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Assessment of portal image resolution improvement using an external aluminum target and polystyrene electron filter

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Author(s)
Jonggeun BaekHyungdong KimByungyong KimYoungkee OhHyunsoo Jang
Keimyung Author(s)
Oh, Young Kee
Department
Dept. of Radiation Oncology (방사선종양학)
Journal Title
Radiation Oncology
Issued Date
2019
Volume
14
Issue
1
Keyword
Low-Z targetPortal imagingSpatial resolutionContrast resolutionContrast and details
Abstract
Background:
In this study, an external 8mm thick aluminum target was installed on the upper accessory tray mount of a medical linear accelerator head. The purpose of this study was to determine the effects of the external aluminum target beam (Al-target beam) on the portal image quality by analyzing the spatial and contrast resolutions. In addition, the image resolutions with the Al-target beams were compared with those of conventional 6 megavoltage (MV) images.

Methods:
The optimized Al-target beam was calculated using Monte Carlo simulations. To validate the simulations, the percentage depth dose and lateral profiles were measured and compared with the modeled dose distributions. A PTW resolution phantom was used for imaging to assess the image resolution. The spatial resolution was quantified by determining the modulation transfer function. The contrast resolution was determined by a fine contrast difference between the 27 measurement areas. The spatial and contrast resolutions were compared with the those of conventional portal images.

Results:
The measured and calculated percentage depth dose of the Al-target beam were consistent within 1.6%. The correspondence of measured and modelled profiles was evaluated by gamma analysis (3%, 3mm) and all gamma values inside the field were less than one. The critical spatial frequencies (f50) of the images obtained with the Al-target beam and conventional imaging beam were 0.745 lp/mm and 0.451 lp/mm, respectively. The limiting spatial frequencies (f10) for the Al-target beamimage and the conventional portal image were 2.39 lp/mmand 1.82 lp/mm, respectively. The Al-target beam resolved the smaller and lower contrast objects better than that of the MV photon beam.

Conclusion:
The Al-target beams generated by the simple target installation method provided better spatial and contrast resolutions than those of the conventional 6 MV imaging beam
Keimyung Author(s)(Kor)
오영기
Publisher
School of Medicine (의과대학)
Citation
Jonggeun Baek et al. (2019). Assessment of portal image resolution improvement using an external aluminum target and polystyrene electron filter. Radiation Oncology, 14(1), 70–70. doi: 10.1186/s13014-019-1274-4
Type
Article
ISSN
1748-717X
Source
https://ro-journal.biomedcentral.com/articles/10.1186/s13014-019-1274-4
DOI
10.1186/s13014-019-1274-4
URI
https://kumel.medlib.dsmc.or.kr/handle/2015.oak/41994
Appears in Collections:
1. School of Medicine (의과대학) > Dept. of Radiation Oncology (방사선종양학)
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