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Proceedings Paper

Scatter rejection methods in megavoltage imaging with an amorphous-silicon flat-panel array
Author(s): Burkhard A. Groh; Lothar Spies; Bernd M. Hesse; Thomas Bortfeld
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Paper Abstract

X-ray scattering in megavoltage portal imaging becomes more of an issue when quantitative results are needed. This is the case in megavoltage computed tomography (MVCT) and transit dosimetry, where the absorbed dose delivered to the patient is to be reconstructed. Although sensor arrays based on amorphous silicon (a-Si) photodiodes show promising results for this application, the scatter problem has so far not been examined. In this paper portal scatter distributions are calculated by means of Monte-Carlo (MC) simulations for typical clinical parameters. The aim of the MC simulations is to design a detector which is able to reject photons and electrons scattered by the phantom. As expected the analysis of the spectrum shows that multiply scattered photons can be differentiated from singly scattered photons by means of their energy. The MC results indicate that by using a detector with a high-Z conversion plate combined with a moderately thick phosphor screen a significant fraction of low energy scattered photons and most electrons can be rejected. However, to reduce the scatter signal further a software correction method based on a dedicated scatter model is still necessary.

Paper Details

Date Published: 25 April 2000
PDF: 8 pages
Proc. SPIE 3977, Medical Imaging 2000: Physics of Medical Imaging, (25 April 2000); doi: 10.1117/12.384537
Show Author Affiliations
Burkhard A. Groh, Deutsches Krebsforschungszentrum (Germany)
Lothar Spies, Deutsches Krebsforschungszentrum (Germany)
Bernd M. Hesse, Deutsches Krebsforschungszentrum (Germany)
Thomas Bortfeld, Deutsches Krebsforschungszentrum (Germany)

Published in SPIE Proceedings Vol. 3977:
Medical Imaging 2000: Physics of Medical Imaging
James T. Dobbins III; John M. Boone, Editor(s)

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