1. Articles from Nils C. Gerhardt

    1-12 of 12
    1. Brain tissue analysis using texture features based on optical coherence tomography images

      Brain tissue analysis using texture features based on optical coherence tomography images

      Brain tissue differentiation is highly demanded in neurosurgeries, i.e. tumor resection. Exact navigation during the surgery is essential in order to guarantee best life quality afterwards. So far, no suitable method has been found that perfectly covers this demands. With optical coherence tomography (OCT), fast three dimensional images can be obtained in vivo and contactless with a resolution of 1-15 μm. With these specifications OCT is a promising tool to support neurosurgeries. Here, we investigate ex vivo samples of meningioma, healthy white and healthy gray matter in a preliminary study towards in vivo brain tumor removal assistance. Raw OCT ...

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    2. Automated differentiation between meningioma and healthy brain tissue based on optical coherence tomography ex vivo images using texture features

      Automated differentiation between meningioma and healthy brain tissue based on optical coherence tomography ex vivo images using texture features

      Brain tissue analysis is highly desired in neurosurgery, such as tumor resection. To guarantee best life quality afterward, exact navigation within the brain during the surgery is essential. So far, no method has been established that perfectly fulfills this need. Optical coherence tomography (OCT) is a promising three-dimensional imaging tool to support neurosurgical resections. We perform a preliminary study toward in vivo brain tumor removal assistance by investigating meningioma, healthy white, and healthy gray matter. For that purpose, we utilized a commercially available OCT device (Thorlabs Callisto) and measured eight samples of meningioma, three samples of healthy white, and two ...

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    3. Feature Of The Week 07/24/2017: Spectral Domain Optical Coherence Tomography for Non-Destructive Testing of Protection Coatings on Metal Substrates

      Feature Of The Week 07/24/2017: Spectral Domain Optical Coherence Tomography for Non-Destructive Testing of Protection Coatings on Metal Substrates

      Industrial monuments and other artefacts of vanishing industries have to be preserved as cultural heritage. For example, in Germany next year the public subsidy for the mining industry will end and with this the active mining will end as well. The Deutsches Bergbau-Museum in Bochum as one of the largest of its kind and as a research institution of the Leibnitz association is committed to preserve the cultural heritage of the mining industry. Thus it is facing the huge task to conserve a lot of mining industry objects in their actual authentic appearance, ranging from small tools like hammers to ...

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    4. Spectroscopic optical coherence tomography for ex vivo brain tumor analysis

      Spectroscopic optical coherence tomography for ex vivo brain tumor analysis

      For neurosurgeries precise tumor resection is essential for the subsequent recovery of the patients since nearby healthy tissue that may be harmed has a huge impact on the life quality after the surgery. However, so far no satisfying methodology has been established to assist the surgeon during surgery to distinguish between healthy and tumor tissue. Optical Coherence Tomography (OCT) potentially enables non-contact in vivo image acquisition at penetration depths of 1-2 mm with a resolution of approximately 1-15 μm. To analyze the potential of OCT for distinction between brain tumors and healthy tissue, we used a commercially available Thorlabs Callisto ...

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    5. Multiwavelength phase unwrapping and aberration correction using depth filtered digital holography

      Multiwavelength phase unwrapping and aberration correction using depth filtered digital holography

      In this Letter, we present a new approach to processing data from a standard spectral domain optical coherence tomography (OCT) system using depth filtered digital holography (DFDH). Intensity-based OCT processing has an axial resolution of the order of a few micrometers. When the phase information is used to obtain optical path length differences, subwavelength accuracy can be achieved, but this limits the resolvable step heights to half of the wavelength of the system. Thus there is a metrology gap between phase- and intensity-based methods. Our concept addresses this metrology gap by combining DFHD with multiwavelength phase unwrapping. Additionally, the measurements ...

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    6. Comparison of different metrics for analysis and visualization in spectroscopic optical coherence tomography

      Comparison of different metrics for analysis and visualization in spectroscopic optical coherence tomography

      Spectroscopic Optical Coherence Tomography (S-OCT) extracts depth resolved spectra that are inherently available from OCT signals. The back scattered spectra contain useful functional information regarding the sample, since the light is altered by wavelength dependent absorption and scattering caused by chromophores and structures of the sample. Two aspects dominate the performance of S-OCT: (1) the spectral analysis processing method used to obtain the spatially-resolved spectroscopic information and (2) the metrics used to visualize and interpret relevant sample features. In this work, we focus on the second aspect, where we will compare established and novel metrics for S-OCT. These concepts include ...

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    7. Spectroscopic optical coherence tomography with graphics processing unit based analysis of three dimensional data sets

      Spectroscopic optical coherence tomography with graphics processing unit based analysis of three dimensional data sets

      Spectroscopic optical coherence tomography (OCT) is an extension of the standard backscattering intensity analysis of OCT. It enables depth resolved monitoring of molecular and structural differences of tissue. One drawback of most methods to calculate the spectroscopic data is the long processing time. Also systematic and stochastic errors make the interpretation of the results challenging. Our approach combines modern signal processing tools with powerful graphics processing unit (GPU) programming. The processing speed for the spectroscopic analysis is nearly 3 mega voxel per second. This allows us to analyze multiple B-Scans in a few seconds and to display the results as ...

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    8. Spectroscopic optical coherence tomography for substance identification

      Spectroscopic optical coherence tomography for substance identification

      We use Spectroscopic Optical Coherence Tomography (S-OCT) to identify substances by their spectral features in multi layer non-scattering samples. Depth resolved spectra are calculated by a windowed Fourier Transform in the spatial regime at discrete layer borders. By dividing subsequent spectra in an iterative manner transfer functions of the samples layers are calculated. Estimating these spectral transfer functions with high accuracy is still challenging, since the systems transfer function introduces an error, which can be orders of magnitude higher than the spectroscopic information of the sample. We retrieve the buried spectroscopic information of the sample with high accuracy by correcting ...

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    9. Comparison of optical coherence tomography, microcomputed tomography, and histology at a three-dimensionally imaged trabecular bone sample

      Comparison of optical coherence tomography, microcomputed tomography, and histology at a three-dimensionally imaged trabecular bone sample
      We investigate optical coherence tomography (OCT) as a method for imaging bone. The OCT images are compared directly to those of the standard methods of bone histology and microcomputed tomography (µCT) on a single, fixed human femoral trabecular bone sample. An advantage of OCT over bone histology is its noninvasive nature. OCT also images the lamellar structure of trabeculae at slightly higher contrast than normal bone histology. While µCT visualizes the trabecular framework of the whole sample, OCT can image additionally cells with a penetration depth limited approximately to 1 mm. The most significant advantage of OCT, however, is the ...
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    10. Frequency domain optical coherence tomography with subsequent depth resolved spectroscopic image analysis

      Frequency domain optical coherence tomography with subsequent depth resolved spectroscopic image analysis

      We present a method to obtain additional depth resolved spectroscopic information from standard frequency domain optical coherence tomography (FDOCT) images. This method utilizes Fourier transforms of signal peaks within the complex FDOCT depth profiles to extract depth resolved spectroscopic information. For verification of the depth resolved spectroscopic image analysis method, theoretical simulations as well as experimental studies are demonstrated. Both show accurate depth resolved spectroscopic reconstruction enabling a depth allocation of material specific transmission spectra due to absorption. This analysis tool improves significantly the image contrast and allows image mapping of material specific spectral characteristics.

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    11. Single-shot holography for depth resolved three dimensional imaging

      Single-shot holography for depth resolved three dimensional imaging
      We introduce a method for depth-resolved photorefractive holographic imaging with potentially extremely short acquisition time for a complete three dimensional (3D) image. By combining the advantages of full-field frequency-domain optical coherence tomography with those of photorefractive holography our concept is capable of obtaining 3D information with only one single shot. We describe the operation principle of our concept and give a first experimental proof of principle.
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    1-12 of 12
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  2. Topics in the News

    1. (12 articles) Martin R. Hofmann
    2. (12 articles) Nils C. Gerhardt
    3. (6 articles) Volker Jaedicke
    4. (4 articles) Christoph Kasseck
    5. (2 articles) Thorlabs
    6. (1 articles) K. U. Leuven
    7. (1 articles) Marita Kratz
    8. (1 articles) Antonia Torcasio
    9. (1 articles) Thilo Gambichler
    10. (1 articles) David B. Jones
    11. (1 articles) Sun Yat-Sen University
    12. (1 articles) National Institutes of Health
    13. (1 articles) University of Illinois at Urbana-Champaign
    14. (1 articles) Tianjin University
    15. (1 articles) Zhejiang University
    16. (1 articles) New York Eye and Ear Infirmary
    17. (1 articles) Eric J. Chaney
    18. (1 articles) Jun Zhang
    19. (1 articles) Robert Ritch
    20. (1 articles) Stephen A. Boppart
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    Single-shot holography for depth resolved three dimensional imaging Frequency domain optical coherence tomography with subsequent depth resolved spectroscopic image analysis Comparison of optical coherence tomography, microcomputed tomography, and histology at a three-dimensionally imaged trabecular bone sample Spectroscopic optical coherence tomography for substance identification Spectroscopic optical coherence tomography with graphics processing unit based analysis of three dimensional data sets Contrast enhancement methods in Optical Coherence Tomography using spectral features Comparison of different metrics for analysis and visualization in spectroscopic optical coherence tomography Multiwavelength phase unwrapping and aberration correction using depth filtered digital holography Spectroscopic optical coherence tomography for ex vivo brain tumor analysis Feature Of The Week 07/24/2017: Spectral Domain Optical Coherence Tomography for Non-Destructive Testing of Protection Coatings on Metal Substrates Optical coherence tomography angiography in glaucoma Handheld optical coherence tomography for clinical assessment of dental plaque and gingiva