1. Articles from Lars Kirsten

    1-23 of 23
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. Feasibility of non-invasive detection of engineered nanoparticles in food mimicking matrices by Optical Coherence Tomography

      Feasibility of non-invasive detection of engineered nanoparticles in food mimicking matrices by Optical Coherence Tomography

      The study was dedicated towards the detection of Engineered Nanoparticles (ENPs) by means ofOptical Coherence Tomography (OCT). Polymeric films were produced to mimic complex food matrices whereas gold nanorods (AuNRs) were embedded to act as ENPs. The straightforward coating application resulted in a sufficient film wetting, adhesion and homogenous AuNR distribution. Compared to food samples, these films are simpler and better defined. Such artefacts are therefore promising candidate materials for quality assurance and regulatory matters. The OCT investigations revealed a dependency of the measured signal intensity on the AuNR concentration in the film. The limit of detection for the setup ...

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    13. Total liquid ventilation: a new approach to improve 3D OCT image quality of alveolar structures in lung tissue

      Total liquid ventilation: a new approach to improve 3D OCT image quality of alveolar structures in lung tissue

      Little is known about mechanical processes of alveolar tissue during mechanical ventilation. Optical coherence tomography (OCT) as a three-dimensional and high-resolution imaging modality can be used to visualize subpleural alveoli during artificial ventilation. The quality of OCT images can be increased by matching the refractive index inside the alveoli to the one of tissue via liquid-filling. Thereby, scattering loss can be decreased and higher penetration depth and tissue contrast can be achieved. We show the liquid-filling of alveolar structures verified by optical coherence tomography and intravital microscopy (IVM) and the advantages of index matching for OCT imaging of subpleural alveoli ...

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    14. Vibration of the human tympanic membrane measured with OCT in a range between 0.4 kHz and 6.4 kHz on an ex vivo sample

      Vibration of the human tympanic membrane measured with OCT in a range between 0.4 kHz and 6.4 kHz on an ex vivo sample

      Vibrations of the tympanic membrane (TM) play a key role for the transmission of sound to the inner ear. Today, there exist still problems in measuring the movement of the TM and there are unresolved issues in understanding the TM and its behavior. A non-invasive and contact-free in vivo investigation of the structure and the functional behavior of the TM would be a big step forward. In the presented study, the suitability of optical coherence tomography (OCT) for measuring the oscillation patterns of the TM in the frequency range covering the range of the human speech perception should be tested ...

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    15. Four-dimensional optical coherence tomography imaging of total liquid ventilated rats

      Four-dimensional optical coherence tomography imaging of total liquid ventilated rats

      Optical coherence tomography (OCT) can be utilized for the spatially and temporally resolved visualization of alveolar tissue and its dynamics in rodent models, which allows the investigation of lung dynamics on the microscopic scale of single alveoli. The findings could provide experimental input data for numerical simulations of lung tissue mechanics and could support the development of protective ventilation strategies. Real four-dimensional OCT imaging permits the acquisition of several OCT stacks within one single ventilation cycle. Thus, the entire four-dimensional information is directly obtained. Compared to conventional virtual four-dimensional OCT imaging, where the image acquisition is extended over many ventilation ...

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    16. Optical coherence tomography as a reference method for the detection of nanoparticles in thin-film polymer matrices

      Optical coherence tomography as a reference method for the detection of nanoparticles in thin-film polymer matrices

      In food and feed production an emerging issue is the use of nanoparticles as additives to control specific properties of the products. In this context, one focus in food chemistry is the development and evaluation of measurement techniques, which could allow the detection and quantification of nanoparticles in food products. For this purpose, special noninvasive and non-destructive reference methods are required, which allow subsequent analysis with other measurement techniques. Additionally, non-invasive and fast imaging techniques are potentially appropriate for applications in the food production. Optical coherence tomography is sensitive to the backscattering of particles and is regarded as a promising ...

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    17. Investigation of the human tympanic membrane oscillation ex vivo by Doppler optical coherence tomography

      Investigation of the human tympanic membrane oscillation ex vivo by Doppler optical coherence tomography

      Investigations of the tympanic membrane (TM) can have an important impact on understanding the sound conduction in the ear and can therefore support the diagnosis and treatment of diseases in the middle ear. High-speed Doppler optical coherence tomography (OCT) has the potential to describe the oscillatory behaviour of the TM surface in a phase-sensitive manner and additionally allows acquiring a three-dimensional image of the underlying structure. With repeated sound stimuli from 0.4 kHz to 6.4 kHz, the whole TM can be set in vibration and the spatially resolved frequency response functions (FRFs) of the tympanic membrane can be ...

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    18. Feature Of The Week 8/5/12: Dresden University of Technology Uses OCT As a Tool for Microscope Investigation of Nucleated Boiling on Headed Surfaces

      Feature Of The Week 8/5/12: Dresden University of Technology Uses OCT As a Tool for Microscope Investigation of Nucleated Boiling on Headed Surfaces

      Dresden University of Technology has been very active publishing interesting articles across a wide range of technologies and applications for Optical Coherence Tomography (see Link). Recently researchers their showed an interesting non-biological non-medical applications for OCT, namely the application of OCT ininvestigating boiling phenomena. Below is a summary of their work. -Eric Swanson Boiling phenomena are an important aspect in security and efficiency for technical applications with high heat flux like nuclear reactors. This study presents optical coherence tomography (OCT) as a novel modality for three-dimensional and two-dimensional time resolved imaging of nucleate boiling on heated surfaces on a microscopic ...

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    19. 3D optical coherence tomography as new tool for microscopic investigations of nucleate boiling on heated surfaces

      3D optical coherence tomography as new tool for microscopic investigations of nucleate boiling on heated surfaces

      Boiling phenomena are an important aspect in security and efficiency for technical applications with high heat flux like nuclear reactors. This study presents optical coherence tomography (OCT) as a novel modality for three-dimensional and two-dimensional time resolved imaging of nucleate boiling on heated surfaces on a microscopic scale with high spatial (<10 μm) and temporal (>25 frames per second) resolution. Within this study, a borosilicate glass plate coated with an optically transparent and electrically conductive indium tin oxide (ITO) layer with a thickness of approximately 100 nm was used as heating surface. The combination of these two properties allows optical ...

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    20. Feature Of The Week 5/20/12: Dresden University of Technology Investigates Precision Lung Dynamics Using Four-Dimensional OCT

      Feature Of The Week 5/20/12: Dresden University of Technology Investigates Precision Lung Dynamics Using Four-Dimensional OCT

      The treatment of urgent lung diseases, such as the acute respiratory distress syndrome and the acute lung injury, requires the development of protective ventilation strategies with the help of numerical simulations. For this purpose, information about the structure of lung tissue and its dynamics is required on an alveolar level. Optical coherence tomography (OCT) can obtain high resolution cross-sectional and volumetric data of lung tissue using rodent models. Access to the lung tissue is obtained by preparing a transparent thorax window. In previous studies, OCT imaging was limited by the depth scan rate and three-dimensional information has been obtained by ...

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    21. Four-dimensional imaging of murine subpleural alveoli using high-speed optical coherence tomography

      Four-dimensional imaging of murine subpleural alveoli using high-speed optical coherence tomography

      The investigation of lung dynamics on alveolar scale is crucial for the understanding and treatment of lung diseases, such as acute lung injury and ventilator induced lung injury, and to promote the development of protective ventilation strategies. One approach to this is the establishment of numerical simulations of lung tissue mechanics where detailed knowledge about three-dimensional alveolar structure changes during the ventilation cycle is required. We suggest four-dimensional optical coherence tomography (OCT) imaging as a promising modality for visualizing the structural dynamics of single alveoli in subpleural lung tissue with high temporal resolution using a mouse model. A high-speed OCT ...

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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. Optical coherence tomography in biomedical research

      Optical coherence tomography in biomedical research
      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 biological specimens. Because of rapid improvement of the acquisition speed and axial resolution of OCT over recent years, OCT is becoming increasingly attractive for applications in biomedical research. Therefore, OCT is no longer used solely for structural investigations of biological samples but also for functional examination, making it potentially useful in bioanalytical science. The combination of in vivo structural and functional findings makes it possible to obtain thorough knowledge on basic physiological and pathological processes ...
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    1-23 of 23
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    1. (23 articles) Dresden University of Technology
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    6. (6 articles) Maria Gaertner
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    Optical coherence tomography in biomedical research Optical coherence tomography for imaging of subpleural alveolar structure using a Fourier domain mode locked laser Four-dimensional imaging of murine subpleural alveoli using high-speed optical coherence tomography Feature Of The Week 5/20/12: Dresden University of Technology Investigates Precision Lung Dynamics Using Four-Dimensional OCT 3D optical coherence tomography as new tool for microscopic investigations of nucleate boiling on heated surfaces Feature Of The Week 8/5/12: Dresden University of Technology Uses OCT As a Tool for Microscope Investigation of Nucleated Boiling on Headed Surfaces Investigation of the human tympanic membrane oscillation ex vivo by Doppler optical coherence tomography Optical coherence tomography as a reference method for the detection of nanoparticles in thin-film polymer matrices Four-dimensional optical coherence tomography imaging of total liquid ventilated rats Vibration of the human tympanic membrane measured with OCT in a range between 0.4 kHz and 6.4 kHz on an ex vivo sample Intravitreal Ranibizumab Monotherapy or Combined with Laser for Diabetic Macular Edema (OCT guided study) Prospective evaluation of drug eluting self‐apposing stent for the treatment of unprotected left main coronary artery disease: 1‐year results of the TRUNC study