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Proceedings Paper

Comparing experimental measurements of x-ray detector responses with Monte Carlo predictions: figures of merit and model development
Author(s): Nahush Rao; Melanie Freed; Aldo Badano
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Paper Abstract

Thalium-activated Cesium Iodide (CsI:Tl) scintillator screens coupled with optical readout arrays are currently the most commonly implemented detection method for digital x-ray imaging. The development of Monte Carlo code to provide detailed simulations of detectors has created the need to quantitatively compare Monte Carlo simulated versus experimentally measured point-response functions (PRFs) for validation. MANTIS is a Monte Carlo code developed for the detailed simulation of columnar CsI scintillator screens. In previous work we have validated the ability of MANTIS to reliably predict experimental PRFs and formulated an analytical model of CsI detector response that generates a PRF comparable to that of MANTIS in less than one millionth of the computation time. At the same time, these results demonstrated the need for optimization of MANTIS input parameters and the method for quantitatively comparing Monte Carlo generated PRFs with experimental data. In this study, we explore the figure-of-merit (FOM) used to compare MANTIS and experimental PRFs and the parameter space of the MANTIS inputs. We used high-resolution PRFs experimentally measured using a 30-μm pinhole arrangement. Multiple sets of simulated PRFs based on partial knowledge of the experimental setup and CsI:Tl screen structures have been produced to compare with the experimental measurements pertaining to a screen with a thickness of 170 μm, an x-ray energy spectrum of 40 kVp, and two x-ray beam incidence angles of 0 and 45 degrees. Input parameters of the Monte Carlo code that were not fixed by the experimental setup or previous validation results were varied to produce the different simulated PRFs. We introduced different FOMs to compare simulated and experimental PRFs and used these FOMs to fine-tune MANTIS models to best represent a particular screen design.

Paper Details

Date Published: 23 March 2010
PDF: 9 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 762252 (23 March 2010); doi: 10.1117/12.845192
Show Author Affiliations
Nahush Rao, U.S. Food and Drug Administration (United States)
Stanford Univ. (United States)
Melanie Freed, U.S. Food and Drug Administration (United States)
Univ. of Maryland, College Park (United States)
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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