Dr. Alexander Ehlers Profile

Dr. Alexander Ehlers

at Fraunhofer-Institut für Biomedizinische Technik

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Author

Publications (18)

Proceedings Article | 13 February 2009 Paper

New developments in two-photon analysis of human skin in vivo

I. Riemann, M. Schwarz, F. Stracke, A. Ehlers, E. Dimitrow, M. Kaatz, K. König, R. Le Harzic

Proceedings Volume 7203, 720306 (2009) https://doi.org/10.1117/12.808770

KEYWORDS: Skin, Tissues, Fluorescence lifetime imaging, In vivo imaging, Collagen, Melanoma, Second-harmonic generation, Atrial fibrillation, Biopsy, Multiphoton tomography

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Proceedings Article | 21 February 2008 Paper

Two-photon imaging using a flexible endoscope

Iris Riemann, Selma Schenkl, Ronan Le Harzic, Daniel Sauer, Alexander Ehlers, Bernhard Messerschmidt, Rainer Bückle, Karsten König

Proceedings Volume 6851, 68510B (2008) https://doi.org/10.1117/12.762970

KEYWORDS: Luminescence, Endoscopes, Tissues, Photonic crystal fibers, Scanners, Fiber lasers, Two photon imaging, Microscopes, GRIN lenses, Image resolution

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Proceedings Article | 8 February 2008 Paper

Non-invasive analysis/diagnosis of human normal and melanoma skin tissues with two-photon FLIM in vivo

Iris Riemann, Alexander Ehlers, Ronan Le Harzic, Enrico Dimitrow, Martin Kaatz, P. Elsner, Rainer Bückle, Karsten König

Proceedings Volume 6842, 684205 (2008) https://doi.org/10.1117/12.762937

KEYWORDS: Tissues, Melanoma, Skin, Fluorescence lifetime imaging, In vivo imaging, Biopsy, Proteins, Biological research, Optical tomography, Luminescence

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Proceedings Article | 23 July 2007 Paper

In vivo multiphoton tomography: a non invasive powerful tool for biochemical investigation of human skin

Ronan Le Harzic, Anne Colonna, Rainer Bückle, Alexander Ehlers, Christophe Hadjur, Frederic Leroy, Frederic Flament, Roland Bazin, Bertrand Piot, Iris Riemann, Karsten König

Proceedings Volume 6630, 66300V (2007) https://doi.org/10.1117/12.727044

KEYWORDS: Atrial fibrillation, Second-harmonic generation, Collagen, Skin, In vivo imaging, Harmonic generation, Multiphoton tomography, Single photon, Photomultipliers, Biomedical optics

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Proceedings Article | 18 July 2007 Paper

Rigid and high NA multiphoton fluorescence GRIN-endoscopes

Selma Schenkl, Alexander Ehlers, Ronan Le Harzic, Martin Stark, Iris Riemann, Bernhard Messerschmidt, Martin Kaatz, Karsten König

Proceedings Volume 6631, 66310Q (2007) https://doi.org/10.1117/12.728503

KEYWORDS: Skin, Imaging systems, Luminescence, GRIN lenses, Image resolution, Collagen, In vivo imaging, Endoscopes, Signal detection, Microscopes

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Proceedings Article | 11 July 2007 Paper

Multiphoton imaging and fluorescence lifetime studies on unstained cells and tissue at cryogenic conditions

Martin Stark, Daniel Dörr, Alexander Ehlers, Daniel Sauer, Rainer Bückle, Sven Martin, Friederike Ehrhart, Jennifer Baunach, Alisa Katsen-Globa, Heiko Zimmermann, Karsten König

Proceedings Volume 6628, 662809 (2007) https://doi.org/10.1117/12.728317

KEYWORDS: Luminescence, Tissues, Scattering, Photons, Liquids, Multiphoton microscopy, Absorption, Cryogenics, Light scattering, Laser scattering

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Proceedings Article | 23 March 2007 Paper

Multiphoton tomography of skin tumors after ALA application

Iris Riemann, Alexander Ehlers, Dorothee Dill-Müller, Sven Martin, Karsten König

Proceedings Volume 6424, 642405 (2007) https://doi.org/10.1117/12.702411

KEYWORDS: Skin, Photodynamic therapy, Luminescence, Multiphoton tomography, Biopsy, Tissues, Tumors, Skin cancer, Near infrared, Therapeutics

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Proceedings Article | 15 February 2007 Paper

Applications of rigid and flexible GRIN-endoscopes

Selma Schenkl, Alexander Ehlers, Iris Riemann, Bernhard Messerschmidt, Rainer Bückle, Karsten König

Proceedings Volume 6433, 64330N (2007) https://doi.org/10.1117/12.702413

KEYWORDS: Endoscopes, Imaging systems, GRIN lenses, Objectives, Microscopes, Collagen, Luminescence, Skin, Tissues, Signal detection

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Proceedings Article | 12 February 2007 Paper

Novel concept of GRIN optical systems for high resolution microendoscopy: Part 1. Physical aspects

Bernhard Messerschmidt, Anke Kraeplin, Selma Schenkl, Iris Riemann, Martin Stark, Alexander Ehlers, Andrei Tchernook, Ronan Le Harzic, Karsten Koenig

Proceedings Volume 6432, 643202 (2007) https://doi.org/10.1117/12.698831

KEYWORDS: GRIN lenses, Objectives, Image quality, Tissue optics, Luminescence, Glasses, Monochromatic aberrations, Imaging systems, Tissues, Image resolution

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Proceedings Article | 10 February 2007 Paper

Clinical in vivo two-photon microendoscopy for intradermal high-resolution imaging with GRIN optics

Karsten König, Alexander Ehlers, Iris Riemann, Selma Schenkl, Bernhard Messerschmidt, Rainer Bückle, Ronan Le Harzic, Peter Elsner, Martin Kaatz

Proceedings Volume 6442, 644215 (2007) https://doi.org/10.1117/12.702380

KEYWORDS: GRIN lenses, Collagen, In vivo imaging, Skin, Imaging systems, Femtosecond phenomena, Endoscopes, Multiphoton tomography, Gradient-index optics, Second-harmonic generation

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Proceedings Article | 10 February 2007 Paper

In-vivo multiphoton-endoscopy of endogenous skin fluorophores

Alexander Ehlers, Selma Schenkl, Iris Riemann, Bernhard Messerschmidt, Martin Kaatz, Rainer Bückle, Karsten König

Proceedings Volume 6442, 64421Y (2007) https://doi.org/10.1117/12.702394

KEYWORDS: Endoscopes, Skin, GRIN lenses, Second-harmonic generation, In vivo imaging, Collagen, Luminescence, Multiphoton tomography, Gradient-index optics, Tissue optics

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Proceedings Article | 10 February 2007 Paper

In vivo multiphoton tomography of skin during wound healing and scar formation

Iris Riemann, Alexander Ehlers, Ronan LeHarzic, Sven Martin, Annette Reif, Karsten König

Proceedings Volume 6442, 644226 (2007) https://doi.org/10.1117/12.702407

KEYWORDS: Skin, Tissues, In vivo imaging, Wound healing, Multiphoton tomography, Collagen, Near infrared, Optical fibers, Second-harmonic generation, Multiphoton microscopy

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Proceedings Article | 2 March 2006 Paper

High-resolution multiphoton optical tomography of tissues: an in vitro and in vivo study

Iris Riemann, Katja Schenke-Layland, Alexander Ehlers, Enrico Dimitrow, Martin Kaatz, Peter Elsner, Sven Martin, Karsten König

Proceedings Volume 6142, 61420N (2006) https://doi.org/10.1117/12.651358

KEYWORDS: Tissues, In vivo imaging, Collagen, Heart, Skin, Near infrared, Optical fibers, Second-harmonic generation, Optical tomography, In vitro testing

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Proceedings Article | 23 February 2006 Paper

Fluorescence lifetime imaging of human skin and hair

A. Ehlers, I. Riemann, T. Anhut, M. Kaatz, P. Elsner, K. König

Proceedings Volume 6089, 60890N (2006) https://doi.org/10.1117/12.645714

KEYWORDS: Skin, Fluorescence lifetime imaging, Luminescence, In vivo imaging, Collagen, Second-harmonic generation, Sensors, Tissues, Image resolution, Chemical analysis

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Proceedings Article | 23 February 2006 Paper

In vivo multiphoton tomography of skin cancer

Karsten König, Iris Riemann, Alexander Ehlers, Rainer Buckle, Enrico Dimitrow, Martin Kaatz, Joachim Fluhr, Peter Elsner

Proceedings Volume 6089, 60890R (2006) https://doi.org/10.1117/12.646000

KEYWORDS: Tissues, Luminescence, Skin, Melanoma, In vivo imaging, Multiphoton tomography, Near infrared, Tissue optics, Second-harmonic generation, Fluorescence lifetime imaging

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Proceedings Article | 28 October 2005 Paper

In-vivo non-invasive multiphoton tomography of human skin

Karsten König, Iris Riemann, Alexander Ehlers, Ronan Le Harzic

Proceedings Volume 5990, 59900W (2005) https://doi.org/10.1117/12.629658

KEYWORDS: Skin, Tissues, Luminescence, Tissue optics, In vivo imaging, Near infrared, Femtosecond phenomena, Second-harmonic generation, Ultraviolet radiation, Imaging systems

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High resolution non-invasive 3D imaging devices are required to detect pathogenic microorganisms such as Anthrax spores, bacteria, viruses, fungi and chemical agents entering biological tissues such as the epidermis. Due to the low light penetration depth and the biodamage potential, ultraviolet light sources can not be employed to realize intratissue imaging of bio- and chemohazards. We report on the novel near infrared laser technology multiphoton tomography and the high resolution 4D imaging tool DermaInspect for non-invasive detection of intratissue agents and their influence on cellular metabolism based on multiphoton autofluorescence imaging (MAI) and second harmonic generation (SHG). Femtosecond laser pulses in the spectral range of 750 nm to 850 nm have been used to image in vivo human skin with subcellular spatial and picosecond temporal resolution. The non-linear induced autofluorescence of both, skin tissues and microorganisms, originates mainly from naturally endogenous fluorophores/protein structures like NAD(P)H, flavins, keratin, collagen, elastin, porphyrins and melanin. Bacteria emit in the blue/green spectral range due to NAD(P)H and flavoproteins and, in certain cases, in the red spectral range due to the biosynthesis of Zn-porphyrins, coproporphyrin and protoporphyrin. Collagen and exogenous non-centrosymmetric molecules can be detected by SHG signals. The system DermaInspect consists of a wavelength-tunable compact 80/90 MHz Ti:sapphire laser, a scan module with galvo scan mirrors, piezo-driven objective, fast photon detector and time-resolved single photon counting unit. It can be used to perform optical sectioning and 3D autofluorescence lifetime imaging (τ-mapping) with 1 μm spatial resolution and 270 ps temporal resolution. The parameter fluorescence lifetime depends on the type of fluorophore and its microenvironment and can be used to distinguish bio- and chemohazards from cellular background and to gain information for pathogen identification. The novel in vivo non-invasive imaging system offers the possibility to detect and to localize CB agents in tissues and to gain information on their impact on respiratory chain activity, cell division and metabolism. The system DermaInspect can also be used to detect food and water contamination.

Proceedings Article | 25 April 2005 Paper

In vivo multiphoton tomography of skin as a tool to study the effects of topically applied probes and UV exposure

Iris Riemann, Alexander Ehlers, Annette Reif, Jens Kobow, Karsten Konig

Proceedings Volume 5686, (2005) https://doi.org/10.1117/12.590817

KEYWORDS: Skin, In vivo imaging, Tissues, Ultraviolet radiation, Near infrared, Confocal microscopy, Femtosecond phenomena, Tissue optics, Image resolution, Optical tomography

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Proceedings Article | 30 March 2005 Paper

Multiphoton tomography of epidermis and dermis

Alexander Ehlers, Iris Riemann, Tiemo Anhut, Jens Kobow, Karsten Konig

Proceedings Volume 5700, (2005) https://doi.org/10.1117/12.590411

KEYWORDS: Skin, Imaging systems, Luminescence, Objectives, In vivo imaging, Second-harmonic generation, Tissues, GRIN lenses, Collagen, Pulsed laser operation

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Showing 5 of 18 publications

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