Measurement of Collimator Scatter Factor for Photon Fields Using Gafchromic EBT2 Film and Ion Chamber

Asgarian Dehkordy, Zeinab. and Atarod, Maryam. and Eini, Fariba. and Hoseini, Seyed Mohammad. and Tahmasebi Birgan, Mohammad Javad. and Chegeni, Nahid. (2016) Measurement of Collimator Scatter Factor for Photon Fields Using Gafchromic EBT2 Film and Ion Chamber. Jundishapur Scientific Medical Journal, 14 (6).

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Background and Objective: In radiotherapy, measurement of the output factor in the air is one of the input parameters for Implementation of treatment planning systems and beam modeling. The aim of this study is to design a mini-phantom and select the appropriate detector for measuring the output factor. Subjects and Methods: In-air output factor was measured for Siemens linear accelerator 6 MV energy and field sizes of 4, 6, 8, 10, 15, 2 cm irradiated by 200MU. Measurements were performed using a Gafchromic film EBT2 and 0.6 cc Farmer ion chamber and then the results were compared with Report of AAPM Therapy Physics Committee Task Group 74. For lateral electron equilibrium and electron contamination removal, two top of the water and Cerrobend were designed for film dosimetry and plexiglass buildup cap for Farmer chamber was applied. Results: The output factor increases with field size, and this increase in Cerrobend top is less than water top and Farmer dosimeter. In comparison between the results reported by TG74 and this study shows that film dosimetry with water top and Farmer chamber have 0.35 and 0.68 mean percentage differences with TG74 respectively and meanwhile the film dosimetry with Cerrobend top presents 1.48 mean percentage differences. Conclusion: EBT2 film with mini phantom made of water as a good alternative to ion chamber dosimeters known as a standard dosimeter especially the film can be used for a wider range of field sizes

Item Type: Article
Subjects: WN Radiology . Diagnostic Imaging
Divisions: Faculty of Medicine > Department of Clinical Sciences > Department of Radiology
Depositing User: zahra bagheri .
Date Deposited: 17 Oct 2017 07:16
Last Modified: 15 May 2018 05:32

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