Intensity modulation methods for proton radiotherapy
Intensity modulation methods for proton radiotherapy
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DOI：
10.1088/0031-9155/44/1/014
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发表时间：
1999-01-01
影响因子：
3.5
通讯作者：
Lomax, A
中科院分区：
文献类型：
--
作者：
Lomax, A
质子或重离子的特征布拉格峰在三维空间中提供了很好的剂量定位。通过其提供横向和远端形状均匀场的能力，质子已被证明是提供高度适形放射治疗的精确和实用方法。然而，与光子的强度调制类似，质子可以通过应用许多单独的非均匀场来构建剂量分布，但是在布拉格峰中的剂量局部化提供了在二维或三维空间内调制强度的可能性。我们描述了四种不同的质子强度调制方法，并描述了如何在现有的质子规划系统中实现这些方法。作为对这些方法有效性的初步评价，每一种方法都应用于一个使用各种领域组合的示例案例。结果剂量分布的剂量-体积直方图分析表明，当使用大量场时，所有技术都表现出良好的靶均匀性和邻近关键结构的节约，四种技术之间的差异很小。然而，随着场数的减少，只有单个布拉格峰的全三维调制才能保持目标覆盖和正常组织的保留。我们得出的结论是，在具有挑战性的情况下，三维方法在构建适形剂量方面提供了最大的灵活性，但是当有大量光束端口可用时，从深度的额外强度调制中获得的优势很小。
The characteristic Bragg peak of protons or heavy ions provides a good localization of dose in three dimensions. Through their ability to deliver laterally and distally shaped homogenous fields, protons have been shown to be a precise and practical method for delivering highly conformal radiotherapy. However, in an analogous manner to intensity modulation for photons, protons can be used to construct dose distributions through the application of many individually inhomogeneous fields, but with the localization of dose in the Bragg peak providing the possibility of modulating intensity within each held in two or three dimensions. We describe four different methods of intensity modulation for protons and describe how these have been implemented in an existing proton planning system. As a preliminary evaluation of the efficacy of these methods, each has been applied to an example case using a variety of field combinations. Dose-volume histogram analysis of the resulting dose distributions shows that when large numbers of fields are used, all techniques exhibit both good target homogeneity and sparing of neighbouring critical structures, with little difference between the four techniques being discerned. As the number of fields is decreased, however, only a full 3D modulation of individual Bragg peaks can preserve both target coverage and sparing of normal tissues. We conclude that the 3D method provides the greatest flexibility far constructing conformal doses in challenging situations, but that when large numbers of beam ports are available, little advantage may be gained from the additional modulation of intensity in depth.