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Proceedings Paper

Monte Carlo simulation of amorphous selenium imaging detectors
Author(s): Yuan Fang; Andreu Badal; Nicholas Allec; Karim S. Karim; Aldo Badano
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Paper Abstract

We present a Monte Carlo (MC) simulation method for studying the signal formation process in amorphous Selenium (a-Se) imaging detectors for design validation and optimization of direct imaging systems. The assumptions and limitations of the proposed and previous models are examined. The PENELOPE subroutines for MC simulation of radiation transport are used to model incident x-ray photon and secondary electron interactions in the photoconductor. Our simulation model takes into account applied electric field, atomic properties of the photoconductor material, carrier trapping by impurities, and bimolecular recombination between drifting carriers. The particle interaction cross-sections for photons and electrons are generated for Se over the energy range of medical imaging applications. Since inelastic collisions of secondary electrons lead to the creation of electron-hole pairs in the photoconductor, the electron inelastic collision stopping power is compared for PENELOPE's Generalized Oscillator Strength model with the established EEDL and NIST ESTAR databases. Sample simulated particle tracks for photons and electrons in Se are presented, along with the energy deposition map. The PENEASY general-purpose main program is extended with custom transport subroutines to take into account generation and transport of electron-hole pairs in an electromagnetic field. The charge transport routines consider trapping and recombination, and the energy required to create a detectable electron-hole pair can be estimated from simulations. This modular simulation model is designed to model complete image formation.

Paper Details

Date Published: 18 March 2010
PDF: 9 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 762214 (18 March 2010); doi: 10.1117/12.844983
Show Author Affiliations
Yuan Fang, Univ. of Waterloo (Canada)
U.S. Food and Drug Administration (United States)
Andreu Badal, U.S. Food and Drug Administration (United States)
Nicholas Allec, Univ. of Waterloo (Canada)
Karim S. Karim, Univ. of Waterloo (Canada)
Aldo Badano, U.S. Food and Drug Administration (United States)

Published in SPIE Proceedings Vol. 7622:
Medical Imaging 2010: Physics of Medical Imaging
Ehsan Samei; Norbert J. Pelc, Editor(s)

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