1. Articles from Alexander Krüger

    1-6 of 6
    1. Adaptive optics assisted and optical coherence tomography guided fs-laser system for ophthalmic surgery in the posterior eye

      Adaptive optics assisted and optical coherence tomography guided fs-laser system for ophthalmic surgery in the posterior eye

      While fs-lasers are clinically established for surgery in the anterior eye, their use in the posterior eye is impeded by aberrations and focus position errors. We implemented a laboratory system to investigate whether fs-laser surgery in the posterior eye is made more feasible by aberration correction and tomographic image guidance. Aberration correction is obtained by adaptive optics (AO) and the image guidance is accomplished by optical coherence tomography (OCT). System characteristic measurements and cutting experiments were performed inside an eye model. By aberration correction, wavefront errors were reduced from 270 nm root-mean-square (rms) to 64 nm rms, ignoring Zernike terms ...

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    2. Towards femtosecond laser surgery guidance in the posterior eye: utilization of optical coherence tomography and adaptive optics for focus positioning and shaping

      Towards femtosecond laser surgery guidance in the posterior eye: utilization of optical coherence tomography and adaptive optics for focus positioning and shaping

      Although fs-laser surgery is clinically established in the field of corneal flap cutting for laser in situ keratomileusis, surgery with fs-laser in the posterior part of the eye is impaired by focus degradation due to aberrations. Precise targeting and keeping of safety distance to the retina also relies on an intraoperative depth resolved imaging. We demonstrate a concept for image guided fs-laser surgery in the vitreous body combining adaptive optics (AO) for focus reshaping and optical coherence tomography (OCT) for focus position guidance. The setup of the laboratory system consist of an 800 nm fs-laser which is focused into a ...

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    3. In situ optical coherence tomography of percutaneous implant-tissue interfaces in a murine model

      In situ optical coherence tomography of percutaneous implant-tissue interfaces in a murine model

      Novel surface coatings of percutaneous implants need to be tested in biocompatibility studies. The use of animal models for testing usually involves numerous lethal biopsies for the analysis of the implant-tissue interface. In this study, optical coherence tomography (OCT) was used to monitor the reaction of the skin to a percutaneous implant in an animal model of hairless but immunocompetent mice. In vivo optical biopsies with OCT were taken at days 7 and 21 after implantation and post mortem on the day of noticeable inflammation. A Fourier-domain OCT was programmed for spoke pattern scanning schemes centered at the implant midpoint ...

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    4. Feature Of The Week 12/4/11: Researchers in Hannover Germany Utilize OCT to Measure Skin Swelling Along Percutaneous Implants

      Feature Of The Week 12/4/11: Researchers in Hannover Germany Utilize OCT to Measure Skin Swelling Along Percutaneous Implants
      Researchers from the Leibniz University of Hannover (LUH), Laser Zentrum Hannover (LZH), and the Hannover Medical School (MHH) used OCT to measure skin swelling along percutaneous implants. An undistortion technique is proposed to compensate for the refractive distortions [1].Optical Coherence Tomography is a non invasive imaging modality recently used for taking high resolution optical biopsies of layered tissue structures such as the epidermis and the retina.As the OCT system captures optical distances rather than geometrical distances, the optical properties of the tissue introduce distortions into the OCT images. Therefore, model based image undistortion is an important step for ...
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    5. Model Based 3D Segmentation and OCT Image Undistortion of Percutaneous Implants

      Model Based 3D Segmentation and OCT Image Undistortion of Percutaneous Implants
      Optical Coherence Tomography (OCT) is a noninvasive im-aging technique which is used here for in vivo biocompatibility studies of percutaneous implants. A prerequisite for a morphometric analysis of the OCT images is the correction of optical distortions caused by the index of refraction in the tissue. We propose a fully automatic approach for 3D segmentation of percutaneous implants using Markov random fields. Refraction correction is done by using the subcutaneous implant base as a prior for model based estimation of the refractive index using a generalized Hough transform. Experiments show the competitiveness of our algorithm towards manual segmentations done by ...
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    6. Effects of axial, transverse, and oblique sample motion in FD OCT in systems with global or rolling shutter line detector

      This study deals with effects on the interference signal caused by axial, transverse, and oblique motion in spectrometer-based Fourier-domain optical coherence tomography (FD OCT). Two different systems are compared--one with a global shutter line detector and the other with a rolling shutter. We ... [J. Opt. Soc. Am. A 25, 2791-2802 (2008)]
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    1-6 of 6
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  2. Topics in the News

    1. (6 articles) Alexander Krüger
    2. (5 articles) Laser Zentrum Hannover
    3. (3 articles) University of Hannover
    4. (3 articles) Oliver Müller
    5. (3 articles) Bodo Rosenhahn
    6. (3 articles) Sabine Donner
    7. (3 articles) Ivonne Bartsch
    8. (2 articles) Hannover Medical School
    9. (2 articles) Philips Healthcare
    10. (2 articles) Tobias Klinder
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    Model Based 3D Segmentation and OCT Image Undistortion of Percutaneous Implants Feature Of The Week 12/4/11: Researchers in Hannover Germany Utilize OCT to Measure Skin Swelling Along Percutaneous Implants In situ optical coherence tomography of percutaneous implant-tissue interfaces in a murine model Towards femtosecond laser surgery guidance in the posterior eye: utilization of optical coherence tomography and adaptive optics for focus positioning and shaping Adaptive optics assisted and optical coherence tomography guided fs-laser system for ophthalmic surgery in the posterior eye Retinal Vascular Features in Ocular Blunt Trauma by Optical Coherence Tomography Angiography Non-invasive imaging of a choroidal macrovessel Correlation between optical coherence tomography, multifocal electroretinogram findings and visual acuity in diabetic macular edema Digital Wavefront Sensing Ciliary body length revisited by anterior segment optical coherence tomography: implications for safe access to the pars plana for intravitreal injections Evaluation of retinal vascular structure after epiretinal membrane surgery by optical coherence tomography angiography Bivalirudin vs. Heparin on Radial Artery Thrombosis during Transradial Coronary Intervention: An Optical Coherence Tomography Study