Dose- and LET-painting with particle therapy
Dose- and LET-painting with particle therapy
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DOI：
10.3109/0284186x.2010.510640
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发表时间：
2010-10-01
期刊：
影响因子：
3.1
通讯作者：
Petersen, Jorgen B.
中科院分区：
文献类型：
--
作者：
Bassler, Niels;Jaekel, Oliver;Petersen, Jorgen B.
肿瘤缺氧是在放射治疗中获得肿瘤控制的限制因素之一。重带电粒子束（如碳离子）的高LET区域位于布拉格峰的远端部分。调制或扩展布拉格峰（SOBP）是各种能量下的若干布拉格峰的加权函数，然而这导致靶体积中的剂量平均LET的稀释。在这里，我们研究了通过专用治疗计划优化重新分配LET的可能性，以最大限度地提高靶体积中的LET。这可能是一种潜在的克服缺氧沿着剂量递增或剂量涂抹的策略。高LET区域可以以非常不同的方式成形，同时保持吸收剂量或生物有效剂量的分布。仅涉及碳离子束的治疗计划显示出非常不同的LET分布，这取决于场的布置方式。或者，LET提升可以应用于多模式治疗计划中，例如将碳离子与质子和/或光子组合。对于这样的混合辐射模态，可以在目标体积内的几乎任意位置处实现显著的“LET提升”。缺氧，LET和氧增强比（OER）之间的关系的一般理解，我们得出结论，一个额外的治疗优势，可以通过限制高LET部分的辐射在肿瘤的缺氧区室，并施加低LET辐射的常氧组织。我们还预计，通过有意地从高LET区域保留正常组织，可以实现额外的优势。因此，基于同时剂量和LET优化的治疗计划有可能实现更高的肿瘤控制和/或降低正常组织控制概率（NTCP）。
Tumour hypoxia is one of the limiting factors in obtaining tumour control in radiotherapy. The high-LET region of a beam of heavy charged particles such as carbon ions is located in the distal part of the Bragg peak. A modulated or spread out Bragg peak (SOBP) is a weighted function of several Bragg peaks at various energies, which however results in a dilution of the dose-average LET in the target volume. Here, we investigate the possibility to redistribute the LET by dedicated treatment plan optimisation, in order to maximise LET in the target volume. This may be a strategy to potentially overcome hypoxia along with dose escalation or dose painting. The high-LET region can be shaped in very different ways, while maintaining the distribution of the absorbed dose or biological effective dose. Treatment plans involving only carbon ion beams, show very different LET distributions depending on how the fields are arranged. Alternatively, a LET boost can be applied in multi-modal treatment planning, such as combining carbon ions with protons and/or photons. For such mixed radiation modalities, significant "LET boosts" can be achieved at nearly arbitrary positions within the target volume. Following the general understanding of the relationship between hypoxia, LET and the oxygen enhancement ratio (OER), we conclude, that an additional therapeutic advantage can be achieved by confining the high-LET part of the radiation in hypoxic compartments of the tumour, and applying low-LET radiation to the normoxic tissue. We also anticipate that additional advantages may be achieved by deliberate sparing of normal tissue from high LET regions. Consequently, treatment planning based on simultaneous dose and LET optimisation has a potential to achieve higher tumour control and/or reduced normal tissue control probability (NTCP).