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Penumbra width determination of single beam and 201 beams of Gamma Knife machine model 4C using Monte Carlo simulation

Published online by Cambridge University Press:  11 September 2018

Atefeh Mahmoudi ,
Alireza Shirazi ,
Ghazale Geraily ,
Tahereh Hadisi nia ,
Masoume Bakhshi  and
Maryam Maleki
Atefeh Mahmoudi
Affiliation:
Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Islamic Republic of Iran
Alireza Shirazi*
Affiliation:
Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Islamic Republic of Iran
Ghazale Geraily*
Affiliation:
Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Islamic Republic of Iran
Tahereh Hadisi nia
Affiliation:
Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Islamic Republic of Iran
Masoume Bakhshi
Affiliation:
Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Islamic Republic of Iran
Maryam Maleki
Affiliation:
Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Isfahan University of Medical Sciences, Islamic Republic of Iran
*
Author for correspondence: Ghazale Geraily, Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Iran. Email: [email protected]
Author for correspondence: Ghazale Geraily, Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Iran. Email: [email protected]
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Abstract

Background

One of the stereotactic radiosurgery techniques is Gamma Knife radiosurgery, in which intracranial lesions that are inaccessible or inappropriate for surgery are treated using 201 cobalt-60 sources in one treatment session. In this conformal technique, the penumbra width, which results in out-of-field dose in tumour-adjacent normal tissues should be determined accurately. The aim of this study is to calculate the penumbra widths of single and 201 beams for different collimator sizes of Gamma Knife machine model 4C using EGSnrc/BEAMnrc Monte Carlo simulation code and comparison the results with EBT3 film dosimetry data.

Methods and materials

In this study, simulation of Gamma Knife machine model 4C was performed based on the Monte Carlo codes of EGSnrc/BEAMnrc. To investigate the physical penumbra width (80−20%), the single beam and 201 beams profiles were obtained using EGSnrc/DOSXYZnrc code and EBT3 films located at isocentre point in a spherical Plexiglas head phantom.

Results

Based on the results, the single beam penumbra widths obtained from simulation data for 4, 8, 14 and 18 mm collimator sizes along X axis were 0·75, 0·77, 0·90 and 0·92 mm, respectively. The data for 201 beams obtained from simulation were 2·61, 4·80, 7·92 and 9·81 mm along X axis and 1·31, 1·60, 1·91 and 2·14 mm along Z axis and from film dosimetry were 3·21, 4·90, 8·00 and 10·61 mm along X axis and 1·22, 1·69, 2·01 and 2·25 mm along Z axis, respectively.

Conclusion

The differences between measured and simulated penumbra widths are in an acceptable range. However, for more precise measurement in the penumbra region in which dose gradient is high, Monte Carlo simulation is recommended.

Keywords

Gamma Knife model 4CMonte Carlo simulationphysical penumbraEBT3 film
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 18 , Issue 1 , March 2019 , pp. 82 - 87
Copyright
© Cambridge University Press 2018 

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Footnotes

Cite this article: Mahmoudi A, Shirazi A, Geraily G, Hadisi nia T, Bakhshi M, Maleki M. (2019) Penumbra width determination of single beam and 201 beams of Gamma Knife machine model 4C using Monte Carlo simulation. Journal of Radiotherapy in Practice18: 82–87. doi: 10.1017/S1460396918000407

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