Study on High Density Scintillators and Multi-energy Windows for Improving I-131 Gamma Image Quality: Monte Carlo Simulation Approach

Minho Kim, Jae Keon Bae, Bong Hwan Hong, Kyeong Min Kim, Won Ho Lee

Research output: Contribution to journalArticle

Abstract

An energy window with a gamma peak centered at 364 keV (86%) is usually used for I-131 imaging. However, the image performance indexes such as image count, scatter fraction (SF), spatial resolution (SR) obtained using a conventional gamma camera, which uses a 3/8-in sodium iodide scintillator, are poor mainly due to its low detection efficiency. In this study, we investigated the feasibility of using a higher energy peak (637 and 723 keV) for the energy window to obtain a better imaging performance compared with the conventional I-131 imaging method. GATE (v7.0), which is based on Monte Carlo method, was used for performing simulations. A clinical gamma camera, SYMBIA-T2 (Siemens), was mounted on a NaI scintillator in the simulation. A GAGG scintillator was also realized for effective detection of high energy gamma, in addition to using high energy (HE) and ultrahigh energy (UHE) collimators. We obtained I-131 planar images through the conventionally used window method (364 keV ± 10%). The high-energy gamma ray of I 131 (637 and 723 keV) have been additionally used for improving image performance. The scatter correction method was applied to images for suppressing scatter due to high-energy gamma rays. Various indexes are used for validating image performance such as SR, SF, and contrast-to-noise ratio. High-energy gamma rays could be used to increase the image counts, but the other image performances were degraded compared to the scatter-corrected 364 keV images (SF of 6.33 - 27.73%; SR of 0.93 - 6.02%). The UHE collimator was useful in obtaining a better spatial resolution and suppressing scatter components compared with the HE collimator. However, it did not exhibit a sufficient image performance to be considered as a replacement for the HE collimator. In order to use the high-energy gamma rays of I-131 (637 and 723 keV), it is necessary to design a new collimator to control penetration and improve resolution, instead of using a UHE collimator. Furthermore, scatter correction methods also need to be optimized.

Original languageEnglish
Pages (from-to)305-311
Number of pages7
JournalJournal of the Korean Physical Society
Volume74
Issue number3
DOIs
Publication statusPublished - 2019 Feb 1

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scintillation counters
collimators
simulation
energy
spatial resolution
gamma rays
cameras
GARP Atlantic Tropical Experiment
sodium iodides
Monte Carlo method
penetration

Keywords

  • GAGG
  • Gamma-camera
  • Iodine-131
  • Monte Carlo simulation
  • Scatter-Correction

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Study on High Density Scintillators and Multi-energy Windows for Improving I-131 Gamma Image Quality : Monte Carlo Simulation Approach. / Kim, Minho; Bae, Jae Keon; Hong, Bong Hwan; Kim, Kyeong Min; Lee, Won Ho.

In: Journal of the Korean Physical Society, Vol. 74, No. 3, 01.02.2019, p. 305-311.

Research output: Contribution to journalArticle

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abstract = "An energy window with a gamma peak centered at 364 keV (86{\%}) is usually used for I-131 imaging. However, the image performance indexes such as image count, scatter fraction (SF), spatial resolution (SR) obtained using a conventional gamma camera, which uses a 3/8-in sodium iodide scintillator, are poor mainly due to its low detection efficiency. In this study, we investigated the feasibility of using a higher energy peak (637 and 723 keV) for the energy window to obtain a better imaging performance compared with the conventional I-131 imaging method. GATE (v7.0), which is based on Monte Carlo method, was used for performing simulations. A clinical gamma camera, SYMBIA-T2 (Siemens), was mounted on a NaI scintillator in the simulation. A GAGG scintillator was also realized for effective detection of high energy gamma, in addition to using high energy (HE) and ultrahigh energy (UHE) collimators. We obtained I-131 planar images through the conventionally used window method (364 keV ± 10{\%}). The high-energy gamma ray of I 131 (637 and 723 keV) have been additionally used for improving image performance. The scatter correction method was applied to images for suppressing scatter due to high-energy gamma rays. Various indexes are used for validating image performance such as SR, SF, and contrast-to-noise ratio. High-energy gamma rays could be used to increase the image counts, but the other image performances were degraded compared to the scatter-corrected 364 keV images (SF of 6.33 - 27.73{\%}; SR of 0.93 - 6.02{\%}). The UHE collimator was useful in obtaining a better spatial resolution and suppressing scatter components compared with the HE collimator. However, it did not exhibit a sufficient image performance to be considered as a replacement for the HE collimator. In order to use the high-energy gamma rays of I-131 (637 and 723 keV), it is necessary to design a new collimator to control penetration and improve resolution, instead of using a UHE collimator. Furthermore, scatter correction methods also need to be optimized.",
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