Ma Chaoqiong, Zhou Jun, Chang Chih-Wei, Wang Yinan, Patel Pretesh R, Yu David S, Tian Sibo, Yang Xiaofeng
ArXiv. 2023 Oct 3:arXiv:2306.12304v2.
This study explored the feasibility of a streamlined pin-shaped ridge filter (pin-RF) design for single-energy proton FLASH planning.
An inverse planning framework integrated within a TPS was established for FLASH planning. The framework involves generating a IMPT plan based on downstream energy modulation strategy (IMPT-DS), followed by a nested spot reduction process to iteratively reduce the total number of pencil beam directions (PBDs) and energy layers along each PBD for the IMPT-DS plan. The IMPT-DS plan is then translated into the pin-RFs for a single-energy IMPT plan (IMPT-RF). The framework was validated on three lung cases, quantifying the FLASH dose of the IMPT-RF plan using the FLASH effectiveness model and comparing it with the reference dose of a conventional IMPT plan to assess the clinical benefit of the FLASH planning technique.
The IMPT-RF plans closely matched the corresponding IMPT-DS plans in high dose conformity, with minimal changes in V7Gy and V7.4Gy for the lung (< 5%) and small increases in Dmax for other OARs (< 3.2 Gy). Comparing the FLASH doses to the doses of corresponding IMPT-RF plans, drastic reductions of up to ~33% were observed in Dmax for OARs in the high-to-moderate-dose regions with negligible changes in Dmax for OARs in low-dose regions. Positive clinical benefits were observed with notable reductions of 18.4-33.0% in Dmax for OARs in the high-dose regions. However, in the moderate-to-low-dose regions, only marginal positive or even negative clinical benefit for OARs were observed, such as increased lung V7Gy and V7.4Gy (16.4-38.9%).
A streamlined pin-RF design for single-energy proton FLASH planning was validated, revealing positive clinical benefits for OARs in the high dose regions. The coarsened design of the pin-RF demonstrates potential cost efficiency and efficient production.
本研究探讨了用于单能质子FLASH放疗计划的简化针状脊形滤波器（pin-RF）设计的可行性。
建立了一个集成在治疗计划系统（TPS）中的逆向计划框架用于FLASH放疗计划。该框架包括基于下游能量调制策略生成调强质子治疗（IMPT）计划（IMPT-DS），随后进行嵌套式射野缩减过程，以迭代减少IMPT-DS计划中每个笔形束方向（PBD）的铅笔束方向总数和沿每个PBD的能量层数。然后将IMPT-DS计划转换为用于单能IMPT计划（IMPT-RF）的pin-RF。该框架在三个肺部病例上进行了验证，使用FLASH有效性模型量化IMPT-RF计划的FLASH剂量，并将其与传统IMPT计划的参考剂量进行比较，以评估FLASH放疗技术的临床益处。
IMPT-RF计划在高剂量适形性方面与相应的IMPT-DS计划紧密匹配，肺部的V7Gy和V7.4Gy变化极小（<5%），其他危及器官（OAR）的Dmax略有增加（<3.2 Gy）。将FLASH剂量与相应IMPT-RF计划的剂量进行比较，在中高剂量区域的OAR中观察到Dmax大幅降低，降幅高达约33%，而低剂量区域的OAR的Dmax变化可忽略不计。在高剂量区域的OAR中观察到了积极的临床益处，Dmax显著降低了18.4% - 33.0%。然而，在中低剂量区域，仅观察到OAR的轻微积极甚至消极的临床益处，例如肺部的V7Gy和V7.4Gy增加（16.4% - 38.9%）。
用于单能质子FLASH放疗计划的简化pin-RF设计得到了验证，显示出在高剂量区域对OAR有积极的临床益处。pin-RF的粗化设计显示出潜在的成本效益和高效生产能力。
