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Home > 학회활동 > 국제학술지 |
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작성일 : 11-10-10 18:33
| 저 자 |
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Woong Cho et al |
| 제 목 |
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Multisource modeling of flattening filter free „FFF… beam and the optimization of model parameters |
| 학회지명 |
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Medical Physics |
| 권 호 |
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38 (4) |
| 페이지 |
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1931-1942 |
| 년,월 |
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2011-4-1 |
| 링 크 |
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| Abstract |
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Purpose: With the introduction of flattening filter free FFF linear accelerators to radiation oncol-
ogy, new analytical source models for a FFF beam applicable to current treatment planning systems
is needed. In this work, a multisource model for the FFF beam and the optimization of involved
model parameters were designed.
Methods: The model is based on a previous three source model proposed by Yang et al. “A
three-source model for the calculation of head scatter factors,” Med. Phys. 29, 2024–2033 2002.
An off axis ratio OAR of photon fluence was introduced to the primary source term to generate
cone shaped profiles. The parameters of the source model were determined from measured head
scatter factors using a line search optimization technique. The OAR of the photon fluence was
determined from a measured dose profile of a 4040 cm2
field size with the same optimization
technique, but a new method to acquire gradient terms for OARs was developed to enhance the
speed of the optimization process. The improved model was validated with measured dose profiles
from 33to4040 cm2
field sizes at 6 and 10 MV from a TrueBeam™ STx linear accelerator.
Furthermore, planar dose distributions for clinically used radiation fields were also calculated and
compared to measurements using a 2D array detector using the gamma index method.
Results: All dose values for the calculated profiles agreed with the measured dose profiles within
0.5% at 6 and 10 MV beams, except for some low dose regions for larger field sizes. A slight
overestimation was seen in the lower penumbra region near the field edge for the large field sizes
by 1%–4%. The planar dose calculations showed comparable passing rates 98% when the
criterion of the gamma index method was selected to be 3%/3 mm.
Conclusions: The developed source model showed good agreements between measured and cal-
culated dose distributions. The model is easily applicable to any other linear accelerator using FFF
beams as the required data include only the measured PDD, dose profiles, and output factors for
various field sizes, which are easily acquired during conventional beam commissioning
process. |
 2011_조웅_Med.Phys.PDF (1.3M) [970] DATE : 2011-10-10 18:33:31 |
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