Experimental characterization of two-dimensional pencil beam scanning proton spot profiles
Experimental characterization of two-dimensional pencil beam scanning proton spot profiles
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DOI：
10.1088/0031-9155/58/17/6193
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发表时间：
2013-09-07
影响因子：
3.5
通讯作者：
McDonough, James E.
中科院分区：
文献类型：
--
作者：
Lin, Liyong;Ainsley, Christopher G.;McDonough, James E.
笔形射束扫描治疗计划的剂量计算依赖于质子斑点轮廓的准确性;不仅是主要成分，而且是宽尾成分。将四个膜放置在空气中的几个位置和Solidwater（R）中的多个深度，用于六种选定的能量。用于主要组件的薄膜暴露于50-200 MU以避免饱和;用于尾部组件的薄膜暴露于800、8000和80 000 MU。通过应用配对/放大方法并合并这些数据，可以生成低至中心点剂量的10（-4）的剂量核。从这些内核可以计算剂量每MU为不同的字段大小和形状。测量同意在1%的剂量内核为基础的计算输出与字段大小比较。不对称的彗星形轮廓尾巴在表面深度和低能量下有更大的影响：在40 mm x 200 mm的矩形场的表面上，两个方向之间的输出差异在100 MeV的等中心处约为2%。从0到40 mm半径的这些剂量核的积分表明，布拉格峰室中的电荷赤字变化
Dose calculations of pencil beam scanning treatment plans rely on the accuracy of proton spot profiles; not only the primary component but also the broad tail components. Four films are placed at several locations in air and multiple depths in Solidwater (R) for six selected energies. The films used for the primary components are exposed to 50-200 MU to avoid saturation; the films used for the tail components are exposed to 800, 8000 and 80 000 MU. By applying a pair/magnification method and merging these data, dose kernels down to 10(-4) of the central spot dose can be generated. From these kernels one can calculate the dose-per-MU for different field sizes and shapes. Measurements agree within 1% of dose-kernel-based calculations for output versus field size comparisons. Asymmetric, comet-shaped profile tails have a bigger impact at superficial depths and low energies: the output difference between two orientations at the surface of a rectangular field of 40 mm x 200 mm is about 2% at the isocentre at 100 MeV. Integration of these dose kernels from 0 to 40 mm radius shows that the charge deficit in the Bragg peak chamber varies