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Title: Monte Carlo study on the imaging performance of powder Lu{sub 2}SiO{sub 5}:Ce phosphor screens under x-ray excitation: Comparison with Gd{sub 2}O{sub 2}S:Tb screens

Abstract

Lu{sub 2}SiO{sub 5}:Ce (LSO) scintillator is a relatively new luminescent material which has been successfully applied in positron emission tomography systems. Since it has been recently commercially available in powder form, it could be of value to investigate its performance for use in x-ray projection imaging as both physical and scintillating properties indicate a promising material for such applications. In the present study, a custom and validated Monte Carlo simulation code was used in order to examine the performance of LSO, under diagnostic radiology (mammography and general radiography) conditions. The Monte Carlo code was based on a model using Mie scattering theory for the description of light attenuation. Imaging characteristics, related to image brightness, spatial resolution and noise of LSO screens were predicted using only physical parameters of the phosphor. The overall performance of LSO powder phosphor screens was investigated in terms of the: (i) quantum detection efficiency (ii) emitted K-characteristic radiation (iii) luminescence efficiency (iv) modulation transfer function (v) Swank factor and (vi) zero-frequency detective quantum efficiency [DQE(0)]. Results were compared to the traditional rare-earth Gd{sub 2}O{sub 2}S:Tb (GOS) phosphor material. The relative luminescence efficiency of LSO phosphor was found inferior to that of GOS. This is due tomore » the lower intrinsic conversion efficiency of LSO (0.08 instead of 0.15 of GOS) and the relatively high light extinction coefficient m{sub ext} of this phosphor (0.239 {mu}m{sup -1} instead of 0.218 {mu}m{sup -1} for GOS). However, the property of increased light extinction combined with the rather sharp angular distribution of scattered light photons (anisotropy factor g=0.624 for LSO instead of 0.494 for GOS) reduce lateral light spreading and improve spatial resolution. In addition, LSO screens were found to exhibit better x-ray absorption as well as higher signal to noise transfer properties in the energy range from 18 keV up to 50.2 keV (e.g. DQE(0)=0.62 at 18 keV and for 34 mg/cm{sup 2}, instead of 0.58 for GOS). The results indicate that certain optical properties of LSO (optical extinction coefficient, scattering anisotropy factor) combined with the relatively high x-ray coefficients, make this material a promising phosphor which, under appropriate conditions, could be considered for use in x-ray projection imaging detectors.« less

Authors:
; ; ; ;  [1];  [2];  [2]
  1. Department of Medical Physics, Faculty of Medicine, University of Patras, 265 00 Patras (Greece)
  2. (Greece)
Publication Date:
OSTI Identifier:
20951303
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 5; Other Information: DOI: 10.1118/1.2724065; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BIOMEDICAL RADIOGRAPHY; COMPUTERIZED SIMULATION; IMAGES; LUMINESCENCE; MAMMARY GLANDS; MONTE CARLO METHOD; NOISE; PHOSPHORS; POSITRON COMPUTED TOMOGRAPHY; QUANTUM EFFICIENCY; SOLID SCINTILLATION DETECTORS; SPATIAL RESOLUTION

Citation Formats

Liaparinos, Panagiotis F., Kandarakis, Ioannis S., Cavouras, Dionisis A., Delis, Harry B., Panayiotakis, George S., Department of Medical Instruments Technology, Technological Educational Institute, 122 10 Athens, and Department of Medical Physics, Faculty of Medicine, University of Patras, 265 00 Patras. Monte Carlo study on the imaging performance of powder Lu{sub 2}SiO{sub 5}:Ce phosphor screens under x-ray excitation: Comparison with Gd{sub 2}O{sub 2}S:Tb screens. United States: N. p., 2007. Web. doi:10.1118/1.2724065.
Liaparinos, Panagiotis F., Kandarakis, Ioannis S., Cavouras, Dionisis A., Delis, Harry B., Panayiotakis, George S., Department of Medical Instruments Technology, Technological Educational Institute, 122 10 Athens, & Department of Medical Physics, Faculty of Medicine, University of Patras, 265 00 Patras. Monte Carlo study on the imaging performance of powder Lu{sub 2}SiO{sub 5}:Ce phosphor screens under x-ray excitation: Comparison with Gd{sub 2}O{sub 2}S:Tb screens. United States. doi:10.1118/1.2724065.
Liaparinos, Panagiotis F., Kandarakis, Ioannis S., Cavouras, Dionisis A., Delis, Harry B., Panayiotakis, George S., Department of Medical Instruments Technology, Technological Educational Institute, 122 10 Athens, and Department of Medical Physics, Faculty of Medicine, University of Patras, 265 00 Patras. Tue . "Monte Carlo study on the imaging performance of powder Lu{sub 2}SiO{sub 5}:Ce phosphor screens under x-ray excitation: Comparison with Gd{sub 2}O{sub 2}S:Tb screens". United States. doi:10.1118/1.2724065.
@article{osti_20951303,
title = {Monte Carlo study on the imaging performance of powder Lu{sub 2}SiO{sub 5}:Ce phosphor screens under x-ray excitation: Comparison with Gd{sub 2}O{sub 2}S:Tb screens},
author = {Liaparinos, Panagiotis F. and Kandarakis, Ioannis S. and Cavouras, Dionisis A. and Delis, Harry B. and Panayiotakis, George S. and Department of Medical Instruments Technology, Technological Educational Institute, 122 10 Athens and Department of Medical Physics, Faculty of Medicine, University of Patras, 265 00 Patras},
abstractNote = {Lu{sub 2}SiO{sub 5}:Ce (LSO) scintillator is a relatively new luminescent material which has been successfully applied in positron emission tomography systems. Since it has been recently commercially available in powder form, it could be of value to investigate its performance for use in x-ray projection imaging as both physical and scintillating properties indicate a promising material for such applications. In the present study, a custom and validated Monte Carlo simulation code was used in order to examine the performance of LSO, under diagnostic radiology (mammography and general radiography) conditions. The Monte Carlo code was based on a model using Mie scattering theory for the description of light attenuation. Imaging characteristics, related to image brightness, spatial resolution and noise of LSO screens were predicted using only physical parameters of the phosphor. The overall performance of LSO powder phosphor screens was investigated in terms of the: (i) quantum detection efficiency (ii) emitted K-characteristic radiation (iii) luminescence efficiency (iv) modulation transfer function (v) Swank factor and (vi) zero-frequency detective quantum efficiency [DQE(0)]. Results were compared to the traditional rare-earth Gd{sub 2}O{sub 2}S:Tb (GOS) phosphor material. The relative luminescence efficiency of LSO phosphor was found inferior to that of GOS. This is due to the lower intrinsic conversion efficiency of LSO (0.08 instead of 0.15 of GOS) and the relatively high light extinction coefficient m{sub ext} of this phosphor (0.239 {mu}m{sup -1} instead of 0.218 {mu}m{sup -1} for GOS). However, the property of increased light extinction combined with the rather sharp angular distribution of scattered light photons (anisotropy factor g=0.624 for LSO instead of 0.494 for GOS) reduce lateral light spreading and improve spatial resolution. In addition, LSO screens were found to exhibit better x-ray absorption as well as higher signal to noise transfer properties in the energy range from 18 keV up to 50.2 keV (e.g. DQE(0)=0.62 at 18 keV and for 34 mg/cm{sup 2}, instead of 0.58 for GOS). The results indicate that certain optical properties of LSO (optical extinction coefficient, scattering anisotropy factor) combined with the relatively high x-ray coefficients, make this material a promising phosphor which, under appropriate conditions, could be considered for use in x-ray projection imaging detectors.},
doi = {10.1118/1.2724065},
journal = {Medical Physics},
number = 5,
volume = 34,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}