Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/115504
Type: Journal article
Title: A quality assurance program for an amorphous silicon electronic portal imaging device using in-house developed phantoms: a method development for dosimetry purpose
Author: Jomehzadeh, A.
Shokrani, P.
Mohammadi, M.
Amouheidari, A.
Citation: INTERNATIONAL JOURNAL OF RADIATION RESEARCH, 2014; 12(3):257-264
Publisher: Novin Medical Radiation Institute
Issue Date: 2014
ISSN: 2322-3243
2345-4229
Statement of
Responsibility: 
A. Jomehzadeh, P. Shokrani, M. Mohammadi, A. Amouheidari
Abstract: Background: Electronic portal imaging devices (EPIDs) play an important role in radiation therapy portal imaging, geometric and dosimetric verifications. A successful utilization of EPIDs for imaging and dosimetric purposes requires a reliable quality control process routine to be carried out regularly. In this study, two in-house phantoms were developed and analyzed for implementation in a quality assurance program for dosimetry purposes. Materials and Methods: An amorphous silicon (a-Si) imager (OptiVue500) was used. A low contrast resolution phantom and an image quality phantom were constructed and implemented. Low contrast resolution of the EPID was evaluated by counting the number of holes detectable in the image of phantom using human observers and a software. The image quality phantom was used for modulation transfer function, contrast to noise ratio and noise level evaluations. This phantom contains five sets of high-contrast rectangular bar patterns of variable spatial frequencies and six uniform regions. Results: Although the manual low contrast resolution method was observer-dependent and insensitive to artifacts, the automatic method was robust and fully objective but sensitive to artifacts. The critical frequency values for 6 and 18 MV were 0.3558±0.006 lp/mm and 0.2707±0.006 lp/mm respectively. The contrast-to-noise ratio was found to be ~ 240% higher for 6 MV compared to 18 MV. Conclusion: The developed phantoms provide a convenient process for periodic performance of an EPID. These phantoms are independent of the EPID system and provide robust tools for continuous monitoring of image quality parameters as well as dosimetric parameters.
Keywords: Electronic portal imaging device; quality assurance; phantom
Rights: Copyright Novin Medical Radiation Institute Jul 2014
Published version: http://ijrr.com/article-1-1284-en.html
Appears in Collections:Aurora harvest 8
Medicine publications

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