Scatter fractions from linear accelerators with x-ray energies from 6 to 24 MV
Scatter fractions from linear accelerators with x-ray energies from 6 to 24 MV
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DOI：
10.1118/1.598670
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发表时间：
1999-08-01
期刊：
影响因子：
3.8
通讯作者：
Shobe, J
中科院分区：
文献类型：
--
作者：
Taylor, PL;Rodgers, JE;Shobe, J
直线加速器屏蔽要求的计算必须考虑从患者散射到初级射束以外区域的辐射量。目前，最常用的数据来自NCRP 49，其仅包括最高6 MV的X射线能量和30度至135度的角度的数据。在这项工作中，我们已经确定了Monte Carlo模拟的散射分数的剂量为广泛的能量和角度的临床意义，包括6，10，18，和24 MV和散射角从10度到150度。对400 cm（2）圆形射野大小撞击球形体模进行了计算。在离体模1 m处确定剂量的散射分数。10度到30度的角度对于散射主要在前向方向上的较高能量是有意义的。散射分数的误差可能导致在与主势垒的结附近的次级屏蔽太少。Sandia国家实验室和NIST开发的Monte Carlo代码ITS（3.0版）用于模拟从患者到屏障的散射。重要的是计算的散射剂量随屏障内测量深度的变化，表明可能难以获得准确的值。给出了散射X射线谱的平均能量。(C)1999年美国医学物理学家协会。[S0094-2405（99）01008-1]。
Computation of shielding requirements for a linear accelerator must take into account the amount of radiation scattered from the patient to areas outside the primary beam. Currently, the most frequently used data are from NCRP 49 that only includes data for x-ray energies up to 6 MV and angles from 30 degrees to 135 degrees. In this work we have determined by Monte Carlo simulation the scattered fractions of dose for a wide range of energies and angles of clinical significance including 6, 10, 18, and 24 MV and scattering angles from 10 degrees to 150 degrees. Calculations were made for a 400 cm(2) circular field size impinging onto a spherical phantom. Scattered fractions of dose were determined at I m from the phantom. Angles from 10 degrees to 30 degrees are of concern for higher energies where the scatter is primarily in the forward direction. An error in scatter fraction may result in too little secondary shielding near the junction with the primary barrier. The Monte Carlo code ITS (Version 3.0) developed at Sandia National Laboratory and NIST was used to simulate scatter from the patient to the barrier. Of significance was the variation of calculated scattered dose with depth of measurement within the barrier indicating that accurate values may be difficult to obtain. Mean energies of scatter x-ray spectra are presented. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)01008-1].