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Monte Carlo estimation of electron contamination in a 18 MV clinical photon beam
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M. Allahverdi   , M. Zabihzadeh , M.R. Ay , S.R. Mahdavi , M. Shahriari , A. Mesbahi , H. Alijanzadeh |
| , mohammadreza_ay@tums.ac.ir |
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Abstract: (13591 Views) |
| Background: The electron contamination may
reduce or even diminish the skin sparing property of
the megavoltage beam. The detailed characteristics
of contaminant electrons are presented for different
field sizes and cases. Materials and Methods: The
Monte Carlo code, MCNPX, has been used to
simulate 18 MV photon beam from a Varian
Linac-2300 accelerator. All dose measurements
were carried out using a PTW-MP2 scanner with an
ionization chamber (0.6 CC) at the water phantom.
Results: The maximum electron contaminant dose at
the surface ranged from 6.1 % for 5 × 5 cm2 to 38.8
% for 40 × 40 cm2 and at the depth of maximum
dose was 0.9 % up to 5.77 % for the 5 × 5 cm2 to the
40 × 40 cm2 field sizes, respectively. The additional
contaminant electron dose at the surface for the field
with tray increased 2.3 % for 10 × 10 cm2, 7.3 % for
20 × 20 cm2, and 21.4 % for 40 × 40 cm2 field size
comparing to the standard field without any
accessories. This increase for field with tray and
shaping block was 5.3 % and 13.3 % for 10 × 10 and
20 × 20 cm2, respectively, while, the electron
contamination decreased for the fields with wedge,
i.e. 2.2 % for the 10 × 10 cm2 field. Conclusion: The
results have provided more comprehensive knowledge
of the high-energy clinical beams and may be
useful to develop the accurate treatment planning
systems capable of taking the electron contamination
in to account. Iran. J. Radiat. Res., 2011 9(1): 15-28 |
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| Keywords: Monte Carlo simulation, MV photon beam, electron contamination, relative absorbed dose. |
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Full-Text [PDF 282 kb]
(4261 Downloads)
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Type of Study: Original Research |
Subject:
Radiation Biology
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