Mr. Andreas Keil Profile

Andreas Keil

at SynView GmbH

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Author

Publications (7)

Proceedings Article | 9 May 2012 Paper

Stand-off real-time synthetic imaging at mm-wave frequencies

Matthias Kahl, Andreas Keil, Joern Peuser, Torsten Loeffler, Martin Paetzold, Andreas Kolb, Thorsten Sprenger, Bernd Hils, Peter Haring Bolívar

Proceedings Volume 8362, 836208 (2012) https://doi.org/10.1117/12.919104

KEYWORDS: Imaging systems, Mirrors, Transmitters, Real time imaging, Receivers, Terahertz radiation, Image resolution, Reconstruction algorithms, Data acquisition, Specular reflections

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Proceedings Article | 26 May 2011 Paper

300 GHz imaging with 8 meter stand-off distance and one-dimensional synthetic image reconstruction

Andreas Keil, Torsten Loeffler, Holger Quast, Viktor Krozer, Jørgen Dall, Anders Kusk, Vitaliy Zhurbenko, Thomas Jensen, Peter de Maagt

Proceedings Volume 8022, 80220A (2011) https://doi.org/10.1117/12.886847

KEYWORDS: Imaging systems, Mirrors, Cameras, Connectors, Terahertz radiation, Transmitters, Receivers, Image restoration, Millimeter wave imaging, Metals

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Proceedings Article | 17 March 2011 Paper

Analysis of vertical and horizontal circular C-arm trajectories

A. Maier, J.-H. Choi, A. Keil, C. Niebler, M. Sarmiento, A. Fieselmann, G. Gold, S. Delp, R. Fahrig

Proceedings Volume 7961, 796123 (2011) https://doi.org/10.1117/12.878502

KEYWORDS: Calibration, Sensors, Computed tomography, Optical tracking, Error analysis, Cameras, Medicine, Silver, Matrices, Reconstruction algorithms

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C-arm angiography systems offer great flexibility in the acquisition of trajectories for computed tomography. Theoretically, these systems are able to scan patients while standing in an upright position. This would allow novel insights into structural changes of the human anatomy while weight bearing. However, this would require a scan on a horizontal trajectory parallel to the ground floor which is currently not supported by standard C-arm CT acquisition protocols. In this paper, we compared the standard vertical and the new horizontal scanning trajectories by analysis of the source positions and source to detector distances during the scan. We employed a C-arm calibration phantom to compute the exact scan geometry. Based on the analysis of the projection matrices, we computed the source position in 3D and the source to detector distance for each projection. We then used the calibrated scan geometries to reconstruct the calibration phantom. Based on this reconstruction in comparison to the ideal phantom geometry we also evaluated the geometric reconstruction error. As expected, both the vertical and the horizontal scan trajectories exhibit a significant C-arm "wobble". But in both kinds of trajectories, the reproducibility over several scans was comparable. We were able to reconstruct the calibration phantom with satisfactory geometric reconstruction accuracy. With a reconstruction error of 0.2 mm, we conclude that horizontal C-arm scans are possible and show properties similar to those of vertical C-arm scans. The remaining challenge is compensation for the involuntary movement of the standing subject during a weight-bearing acquisition. We investigated this using an optical tracking system and found that the average movement at the knee while standing upright for 5 seconds is between 0.42 mm and 0.54 mm, and goes up to as much as 12 mm when the subject is holding a 60° squat. This involuntary motion is much larger than the reconstruction accuracy. Hence, we expect artifacts in reconstructions to be significant for upright positions, and overwhelming in squat positions if no motion correction is applied.

Proceedings Article | 27 April 2010 Paper

THz all-electronic 3D imaging for safety and security applications

Bernd Fischer, Yaël Demarty, Markus Schneider, Torsten Löffler, Andreas Keil, Holger Quast

Proceedings Volume 7671, 767111 (2010) https://doi.org/10.1117/12.851434

KEYWORDS: Safety, Reflectivity, Terahertz radiation, Stereoscopy, Information security, Head, Imaging spectroscopy, Data acquisition, Photography, Spatial resolution

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Proceedings Article | 14 March 2009 Paper

Blind motion compensation for positron-emission-tomography

Moritz Blume, Andreas Keil, Nassir Navab, Magdalena Rafecas

Proceedings Volume 7258, 72580T (2009) https://doi.org/10.1117/12.811118

KEYWORDS: Reconstruction algorithms, Medical imaging, Detection and tracking algorithms, Physics, Current controlled current source, Positron emission tomography, Image restoration, Optimization (mathematics), Mathematical modeling, Motion models

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Proceedings Article | 11 March 2008 Paper

Semi-automatic detection of Gd-DTPA-saline filled capsules for colonic transit time assessment in MRI

Christian Harrer, Sonja Kirchhoff, Andreas Keil, Chlodwig Kirchhoff, Thomas Mussack, Andreas Lienemann, Maximilian Reiser, Nassir Navab

Proceedings Volume 6914, 69143K (2008) https://doi.org/10.1117/12.769867

KEYWORDS: Magnetic resonance imaging, Image segmentation, Principal component analysis, Image resolution, Clouds, Human-machine interfaces, Image classification, Pathology, Ionizing radiation, Colon

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Proceedings Article | 1 October 1998 Paper

Complexity and PSNR comparison of several fast motion estimation algorithms for MPEG-4

Peter Kuhn, Georg Diebel, Stephan Herrmann, Andreas Keil, Hubert Mooshofer, Andre Kaup, Robert Mayer, Walter Stechele

Proceedings Volume 3460, (1998) https://doi.org/10.1117/12.323203

KEYWORDS: Motion estimation, Video, Video coding, Motion analysis, Chlorine, Very large scale integration, Video compression, Computer programming, Visualization, Statistical analysis

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Showing 5 of 7 publications

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