Improving delivery efficiency using spots and energy layers reduction algorithms based on a large momentum acceptance beamline.
Improving delivery efficiency using spots and energy layers reduction algorithms based on a large momentum acceptance beamline.
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DOI：
10.1002/mp.16420
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发表时间：
2023-04
期刊：
影响因子：
3.8
通讯作者：
Wei Wang;Xu Liu;Zhiyong Yang;Y. Liao;Peilun Li;Runxiao Zhao;B. Qin
中科院分区：
文献类型：
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作者：
Wei Wang;Xu Liu;Zhiyong Yang;Y. Liao;Peilun Li;Runxiao Zhao;B. Qin
背景：调强质子治疗（IMPT）是一种众所周知的质子治疗方法。除了提高计划质量外，缩短交付时间也是IMPT计划的关键。它可以增强患者的舒适度，降低治疗成本，提高交付效率。从治疗疗效来看，它有助于减轻分数内运动，提高放疗的准确性，特别是对于移动的肿瘤。然而，在计划质量和交付时间之间存在一个权衡问题。我们考虑了大动量接受（LMA）光束线的潜力，并应用了斑点和能量层减少方法来缩短交货时间。方法每个场的传递时间包括能量层切换时间、光斑移动时间和剂量传递时间。与传统光束线相比，LMA光束线提供的更大动量扩展和更高强度的光束有助于缩短总传输时间。在目标函数中除了剂量保真度项外，还增加了L1和对数项，以增加低权重点和能量层的稀疏度。然后，将低权重的点和层迭代地排除在简化方案中，从而减少了能量层切换时间和点移动时间。我们使用标准、简化和lma简化的计划来验证所提出的方法，并在前列腺和鼻咽病例中进行了测试。然后，我们比较和评估了计划质量、治疗时间和计划对交付不确定性的鲁棒性。结果与标准方案相比，减少lma方案前列腺组平均减少13 400个（95.6%），鼻咽组平均减少48 300个（80.7%），前列腺组平均减少49个（61.3%），鼻咽组平均减少97个（50.5%）。前列腺病例和鼻咽部病例的交付时间分别由34.5 s和163.8 s缩短至53.6 s。与标准方案相比，lma -约简方案对现场监测单元误差具有相当的鲁棒性，但lma -约简方案对现场位置不确定性更为敏感。结论采用LMA光束线、光斑和能量层减少策略可显著提高递送效率。该方法有望提高运动缓解策略治疗移动肿瘤的效率。
BACKGROUND Intensity-modulated proton therapy (IMPT) is a well-known delivery method of proton therapy. Besides higher plan quality, reducing the delivery time is also essential to IMPT plans. It can enhance patient comfort, reduce treatment costs, and improve delivery efficiency. From the perspective of treatment efficacy, it contributes to mitigating the intra-fractional motions and improving the accuracy of radiotherapy, especially for moving tumors. PURPOSE However, there is a tradeoff problem between the plan quality and delivery time. We consider the potential of a large momentum acceptance (LMA) beamline and apply the spots and energy layers reduction method to reduce the delivery time. METHODS The delivery time for each field consists of the energy layer switching time, spot traveling time, and dose delivery time. The larger momentum spread and higher intensity beam offered by the LMA beamline contribute to reducing the total delivery time compared to the conventional beamline. In addition to the dose fidelity term, an L1 and logarithm items were added to the objective function to increase the sparsity of the low-weighted spots and energy layers. After that, the low-weighted spots and layers were iteratively excluded in the reduced plan, which reduced the energy layer switching time and spot traveling time. We used the standard, reduced, and LMA-reduced plans to validate the proposed method and tested it on prostate and nasopharyngeal cases. Then, we compared and evaluated the plan quality, treatment time, and plan robustness against delivery uncertainty. RESULTS Compared with the standard plans, the number of spots in the LMA-reduced plans was on average reduced by 13 400 (95.6%) for prostate cases and by 48 300 (80.7%) for nasopharyngeal cases and the number of energy layers was on average reduced by 49 (61.3%) for prostate cases and by 97 (50.5%) for nasopharyngeal cases. And, the delivery time of the LMA-reduced plans was shortened from 34.5 to 8.6 s for prostate cases and from 163.8 to 53.6 s for nasopharyngeal cases. The LMA-reduced plans had comparable robustness to the spot monitor unit (MU) error compared with the standard plans, but the LMA-reduced plans became more sensitive to spot position uncertainty. CONCLUSION The delivery efficiency can be significantly improved using the LMA beamline and spots and energy layers reduction strategies. The method is promising to improve the efficiency of motion mitigation strategies for treating moving tumors.