Ma Chaoqiong, Yang Xiaofeng, Wang Yinan, Yu David, Patel Pretesh, Zhou Jun
ArXiv. 2024 Jun 4:arXiv:2406.02718v1.
We previously developed a FLASH planning framework for streamlined pin-ridge-filter (pin-RF) design, demonstrating its feasibility for single-energy proton FLASH planning. In this study, we refined the pin-RF design for easy assembly using reusable modules, focusing on its application in liver SABR. This framework generates an intermediate IMPT plan and translates it into step widths and thicknesses of pin-RFs for a single-energy FLASH plan. Parameters like energy spacing, monitor unit limit, and spot quantity were adjusted during IMPT planning, resulting in pin-RFs assembled using predefined modules with widths from 1 to 6 mm, each with a WET of 5 mm. This approach was validated on three liver SABR cases. FLASH doses, quantified using the FLASH effectiveness model at 1 to 5 Gy thresholds, were compared to conventional IMPT (IMPT-CONV) doses to assess clinical benefits. The highest demand for 6 mm width modules, moderate for 2-4 mm, and minimal for 1- and 5-mm modules were shown across all cases. At lower dose thresholds, the two-beam case showed significant dose reductions (>23%), while the other two three-beam cases showed moderate reductions (up to 14.7%), indicating the need for higher fractional beam doses for an enhanced FLASH effect. Positive clinical benefits were seen only in the two-beam case at the 5 Gy threshold. At the 1 Gy threshold, the FLASH plan of the two-beam case outperformed its IMPT-CONV plan, reducing dose indicators by up to 28.3%. However, the three-beam cases showed negative clinical benefits at the 1 Gy threshold, with some dose indicators increasing by up to 16% due to lower fractional beam doses and closer beam arrangements. This study evaluated the feasibility of modularizing streamlined pin-RFs in single-energy proton FLASH planning for liver SABR, offering guidance on optimal module composition and strategies to enhance FLASH planning.
我们之前开发了一种用于简化针状脊形滤波器（pin-RF）设计的FLASH规划框架，证明了其在单能质子FLASH规划中的可行性。在本研究中，我们对pin-RF设计进行了改进，以便使用可重复使用的模块进行轻松组装，重点关注其在肝脏SABR中的应用。该框架生成一个中间的调强质子治疗（IMPT）计划，并将其转换为单能FLASH计划的pin-RF的步长和厚度。在IMPT规划过程中调整了能量间距、监测单位限制和光斑数量等参数，从而使用宽度为1至6毫米、每个的水等效厚度（WET）为5毫米的预定义模块组装pin-RF。该方法在三个肝脏SABR病例上得到了验证。使用FLASH有效性模型在1至5 Gy阈值下量化的FLASH剂量与传统IMPT（IMPT-CONV）剂量进行比较，以评估临床益处。在所有病例中，对6毫米宽模块的需求最高，对2至4毫米宽模块的需求适中，对1毫米和5毫米宽模块的需求最小。在较低剂量阈值下，双束病例显示出显著的剂量降低（>23%），而其他两个三束病例显示出适度的降低（高达14.7%），这表明需要更高的分次束剂量来增强FLASH效应。仅在5 Gy阈值的双束病例中观察到了积极的临床益处。在1 Gy阈值下，双束病例的FLASH计划优于其IMPT-CONV计划，剂量指标降低了高达28.3%。然而，三束病例在1 Gy阈值下显示出负面的临床益处，由于较低的分次束剂量和更紧密的束排列，一些剂量指标增加了高达16%。本研究评估了在肝脏SABR的单能质子FLASH规划中对简化的pin-RF进行模块化的可行性，为优化模块组成和增强FLASH规划的策略提供了指导。
