Gold nanoparticles are promising radiosensitizers for proton radiotherapy. However, the physical mechanisms of gold nanoparticles radiosensitization remain unclear. In the present study, the Geant4 toolkit was used to estimate by the Monte-Carlo simulation the changes (1) in the contribution of primary and secondary particles to the absorbed dose, (2) in the dose-averaged linear energy transfer, and (3) in the relative biological effectiveness of a 150 MeV proton beam caused by the addition of 50 mg/mL of gold nanoparticles to the irradiated water phantom. In the presence of gold nanoparticles no significant changes in the absorbed dose and the Bragg peak position were found, at the same time a redistribution of the contribution of secondary particles to the absorbed dose was recorded. An increase in the contributions from protons (~16%), recoil nuclei (~58%), α-particles (~400%), deuterons (~900%), tritons (~3000%), and photons (~7000%) was observed ~10 mm beyond the Bragg peak. The contribution of the secondary electrons decreased by ~35%. This redistribution led to ~5-fold increase in the dose-averaged linear energy transfer at the distal edge of the Bragg curve; this, in turn, may cause the ~1.4−2.2-fold increase in the relative biological effectiveness within this region. Thus, it is critically important to take into account the presence of gold nanoparticles when dosimetric planning proton radiotherapy in order to avoid unwanted damage to the normal tissues around the tumor.

中文翻译：

---

金纳米粒子存在下临床质子束线性能量转移的变化

金纳米粒子是用于质子放射治疗的有前途的放射增敏剂。然而，金纳米粒子放射增敏的物理机制仍不清楚。在本研究中，Geant4 工具包用于通过 Monte-Carlo 模拟估计初级和次级粒子对吸收剂量的贡献的变化（1），（2）剂量平均线性能量转移的变化，以及（ 3) 在 150 MeV 质子束的相对生物有效性中，由于向受照射的水体模中添加了 50 mg/mL 的金纳米粒子而引起的。在金纳米粒子的存在下，没有发现吸收剂量和布拉格峰位置的显着变化，同时记录了二次粒子对吸收剂量的贡献的重新分布。质子的贡献增加（~16%），在布拉格峰外约 10 毫米处观察到反冲核 (~58%)、α 粒子 (~400%)、氘核 (~900%)、氚核 (~3000%) 和光子 (~7000%)。二次电子的贡献减少了~35%。这种重新分布导致布拉格曲线远端边缘的剂量平均线性能量转移增加了约 5 倍；反过来，这可能导致该区域内的相对生物有效性增加约 1.4-2.2 倍。因此，在剂量学计划质子放疗时考虑金纳米粒子的存在至关重要，以避免对肿瘤周围的正常组织造成不必要的损害。这种重新分布导致布拉格曲线远端边缘的剂量平均线性能量转移增加了约 5 倍；反过来，这可能导致该区域内的相对生物有效性增加约 1.4-2.2 倍。因此，在剂量学计划质子放疗时考虑金纳米粒子的存在至关重要，以避免对肿瘤周围的正常组织造成不必要的损害。这种重新分布导致布拉格曲线远端边缘的剂量平均线性能量转移增加了约 5 倍；反过来，这可能导致该区域内的相对生物有效性增加约 1.4-2.2 倍。因此，在剂量学计划质子放疗时考虑金纳米粒子的存在至关重要，以避免对肿瘤周围的正常组织造成不必要的损害。