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Study of unflattened photon beams shaped by multileaf collimator using BEAMnrc code

Published online by Cambridge University Press:  01 November 2016

Ankit kajaria ,
Neeraj Sharma ,
Shiru Sharma ,
Satyajit Pradhan ,
Abhijit Mandal  and
Lalit M. Aggarwal
Ankit kajaria*
Affiliation:
School of Biomedical Engineering, Indian Institute of Technology (BHU) Varanasi, Varanasi, Uttar Pradesh, India
Neeraj Sharma
Affiliation:
School of Biomedical Engineering, Indian Institute of Technology (BHU) Varanasi, Varanasi, Uttar Pradesh, India
Shiru Sharma
Affiliation:
School of Biomedical Engineering, Indian Institute of Technology (BHU) Varanasi, Varanasi, Uttar Pradesh, India
Satyajit Pradhan
Affiliation:
Department of Radiotherapy and Radiation Medicine, Institute of Medical Science (BHU) Varanasi, Varanasi, Uttar Pradesh, India
Abhijit Mandal
Affiliation:
Department of Radiotherapy and Radiation Medicine, Institute of Medical Science (BHU) Varanasi, Varanasi, Uttar Pradesh, India
Lalit M. Aggarwal
Affiliation:
Department of Radiotherapy and Radiation Medicine, Institute of Medical Science (BHU) Varanasi, Varanasi, Uttar Pradesh, India
*
Correspondence to: Ankit kajaria, School of Biomedical Engineering, Indian Institute of Technology (BHU) Varanasi, Varanasi, Uttar Pradesh, India. Tel: 917607066152; E-mail: akajaria.rs.bme12@itbhu.ac.in
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Abstract

Purpose

In our study basic dosimetric properties of a flattening filter free 6 MV photon beam shaped by multileaf collimators (MLC) is examined using the Monte Carlo (MC) method.

Methods and Materials

BEAMnrc code was used to make a MC simulation model for 6 MV photon beam based on Varian Clinic 600 unique performance linac, operated with and without a flattening filter in beam line. Dosimetric features including central axis depth dose, beam profiles, photon and electron spectra were calculated and compared for flattened and unflattened cases.

Results

Dosimetric field size and penumbra were found to be smaller for unflattened beam, and the decrease in field size was less for MLC shaped in comparison with jaw-shaped unflattened beam. Increase in dose rate of >2·4 times was observed for unflattened beam indicating a shorter beam delivery time for treatment. MLC leakage was found to decrease significantly when the flattening filter was removed from the beam line. The total scatter factor showed slower deviation with field sizes for unflattened beam indicating a reduced head scatter.

Conclusions

Our study demonstrated that improved accelerator characteristics can be achieved by removing flattening filter from beam line.

Keywords

accelerator characteristicsMonte Carlo simulationmultileaf collimatorunflattened photon beam
Type
Technical Note
Information
Journal of Radiotherapy in Practice , Volume 15 , Issue 4 , December 2016 , pp. 392 - 401
Copyright
© Cambridge University Press 2016 

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