Yamada Masanori, Inakoshi Hideki, Hayakawa Takahide, Inoue Tomio, Kasahara Toshifumi, Igarashi Satoshi
Department of Medical Radiation Technology, School of Health Sciences, Niigata University.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2006 Dec 20;62(12):1675-81. doi: 10.6009/jjrt.62.1675.
To more easily estimate accurate values of collimator scatter facor, S(c), we suggest a two-component saturation model that accounts for scatter from the primary collimator and flattening filter and from the collimator jaws. This model, which assumes an exponential distribution of scatter intensity, was tested by in-air measurements using a mini-phantom for 4 MV and 10 MV X-rays of a Clinac 2100 C/D linear accelerator. The results showed a good fit of this model to our measured data (R(2)>0.9993). When the measured value was divided into the primary collimator/flattening filter component and the collimator jaw component, as expected, the former component showed a rapid and full saturation curve with increased field size, while the latter showed an almost linearly increasing curve. Therefore, we think that this saturation model is useful for the estimation of S(c) and is applicable to monitor unit calculation for an asymmetric field.
为了更轻松地估算准直器散射因子S(c)的准确值，我们提出了一种双组分饱和模型，该模型考虑了来自初级准直器、均整器以及准直器钳口的散射。此模型假设散射强度呈指数分布，我们使用迷你体模对Clinac 2100 C/D直线加速器的4 MV和10 MV X射线进行了空气测量，对该模型进行了测试。结果表明该模型与我们的测量数据拟合良好（R(2)>0.9993）。当将测量值分为初级准直器/均整器组分和准直器钳口组分时，正如预期的那样，前一组分随着射野尺寸的增加呈现出快速且完全饱和的曲线，而后一组分则呈现出几乎线性增加的曲线。因此，我们认为这种饱和模型对于估算S(c)是有用的，并且适用于非对称射野的监测单位计算。
