) is presented. The applied spectral domain dual-band OCT system is illuminated by a supercontinuum laser light source and allows simultaneous imaging at 800 nm and 1250 nm with free-space axial resolutions better than 4.5 μm and 7 μm, respectively, over the entire depth scan range. Each wavelength band is analyzed with an individual spectrometer at an A-scan rate of 12 kHz ...

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    22. Optical coherence tomography for imaging of subpleural alveolar structure using a Fourier domain mode locked laser

      Optical coherence tomography for imaging of subpleural alveolar structure using a Fourier domain mode locked laser

      Optical coherence tomography (OCT) is a noninvasive imaging modality generating cross sectional and volumetric images of translucent samples. In Fourier domain OCT (FD OCT), the depth profile is calculated by a fast Fourier transformation of the interference spectrum, providing speed and SNR advantage and thus making FD OCT well suitable in biomedical applications. The interference spectrum can be acquired spectrally resolved in spectral domain OCT or time-resolved in optical frequency domain imaging (OFDI). Since OCT images still suffer from motion artifacts, especially under in vivo conditions, increased depth scan rates are required. Therefor, the principle of Fourier domain mode locking ...

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    23. Endoscopic optical coherence tomography for imaging the tympanic membrane

      Endoscopic optical coherence tomography for imaging the tympanic membrane

      Optical coherence tomography (OCT) is an imaging modality that enables micrometer-scale contactless subsurface imaging of biological tissue. Endoscopy, as another imaging method, has the potential of imaging tubular organs and cavities and therefore has opened up several application areas not accessible before. The combination of OCT and endoscopy uses the advantages of both methods and consequently allows additional imaging of structures beneath surfaces inside cavities. Currently, visual investigations on the surface of the human tympanic membrane are possible but only with expert eyes. up to now, visual imaging of the outer ear up to the tympanic membrane can be carried ...

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    1-24 of 38 1 2 »
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    1. (38 articles) Dresden University of Technology
    2. (38 articles) Edmund Koch
    3. (37 articles) Julia Walther
    4. (13 articles) Peter Cimalla
    5. (11 articles) Lars Kirsten
    6. (5 articles) Henning Morawietz
    7. (5 articles) Maria Gaertner
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