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Dosimetric properties of fluoroscopic EPID for transit dosimetry

Published online by Cambridge University Press:  30 October 2014

Akbar Anvari ,
Seyed Mahmoud Reza Aghamiri ,
Seyed Rabi Mahdavi ,
Parham Alaei  and
Mohammad Mohammadi
Akbar Anvari*
Affiliation:
Department of Radiation Medicine Engineering, Shahid Beheshti University, Tehran, Iran
Seyed Mahmoud Reza Aghamiri
Affiliation:
Department of Radiation Medicine Engineering, Shahid Beheshti University, Tehran, Iran
Seyed Rabi Mahdavi
Affiliation:
Department of Medical Physics, Iran University of Medical Sciences, Tehran, Iran
Parham Alaei
Affiliation:
Department of Radiation Oncology, University of Minnesota, Minneapolis, Minnesota, USA
Mohammad Mohammadi
Affiliation:
Department of Medical Physics, Royal Adelaide Hospital, Adelaide, SA, Australia
*
Correspondence to: Akbar Anvari, Department of Radiation Medicine Engineering, Shahid Beheshti University, Tehran 19839-63113, Iran. Tel: +98 9196260656. E-mail: [email protected]
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Abstract

The aim of this work was to evaluate dose response of fluoroscopic EPID for transit dosimetry applications. Properties studied included warm up time, build-up thickness evaluation, dose history, linearity, stability, and short and long-term reproducibility of EPID response, as well as field size dependence.

Pixel value matrices of electronic portal images in DICOM format were analysed in central and 8 off axis points using customised written codes in Matlab. In order to do this, nine 26×26 pixel matrices were selected as regions of interest, the regions represented by these arrays were 1×1 and 0·65×0·65 cm2 at the EPID and isocentre level, respectively.

Necessary warm up time for stable operation of EPID is 30 minutes, and there is no need for extra build-up layer to increase the dose response. Linearity tests indicate charged coupled device camera of EPID saturates at 50 cGy level, and does not have linear relationship with dose. Reproducibility and stability of the measurements were excellent and the detector showed same signal with a maximum deviation of <0·3% both in short and long terms. Results of dosimetric evaluation have shown the TheraView fluoroscopic EPID can be used for transit dosimetry purposes.

Keywords

dose responsedosimetryepidportal imaging
Type
Original Articles
Information
Journal of Radiotherapy in Practice , Volume 14 , Issue 1 , March 2015 , pp. 27 - 34
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Copyright
© Cambridge University Press 2014 

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