Dr. Clemens Alt Profile

Dr. Clemens Alt

Instructor at Wellman Ctr for Photomedicine

SPIE Involvement:

Author

Publications (10)

Proceedings Article | 20 February 2018 Presentation + Paper

In vivo flow cytometry for blood cell analysis using differential epi-detection of forward scattered light

Hari Paudel, Yookyung Jung, Anthony Raphael, Clemens Alt, Juwell Wu, Judith Runnels, Charles Lin

Proceedings Volume 10497, 104970G (2018) https://doi.org/10.1117/12.2288514

KEYWORDS: Flow cytometry, Phase contrast, In vivo imaging, Light scattering, Imaging systems

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Proceedings Article | 9 March 2012 Paper

In vivo quantification of microglia dynamics with a scanning laser ophthalmoscope in a mouse model of focal laser injury

Clemens Alt, Charles Lin

Proceedings Volume 8209, 820907 (2012) https://doi.org/10.1117/12.909141

KEYWORDS: Injuries, Blood vessels, Scanning laser ophthalmoscopy, In vivo imaging, Reflectivity, Continuous wave operation, Bragg cells, Image processing, Angiography, Retina

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Proceedings Article | 9 February 2012 Paper

In vivo cell tracking and quantification method in adult zebrafish

Li Zhang, Clemens Alt, Pulin Li, Richard White, Leonard Zon, Xunbin Wei, Charles Lin

Proceedings Volume 8225, 82250P (2012) https://doi.org/10.1117/12.909632

KEYWORDS: In vivo imaging, Confocal microscopy, Green fluorescent protein, Imaging systems, Stem cells, Flow cytometry, Blood vessels, Beam splitters, Skin, Blood

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Proceedings Article | 3 March 2010 Paper

An adaptive-optics scanning laser ophthalmoscope for imaging murine retinal microstructure

Clemens Alt, David Biss, Nadja Tajouri, Tatjana Jakobs, Charles Lin

Proceedings Volume 7550, 755019 (2010) https://doi.org/10.1117/12.840583

KEYWORDS: Adaptive optics, Axons, Luminescence, Eye, Scanning laser ophthalmoscopy, Retinal scanning, Blood vessels, Mirrors, Retina, Scanning laser ophthalmoscopes

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SPIE Journal Paper | 1 November 2007 Open Access

Optical detection of intracellular cavitation during selective laser targeting of the retinal pigment epithelium: dependence of cell death mechanism on pulse duration

Ho Lee, Clemens Alt, Costas Pitsillides, Charles Lin

JBO, Vol. 12, Issue 06, 064034, (November 2007) https://doi.org/10.1117/12.10.1117/1.2804078

KEYWORDS: Cavitation, Cell death, Backscatter, Particles, Pulsed laser operation, Sensors, Scattering, Luminescence, Biomedical optics, Laser scattering

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Proceedings Article | 19 February 2007 Paper

In vivo imaging flow cytometer

Clemens Alt, Ho Lee, Costas Pitsillides, Mehron Puoris'haag, Charles Lin

Proceedings Volume 6441, 64410I (2007) https://doi.org/10.1117/12.702180

KEYWORDS: In vivo imaging, Luminescence, Velocity measurements, Confocal microscopy, Microscopes, Blood, Ear, Beam splitters, Imaging systems, Blood vessels

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SPIE Journal Paper | 1 November 2005 Open Access

Selective targeting of the retinal pigment epithelium using an acousto-optic laser scanner

Clemens Alt, Carsten Framme, Susanne Schnell, Ho Lee, Ralf Brinkmann, Charles Lin

JBO, Vol. 10, Issue 06, 064014, (November 2005) https://doi.org/10.1117/12.10.1117/1.2136314

KEYWORDS: In vitro testing, Angiography, Luminescence, In vivo imaging, Eye, Continuous wave operation, Retina, Scanners, Laser scanners, Frequency modulation

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Proceedings Article | 14 July 2003 Paper

Monitoring intracellular cavitation during selective targeting of the retinal pigment epithelium

Clemens Alt, Costas Pitsillides, Jan Roegener, Charles Lin

Proceedings Volume 4951, (2003) https://doi.org/10.1117/12.477956

KEYWORDS: Cavitation, Signal detection, Cell death, Retina, Lamps, Laser damage threshold, In vitro testing, In vivo imaging, Laser coagulation, Pulsed laser operation

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Selective targeting of the Retinal Pigment Epithelium (RPE), by either applying trains of microsecond laser pulses or, in our approach, by repetitively scanning a tightly focused spot across the retina, achieves destruction of RPE cells while avoiding damage to the overlying photoreceptors. Both techniques have been demonstrated as attractive methods for the treatment of retinal diseases that are caused by a dysfunction of the RPE. Because the lesions are ophthalmoscopically invisible, an online control system that monitors cell death during irradiation is essential to ensure efficient and selective treatment in a clinical application. Bubble formation inside the RPE cells has been shown to be the cell damage mechanism for nano- and picosecond pulses. We built an optical system to investigate whether the same mechanism extends into the microsecond regime. The system detects changes in backscattered light of the irradiating beam during exposure. Samples of young bovine eyes were exposed in vitro using single pulses ranging from 3 μs to 50 μs. Using the viability assay calcein-AM the ED50 threshold for cell death was determined and compared to the threshold for bubble formation. We also set up a detection system on our slit lamp adapted scanning system in order to determine the feasibility of monitoring threshold RPE damage during selective laser treatment in vivo. Intracellular cavitation was detected as a transient increase in backscattering signal, either of an external probe beam or of the irradiation beam itself. Monitoring with the irradiation beam is both simpler and more sensitive. We found the threshold for bubble formation to coincide with the threshold for cell damage for pulse durations up to 20 μs, suggesting that cavitation is the main mechanism of cell damage. For pulse widths longer than 20 μs, the cell damage mechanism appears to be increasingly thermal as the two thresholds diverge. We conclude that bubble detection can be used to monitor therapeutic endpoint for pulse durations up to 20 μs (or equivalent dwell time in a scanning approach). We have integrated a detection module into our slit lamp adapted laser scanner in order to determine threshold RPE damage during selective laser treatment in vivo.

Proceedings Article | 27 June 2002 Paper

Selective damage of pigmented cells by means of a rapidly scanned cw laser beam

Ralf Brinkmann, Norbert Koop, Mustafa Oezdemir, Clemens Alt, Georg Schuele, Charles Lin, Reginald Birngruber

Proceedings Volume 4617, (2002) https://doi.org/10.1117/12.472538

KEYWORDS: Laser damage threshold, Retina, Laser scanners, Pulsed laser operation, Continuous wave operation, Eye, Laser tissue interaction, Luminescence, Angiography, Scanners

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Proceedings Article | 13 June 2002 Paper

In-vivo and in-vitro selective targeting of the retinal pigment epithelium using a laser-scanning device

Clemens Alt, Carsten Framme, Susanne Schnell, Georg Schuele, Ralf Brinkmann, Charles Lin

Proceedings Volume 4611, (2002) https://doi.org/10.1117/12.470607

KEYWORDS: Angiography, In vitro testing, Retina, Eye, Laser coagulation, In vivo imaging, Continuous wave operation, Lamps, Phase modulation, Laser therapeutics

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Showing 5 of 10 publications

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