Dr. Dietrich Schweitzer Profile

Dr. Dietrich Schweitzer

Lecturer

SPIE Involvement:

Author

Publications (29)

Proceedings Article | 4 March 2016 Paper

Effects of short term changes in the blood glucose level on the autofluorescence lifetime of the human retina in healthy volunteers

Matthias Klemm, Edgar Nagel, Dietrich Schweitzer, Stefan Schramm, Jens Haueisen

Proceedings Volume 9693, 96931R (2016) https://doi.org/10.1117/12.2208605

KEYWORDS: Spectral resolution, Glucose, Blood, Fluorescence lifetime imaging, Luminescence, Retina, Ophthalmoscopy, In vivo imaging, Scanning laser ophthalmoscopes, Sensors, Eye, Picosecond phenomena

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SPIE Journal Paper | 13 March 2015 Open Access

Fluorescence lifetime imaging ophthalmoscopy in type 2 diabetic patients who have no signs of diabetic retinopathy

Dietrich Schweitzer, Lydia Deutsch, Matthias Klemm, Susanne Jentsch, Martin Hammer, Sven Peters, Jens Haueisen, Ulrich Müller, Jens Dawczynski

JBO, Vol. 20, Issue 06, 061106, (March 2015) https://doi.org/10.1117/12.10.1117/1.JBO.20.6.061106

KEYWORDS: Luminescence, Picosecond phenomena, Fluorescence lifetime imaging, Ophthalmoscopy, Crystals, Control systems, Eye, Retina, Photons, Fluorescence spectroscopy

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Proceedings Article | 10 June 2011 Paper

Detection of early metabolic alterations in the ocular fundus of diabetic patients by time-resolved autofluorescence of endogenous fluorophores

D. Schweitzer, M. Klemm, S. Quick, L. Deutsch, S. Jentsch, M. Hammer, J. Dawczynski, C. Kloos, U. A. Mueller

Proceedings Volume 8087, 80871G (2011) https://doi.org/10.1117/12.889109

KEYWORDS: Picosecond phenomena, Fluorescence lifetime imaging, Luminescence, Retina, Eye, Oxygen, Mode conditioning cables, Laser scanners, Image registration, Macula

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Proceedings Article | 9 June 2011 Paper

Two-photon excited fluorescence microscopy application for ex vivo investigation of ocular fundus samples

Sven Peters, Martin Hammer, Dietrich Schweitzer

Proceedings Volume 8086, 808605 (2011) https://doi.org/10.1117/12.889807

KEYWORDS: Luminescence, Retina, Fluorescence lifetime imaging, Microscopy, Picosecond phenomena, Tissues, In vivo imaging, Thulium, Ophthalmology, Sapphire lasers

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SPIE Journal Paper | 1 November 2010 Open Access

Simple and objective method for routine detection of the macular pigment xanthophyll

Dietrich Schweitzer, Susanne Jentsch, Jens Dawczynski, Martin Hammer, Ute Wolf-Schnurrbusch, Sebastian Wolf

JBO, Vol. 15, Issue 06, 061714, (November 2010) https://doi.org/10.1117/12.10.1117/1.3526358

KEYWORDS: Absorbance, Stray light, Crystals, Eye, Cameras, Reflectivity, Objectives, Optical testing, Absorption, Retina

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Proceedings Article | 8 July 2009 Paper

Clinical results of fluorescence lifetime imaging in ophthalmology

D. Schweitzer, S. Quick, M. Klemm, M. Hammer, S. Jentsch, J. Dawczynski, W. Becker

Proceedings Volume 7368, 736802 (2009) https://doi.org/10.1117/12.831629

KEYWORDS: Picosecond phenomena, Luminescence, Ophthalmology, Laser scanners, Eye, Retina, Fluorescence spectroscopy, Mode conditioning cables, Crystals, Fluorescence lifetime imaging

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Proceedings Article | 8 July 2009 Paper

Method for simultaneous detection of functionality and tomography

D. Schweitzer, M. Klemm, M. Hammer, S. Jentsch, F. Schweitzer

Proceedings Volume 7368, 736804 (2009) https://doi.org/10.1117/12.831566

KEYWORDS: Luminescence, Eye, Fluorescence spectroscopy, Laser scanners, Crystals, Optical coherence tomography, Eye models, Picosecond phenomena, Tomography, Refractive index

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Proceedings Article | 25 February 2009 Paper

In vivo and in vitro investigations of retinal fluorophores in age-related macular degeneration by fluorescence lifetime imaging

M. Hammer, S. Quick, M. Klemm, S. Schenke, N. Mata, A. Eitner, D. Schweitzer

Proceedings Volume 7183, 71832S (2009) https://doi.org/10.1117/12.807943

KEYWORDS: Luminescence, Fluorescence lifetime imaging, Retina, Picosecond phenomena, In vivo imaging, Tissues, Eye, In vitro testing, Diagnostics, Proteins

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Proceedings Article | 24 February 2009 Paper

A new imaging technique for retinal vessel oximetry: principles and first clinical results in patients with retinal arterial occlusion and diabetic retinopathy

M. Hammer, T. Riemer, W. Vilser, S. Gehlert, D. Schweitzer

Proceedings Volume 7163, 71630P (2009) https://doi.org/10.1117/12.807817

KEYWORDS: Oxygen, Cameras, Oximetry, Calibration, Optical filters, Blood circulation, Blood, Retina, Image segmentation, Tissues

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SPIE Journal Paper | 1 September 2008 Open Access

Retinal vessel oximetry-calibration, compensation for vessel diameter and fundus pigmentation, and reproducibility

Martin Hammer, Walthard Vilser, Thomas Riemer, Dietrich Schweitzer

JBO, Vol. 13, Issue 05, 054015, (September 2008) https://doi.org/10.1117/12.10.1117/1.2976032

KEYWORDS: Oxygen, Cameras, Oximetry, Image segmentation, Calibration, Optical filters, Oximeters, Spectroscopy, Absorbance, Diagnostics

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Proceedings Article | 15 October 2007 Paper

Interpretation of measurements of dynamic fluorescence of the eye

Dietrich Schweitzer, Martin Hammer, Susanne Jentsch, Stefan Schenke

Proceedings Volume 6771, 677108 (2007) https://doi.org/10.1117/12.735815

KEYWORDS: Luminescence, Retina, Tissues, Cornea, Eye, Sclera, Vitreous, Macula, Fluorescence spectroscopy, Oxygen

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Proceedings Article | 11 July 2007 Paper

Spectral and time-resolved studies on ocular structures

D. Schweitzer, S. Jentsch, S. Schenke, M. Hammer, C. Biskup, E. Gaillard

Proceedings Volume 6628, 662807 (2007) https://doi.org/10.1117/12.726701

KEYWORDS: Luminescence, Retina, Sclera, Cornea, Vitreous, Picosecond phenomena, Eye, Fluorescence spectroscopy, Tissues, Collagen

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Proceedings Article | 25 October 2006 Paper

Differentiation of ocular fundus fluorophores by fluorescence lifetime imaging using multiple excitation and emission wavelengths

M. Hammer, D. Schweitzer, S. Schenke, W. Becker, A. Bergmann

Proceedings Volume 6372, 637202 (2006) https://doi.org/10.1117/12.684989

KEYWORDS: Luminescence, Fluorescence lifetime imaging, Collagen, Picosecond phenomena, Diagnostics, Eye, Proteins, Auto-fluorescence imaging, Retina, Data modeling

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Proceedings Article | 7 March 2006 Paper

In vivo autofluorescence lifetime imaging at the fundus of the human eye

Dietrich Schweitzer, Martin Hammer, Frank Schweitzer, Stefan Schenke, Eckhard Birckner, Wolfgang Becker, Axel Bergmann

Proceedings Volume 6138, 613808 (2006) https://doi.org/10.1117/12.644692

KEYWORDS: Luminescence, Picosecond phenomena, Eye, Fluorescence lifetime imaging, Mode conditioning cables, In vivo imaging, Laser scanners, Single photon, Oxygen, Fluorescence spectroscopy

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Proceedings Article | 8 October 2005 Paper

Time- and wavelength-resolved autofluorescence detection by multi-dimensional TCSPC

Wolfgang Becker, Axel Bergmann, Christoph Biskup, Dietrich Schweitzer, Martin Hammer

Proceedings Volume 5862, 58620S (2005) https://doi.org/10.1117/12.633033

KEYWORDS: Luminescence, Eye, Fluorescence lifetime imaging, Tissues, Signal detection, Sensors, Picosecond phenomena, Ophthalmic imaging, Photodetectors, Skin

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Proceedings Article | 8 October 2005 Paper

Comparison of time-resolved autofluorescence in the eye-ground of healthy subjects and patients suffering from age-related maculer degeneration

Dietrich Schweitzer, Frank Schweitzer, Martin Hammer, Stefan Schenke, Sandra Richter

Proceedings Volume 5862, 58620R (2005) https://doi.org/10.1117/12.633032

KEYWORDS: Luminescence, Picosecond phenomena, Fluorescence spectroscopy, Macula, Absorption, In vivo imaging, Connective tissue, Reflectivity, Crystals, Laser scanners

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SPIE Journal Paper | 1 November 2004 Open Access

In vivo measurement of time-resolved autofluorescence at the human fundus

Dietrich Schweitzer, Martin Hammer, Frank Schweitzer, Roswitha Anders, Torsten Doebbecke, Stefan Schenke, E. Gaillard, Elizabeth Gaillard

JBO, Vol. 9, Issue 06, (November 2004) https://doi.org/10.1117/12.10.1117/1.1806833

KEYWORDS: Luminescence, Picosecond phenomena, Oxygen, Macula, Optical discs, Fluorescence spectroscopy, Eye, Photons, Spatial resolution, Signal detection

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Proceedings Article | 8 October 2003 Paper

Evaluation of time-resolved autofluorescence images of the ocular fundus

Dietrich Schweitzer, Martin Hammer, Frank Schweitzer, Stefan Schenke, Elizabeth Gaillard

Proceedings Volume 5141, (2003) https://doi.org/10.1117/12.499641

KEYWORDS: Luminescence, Oxygen, Eye, Picosecond phenomena, Mode conditioning cables, Laser scanners, Macula, Spatial resolution, In vivo imaging, Photons

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Proceedings Article | 31 October 2001 Paper

Autofluorescence lifetime measurements in images of the human ocular fundus

Dietrich Schweitzer, Achim Kolb, Martin Hammer

Proceedings Volume 4432, (2001) https://doi.org/10.1117/12.447153

KEYWORDS: Luminescence, Photons, Oxygen, Laser scanners, Tissue optics, Eye, Fluorescence spectroscopy, Retina, Single photon, Absorption

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Proceedings Article | 18 December 2000 Paper

Tau mapping of the autofluorescence of the human ocular fundus

Dietrich Schweitzer, Achim Kolb, Martin Hammer, Eike Thamm

Proceedings Volume 4164, (2000) https://doi.org/10.1117/12.410636

KEYWORDS: Luminescence, Photons, Eye, Signal detection, Time metrology, Laser scanners, In vivo imaging, Single photon, Picosecond phenomena, Light scattering

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Proceedings Article | 22 December 1997 Paper

Monte-Carlo simulation of retinal vessel profiles for the interpretation of in-vivo oxymetric measurements by imaging fundus reflectometry

Martin Hammer, S. Leistritz, Lutz Leistritz, Dietrich Schweitzer, Eike Thamm, Karl-Heinz Donnerhacke

Proceedings Volume 3192, (1997) https://doi.org/10.1117/12.297857

KEYWORDS: Blood, Monte Carlo methods, In vivo imaging, Reflectometry, Oxygen, Reflectivity, Backscatter, Software development, Absorption, Retina

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Background: The oxygen utilization, and therefore the metabolic state, of a distinctive area of the retina may be calculated from the diameter of the supplying artery and vein, the haemoglobin oxygenation, and the velocity of the blood. The first two parameters can be determined by imaging spectrometry at the patients ocular fundus. This technique enables the simultaneous measurement of reflectance spectra of neighboring locations at the fundus, e.g. across retinal vessels. However, the reflected light emerging from a vessel is determined by different mechanisms of reflection and backscattering. The following most significant light fractions, contributing to the measuring signal, are considered: Light which is backscattered from deeper fundus layers and transmitted once or twice through the vessel, light which is backscattered from the blood column inside the vessel, and light which is specular reflected at the vessel wall. Goals are the investigation of the contribution of the single fractions to the vessel profile and its approximation by an analytical function which can be used to compensate specular reflection at in vivo measured profiles. Method: To evaluate the contribution of the different pathways we set up a Monte Carlo model of radiative transport inside the ocular fundus as a layered structure containing a vessel with circular cross section. The developed software is able to distinguish photons contributing to the simulated vessel profile which penetrated the blood column once, twice, or never. Experimentally determined absorption and scattering parameters of the fundus tissues were used in the simulation. Results: Considering retinal vessels with diameters of 25 micrometers to 200 micrometers we found the reflection from a thin vessel to be determined by the single and double transmission of light at 559 nm. The backscattering from the blood column determines the reflectance in the case of a thick vessel. However, both components are in the same order of magnitude. Discussion: The spectra measured even at the center of retinal branch vessels are composed from light which is backscattered from the blood column inside the vessel and from transmitted light fractions which were reflected behind the vessel. Since the latter is influenced also by the absorption of melanin and haemoglobin in the choroid, care must be taken in the calculation of the oxygen saturation of blood in retinal vessels from this spectra. The reconstruction of an in vivo measured vessel profile which is distorted by specular reflexes is possible by the use of a polynomial of sixth degree.

SPIE Journal Paper | 1 October 1997 Open Access

Imaging spectroscopy of the human ocular fundus in vivo

Martin Hammer, Dietrich Schweitzer, Lutz Leistritz, Mateusz Scibor, Karl-Heinz Donnerhacke, Juergen Strobel

JBO, Vol. 2, Issue 04, (October 1997) https://doi.org/10.1117/12.10.1117/12.285093

KEYWORDS: Reflectivity, In vivo imaging, Eye, Confocal microscopy, Image resolution, Cameras, Absorbance, Charge-coupled devices, Spectroscopy, Imaging spectroscopy

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Proceedings Article | 5 December 1996 Paper

Simultaneous measurement of oxygen saturation and vessel diameter by imaging spectrometry

Dietrich Schweitzer, Lutz Leistritz, Martin Hammer, Ulrich Bartsch, Mateusz Scibor, J. Kraft, C. Muench, W. Vilser, E. Bareshova, P. Putsche

Proceedings Volume 2930, (1996) https://doi.org/10.1117/12.260862

KEYWORDS: Oxygen, Blood, Scattering, Spectroscopy, Reflectivity, Light scattering, Absorption, Imaging spectrometry, Eye, Veins

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Proceedings Article | 5 December 1996 Paper

Laser scanner ophthalmoscope with free selectable wavelength

Dietrich Schweitzer, B. Kalve, Lutz Leistritz, Mateusz Scibor, Martin Hammer

Proceedings Volume 2930, (1996) https://doi.org/10.1117/12.260863

KEYWORDS: Laser scanners, Eye, Absorbance, Sensors, Signal to noise ratio, Laser systems engineering, Reflectivity, Bragg cells, Multispectral imaging, Oxygen

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Proceedings Article | 10 January 1996 Paper

Local resolved spectroscopy at the human ocular fundus in vivo: technique and clinical examples

Martin Hammer, Dietrich Schweitzer, Mateusz Scibor

Proceedings Volume 2632, (1996) https://doi.org/10.1117/12.229577

KEYWORDS: Reflectivity, Absorption, Reflectometry, Spectrographs, Cameras, Macula, Eye models, CCD cameras, Spectroscopy, In vivo imaging

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Proceedings Article | 22 May 1995 Paper

Calibration-free measurement of the oxygen saturation in human retinal vessels

Dietrich Schweitzer, Lutz Leistritz, Martin Hammer, Mateusz Scibor, Ulrich Bartsch, Juergen Strobel

Proceedings Volume 2393, (1995) https://doi.org/10.1117/12.209850

KEYWORDS: Oxygen, Blood, Scattering, Reflectivity, Brain, Spectroscopy, Signal attenuation, In vitro testing, Calibration, In vivo imaging

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The detection of alterations in the microcirculation requires both the measurement of the blood-flow and the measurement of the oxygen saturation in whole blood. The basis for the non-invasive estimation of the oxygen saturation is the difference between extinction-spectra of hemoglobin and of oxyhemoglobin. Further in whole blood the scattering at the erythrocytes has to be taken into account. In principle spectral measurements at three neighboring wavelengths are sufficient for the calculation of the oxygen saturation, the concentration- thickness-geometry product and the scattering intensity. Caused by the maximal permissible exposure, the signal/noise ratio is very low in fundus reflectometry. But if the wavelength- range from 520 nm to 620 nm is evaluated, the requirement at the signal/noise ratio is reduced. This reduction corresponds to the square root of the number of discrete wavelengths at which the ocular fundus reflectance is measured. So the oxygen saturation can be calculated with an error lower than +/- 4%. For this purpose the extinction spectrum of whole blood is approximated by a model, including besides the above mentioned unknowns the spectral dependency of the scattering. The experimental arrangement for the measurement of the oxygen saturation is an imaging ophthalmo-spectrometer which allows reflectance measurements with a good spectral (< 3 nm) and local (> 3 micrometers ) resolution simultaneously at a vessel and in its neighborhood. The extinction of blood is calculated as the logarithm of the ratio of the reflectance of the neighborhood and of the vessel. In this calculation the influences of the ocular media, of the background and of eye movements are eliminated. The sensitivity of the detector system has to be very high in order to detect the light which is reflected at a dark background and travels through the blood. The new method was tested by a comparison the oxygen saturation of the blood in an arteriole and a venule in the brain of a piglet measured by reflectometry with the oxygen saturation of the left ventricular and the venous blood measured by a laboratory hemoximeter. First results of the measurement of the oxygen saturation in human retinal vessels are demonstrated.

Proceedings Article | 18 January 1995 Paper

Absorption and scattering in the single layers of the ocular fundus

Martin Hammer, Andre Roggan, Dietrich Schweitzer

Proceedings Volume 2323, (1995) https://doi.org/10.1117/12.199208

KEYWORDS: Scattering, Absorption, Tissues, Retina, Monte Carlo methods, Light scattering, Reflectivity, Blood, Sclera, In vivo imaging

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Proceedings Article | 21 September 1994 Paper

Automated detection and quantification of exudates in retinal images

Lutz Leistritz, Dietrich Schweitzer

Proceedings Volume 2298, (1994) https://doi.org/10.1117/12.186598

KEYWORDS: Eye, Nerve, Scanning laser ophthalmoscopes, Reflectivity, Head, Algorithm development, Vignetting, Scanning laser ophthalmoscopy, Detection and tracking algorithms, Optic nerve

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