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首页> 外文期刊>Medical Physics >Estimation of the dose at the maze entrance for x-rays from radiotherapy linear accelerators.
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Estimation of the dose at the maze entrance for x-rays from radiotherapy linear accelerators.

机译：迷宫入口处放射治疗线性加速器的X射线剂量估算。

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摘要

Recent measurements have shown that the NCRP formula to estimate the x radiation dose at the maze entrance of high energy radiotherapy rooms underestimates the dose by an order of magnitude. In the present work the Monte Carlo Code MCNP was used to model a radiotherapy room and investigate the NCRP formula. The dose of the scattered photons was calculated for 6-MV and 10-MV x-rays for the following situations: primary beam in vacuum, primary beam with air in the room, collimated primary beam (by the jaws) with air in the room and primary beam collimated with air in the room, and phantom at 100-cm SSD. It was found that for 6-MV x-rays the dose, when these materials were present in the beam path, was 1.2, 1.6, 5.3, and 13.1 x 10(-22) Gy photon(-1), respectively. Therefore the presence of all these materials together increased the dose by a factor of 11. The dose due to leakage was calculated separately to be 9.1 x 10(-22) Gy photon(-1). This adds another factor of 8. The 10-MV results were similar to those at 6 MV. There was good agreement between MCNP calculations and the published measurements. The spectrum and average energy of scattered photons at different locations in the radiotherapy room and the maze were also calculated by MCNP.
机译：最近的测量结果表明，估算高能放射治疗室迷宫入口处x辐射剂量的NCRP公式低估了剂量一个数量级。在当前的工作中，使用蒙特卡罗代码MCNP对放射治疗室进行建模并研究NCRP公式。在以下情况下，针对6-MV和10-MV X射线计算了散射光子的剂量：真空中的主光束，房间中有空气的主光束，房间中有空气的准直主光束（通过钳口）主光束与室内的空气准直，并在100厘米固态硬盘上幻像。已经发现，对于6-MV X射线，当这些材料存在于光路中时，剂量分别为1.2、1.6、5.3和13.1 x 10（-22）Gy光子（-1）。因此，所有这些材料的存在一起使剂量增加了11倍。由于泄漏导致的剂量分别计算为9.1 x 10（-22）Gy光子（-1）。这又增加了8倍。10-MV结果类似于6 MV时的结果。 MCNP计算与已发布的度量之间存在良好的一致性。 MCNP还计算了放疗室和迷宫中不同位置的散射光子的光谱和平均能量。

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