Calculation of k(Q(clin),Q(msr) ) (f(clin),f(msr) ) for several small detectors and for two linear accelerators using Monte Carlo simulations.
Calculation of k(Q(clin),Q(msr) ) (f(clin),f(msr) ) for several small detectors and for two linear accelerators using Monte Carlo simulations.
复制标题
使用蒙特卡罗模拟计算几个小型探测器和两个线性加速器的 k(Q(clin),Q(msr) ) (f(clin),f(msr) )。
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
N. Satariano
中科院分区：
文献类型：
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作者：
P. Francescon;S. Cora;N. Satariano
目的
本研究的范围是确定一套完整的校正因子的几个探测器在静态小光子场的两个直线加速器（直线加速器）和几个探测器。
方法
蒙特卡罗（MC）调试的测量进行了两个直线加速器，西门子Primus和Elekta协同。在已经确定了最适合于场特异性输出因子、轮廓和组织-体模比的测量的源参数之后，静态小场的经典射束质量校正因子k（Q（clin），Q（msr））（f（clin），f（msr））的广义版本，确定了几种类型的探测器通过使用EGS_腔室蒙特卡罗用户代码，可以准确地再现几何形状和材料组成的探测器。评估了许多参数（电子束源的能量和径向FWHM、场尺寸、加速器类型）对k（Q（clin），Q（msr））（f（clin），f（msr））值的影响。此外，MC分析的参数，影响的变化k（Q（clin），Q（msr））（f（clin），f（msr））作为字段尺寸的函数。详细分析了与现场特定输出因子的测量和与k（Q（clin），Q（msr））（f（clin），f（msr））的Monte Carlo计算有关的不确定度。
结果
模拟表明，对于所有分析的探测器，可以认为校正因子k（Q（clin），Q（msr））（f（clin），f（msr））在0.68 ± 0.01的范围内与质量光束因子Q无关。PTW 60012和EDGE二极管的k（Q（clin），Q（msr））（f（clin），f（msr））可以假设仅取决于场大小，场小至0.5 × 0.5 cm²。微狮和微室必须谨慎使用，因为它们对电子源的径向半高宽有轻微的依赖性，因此，仅依赖于场大小的校正因子可以分别用于≥ 0.75 × 0.75和≥ 1.0 × 1.0 cm²的场。不确定性分析给出了0.5 × 0.5 cm²场的不确定性估计，k（Q（clin），Q（msr））（f（clin），f（msr））因子约为0.7%（1σ），场输出因子Ω约为1.0%（1σ）（Q（clin），Q（msr））（f（clin），f（msr）），二极管、微室和microLion。
结论
建议使用具有适当k（Q（clin），Q（msr））（f（clin），f（msr））的立体定向二极管来确定小光子束的Ω（Q（clin），Q（msr））（f（clin），f（msr））。
PURPOSE
The scope of this study was to determine a complete set of correction factors for several detectors in static small photon fields for two linear accelerators (linacs) and for several detectors.
METHODS
Measurements for Monte Carlo (MC) commissioning were performed for two linacs, Siemens Primus and Elekta Synergy. After having determined the source parameters that best fit the measurements of field specific output factors, profiles, and tissue-phantom ratio, the generalized version of the classical beam quality correction factor for static small fields, k(Q(clin),Q(msr) ) (f(clin),f(msr) ), were determined for several types of detectors by using the egs_chamber Monte Carlo user code which can accurately reproduce the geometry and the material composition of the detector. The influence of many parameters (energy and radial FWHM of the electron beam source, field dimensions, type of accelerator) on the value of k(Q(clin),Q(msr) ) (f(clin),f(msr) ) was evaluated. Moreover, a MC analysis of the parameters that influence the change of k(Q(clin),Q(msr) ) (f(clin),f(msr) ) as a function of field dimension was performed. A detailed analysis of uncertainties related to the measurements of the field specific output factor and to the Monte Carlo calculation of k(Q(clin),Q(msr) ) (f(clin),f(msr) ) was done.
RESULTS
The simulations demonstrated that the correction factor k(Q(clin),Q(msr) ) (f(clin),f(msr) ) can be considered independent from the quality beam factor Q in the range 0.68 ± 0.01 for all the detectors analyzed. The k(Q(clin),Q(msr) ) (f(clin),f(msr) ) of PTW 60012 and EDGE diodes can be assumed dependent only on the field size, for fields down to 0.5 × 0.5 cm². The microLion, and the microchambers, instead, must be used with some caution because they exhibit a slight dependence on the radial FWHM of the electron source, and therefore, a correction factor only dependent on field size can be used for fields ≥ 0.75 × 0.75 and ≥ 1.0 × 1.0 cm², respectively. The analysis of uncertainties gave an estimate of uncertainty for the 0.5 × 0.5 cm² field of about 0.7% (1σ) for k(Q(clin),Q(msr) ) (f(clin),f(msr) ) factor and of about 1.0% (1σ) for the field output factor, Ω(Q(clin),Q(msr) ) (f(clin),f(msr) ), of diodes, microchambers, and microLion.
CONCLUSIONS
Stereotactic diodes with the appropriate k(Q(clin),Q(msr) ) (f(clin),f(msr) ) are recommended for determining Ω(Q(clin),Q(msr) ) (f(clin),f(msr) ) of small photon beams.