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Experimental validatıon of peripheral dose distribution of electron beams for eclipse electron Monte Carlo algorithm

Published online by Cambridge University Press:  23 July 2018

Hilal Acar ,
Mustafa Caglar  and
Ayse Y. Altinok
Hilal Acar*
Affiliation:
Department of Radiation Oncology, Istanbul Medipol University, Istanbul, Turkey
Mustafa Caglar
Affiliation:
Department of Radiation Oncology, Istanbul Medipol University, Istanbul, Turkey
Ayse Y. Altinok
Affiliation:
Department of Radiation Oncology, Istanbul Medipol University, Istanbul, Turkey
*
Correspondence to: Assoc Prof. Hilal Acar, Department of Radiation Oncology, Medicine Faculty, Istanbul Medipol University, 34214, Istanbul, Turkey. Tel: +90 (535) 9395365. Fax: 90 (212) 460 70 70. E-mail: hacar@medipol.edu.tr
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Abstract

Aim

The accuracy of two calculation algorithms of the Varian Eclipse treatment planning system (TPS), the electron Monte Carlo algorithm (eMC) and general Gaussian pencil beam algorithm (GGPB) for calculating peripheral dose distribution of electron beams was investigated.

Methods

Peripheral dose measurements were carried out for 6, 9, 12, 15, 18 and 22 MeV electron beams using parallel plate ionisation chamber and EBT3 film in the slab phantom. Measurements were performed for 6×6, 10×10 and 25×25 cm2 cone sizes at dmax of each energy up to 20 cm beyond the field edges. The measured and TPS calculated data were compared.

Results

The TPS underestimated the out-of-field doses. The difference between measured and calculated doses increase with the cone size. For ionisation chamber measurement, the largest deviation between calculated and measured doses is <4·29% using the eMC, but can increase up to 8·72% of the distribution using GGPB. For film measurement, the minimum gamma analysis passing rates between measured and calculated dose distributions for all field sizes and energies used in this study were 91·2 and 74·7% for eMC and GGPB, respectively.

Findings

The use of GGPB for planning large field treatments with 6 MeV could lead to inaccuracies of clinical significance.

Keywords

electron beamseMCGGPB.EBT3 filmperipheral dose distribution
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 17 , Issue 3 , September 2018 , pp. 279 - 288
Copyright
© Cambridge University Press 2018 

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