质子弧疗法（PAT）是一种新兴的治疗模式，有望改善靶体积覆盖和降低靶周围器官的线性能量传递（LET）。我们的目标是研究在每个射束方向中修剪最高能量层是否能增加靶区的LET并减少组织和靶周围器官的LET，从而减少相对生物效应（RBE）加权剂量并保护健康组织。使用Eclipse治疗计划系统，为生发肿瘤、脑脊液瘤和横纹肌肉瘤患者制定了54 Gy（RBE）的处方剂量，使用常数RBE（RBE1.1）为1.1。对PAT计划进行了修剪，创建了几个带有不同修剪程度的PAT计划，同时保持肿瘤覆盖，称为PX-PAT计划，其中X表示修剪程度。所有计划在FLUKA Monte Carlo软件中进行重新计算，并评估了来自现象学Rørvik（ROR）模型和一个LET加权剂量（LWD）模型的LET、物理剂量和可变RBE加权剂量。对于生发细胞瘤情况，除了P6-PAT计划之外，所有计划都减少了相对于PAT计划的平均RBE加权剂量。在每个修剪迭代中，PTV内的LET逐渐增高，其中P6-PAT计划的平均LET比PAT计划高1.5 keV/μm，而P4-PAT和P5-PAT计划分别增加了0.4和0.7 keV/μm。与PAT计划相比，其他计划的LET增加幅度较小。同样，健康组织的LET值在每种修剪程度下也减少了。对于脑脊液瘤和横纹肌肉瘤情况，也获得了类似的结果。我们展示了一种PAT修剪技术，可以增加靶区体积的LET和RBE，并同时降低健康组织中的数值，而不影响靶区剂量覆盖。 版权所有 © 2023 Henjum, Tjelta, Fjæra, Pilskog, Stokkevåg, Lyngholm, Handeland和Ytre-Hauge。

Proton arc therapy (PAT) is an emerging treatment modality that holds promise to improve target volume coverage and reduce linear energy transfer (LET) in organs at risk. We aimed to investigate if pruning the highest energy layers in each beam direction could increase the LET in the target and reduce LET in tissue and organs at risk (OAR) surrounding the target volume, thus reducing the relative biological effectiveness (RBE)-weighted dose and sparing healthy tissue.PAT plans for a germinoma, an ependymoma and a rhabdomyosarcoma patient were created in the Eclipse treatment planning system with a prescribed dose of 54 Gy(RBE) using a constant RBE of 1.1 (RBE1.1). The PAT plans was pruned for high energy spots, creating several PAT plans with different amounts of pruning while maintaining tumor coverage, denoted PX-PAT plans, where X represents the amount of pruning. All plans were recalculated in the FLUKA Monte Carlo software, and the LET, physical dose, and variable RBE-weighted dose from the phenomenological Rørvik (ROR) model and an LET weighted dose (LWD) model were evaluated.For the germinoma case, all plans but the P6-PAT reduced the mean RBE-weighted dose to the surrounding healthy tissue compared to the PAT plan. The LET was increasingly higher within the PTV for each pruning iteration, where the mean LET from the P6-PAT plan was 1.5 keV/μm higher than for the PAT plan, while the P4- and P5-PAT plans provided an increase of 0.4 and 0.7 keV/μm, respectively. The other plans increased the LET by a smaller margin compared to the PAT plan. Likewise, the LET values to the healthy tissue were reduced for each degree of pruning. Similar results were found for the ependymoma and the rhabdomyosarcoma case. We demonstrated a PAT pruning technique that can increase both LET and RBE in the target volume and at the same time decreased values in healthy tissue, without affecting the target volume dose coverage.Copyright © 2023 Henjum, Tjelta, Fjæra, Pilskog, Stokkevåg, Lyngholm, Handeland and Ytre-Hauge.