Study on High Density Scintillators and Multi-energy Windows for Improving I-131 Gamma Image Quality: Monte Carlo Simulation Approach
- Authors
- Kim, Minho; Bae, Jae Keon; Hong, Bong Hwan; Kim, Kyeong Min; Lee, Wonho
- Issue Date
- 2월-2019
- Publisher
- KOREAN PHYSICAL SOC
- Keywords
- Iodine-131; Gamma-camera; Monte Carlo simulation; Scatter-Correction; GAGG
- Citation
- JOURNAL OF THE KOREAN PHYSICAL SOCIETY, v.74, no.3, pp.305 - 311
- Indexed
- SCIE
SCOPUS
KCI
- Journal Title
- JOURNAL OF THE KOREAN PHYSICAL SOCIETY
- Volume
- 74
- Number
- 3
- Start Page
- 305
- End Page
- 311
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/68208
- DOI
- 10.3938/jkps.74.305
- ISSN
- 0374-4884
- 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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