Dosimetric properties of a flattening filter-free 6-MV photon beam: a Monte Carlo study |
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Authors: | Mesbahi Asghar Mehnati Parinaz Keshtkar Ahmad Farajollahi Alireza |
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Institution: | (1) Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Attare Nishabouri Street, Tabriz, Iran |
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Abstract: | Purpose The dosimetric features of an unflattened 6-MV photon beam of an Elekta SL-25 linac was calculated by the Monte Carlo (MC)
method.
Material and methods The head of the Elekta SL-25 linac was simulated using the MCNP4C MC code. The accuracy of the model was evaluated using measured
dosimetric features, including depth dose values and dose profiles in a water phantom. The flattening filter was then removed,
and beam dosimetric properties were calculated by the MC method and compared with those of the flattened photon beam.
Results Our results showed a significant (twofold) increase in the dose rate for all field sizes. Also, the photon beam spectra for
an unflattened beam were softer, which led to a steeper reduction in depth doses. The decrease in the out-of-field dose and
increase in the contamination electrons and a buildup region dose were the other consequences of removing the flattening filter.
Conclusion Our study revealed that, for recent radiotherapy techniques, the use of multileaf collimators for beam shaping removing the
flattening filter could offer some advantages, including an increased dose rate and decreased out-of-field dose. |
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Keywords: | Flattening filter-free Unflattened photon beam Elekta SL-25 Monte Carlo simulation |
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