New York Proton Center, New York, NY 10035, USA.
New York Proton Center, New York, NY 10035, USA.
Radiother Oncol. 2022 Oct;175:238-247. doi: 10.1016/j.radonc.2022.08.005. Epub 2022 Aug 10.
To investigate the dosimetric characteristics between an advanced proton pencil beam scanning (PBS) Bragg peak FLASH technique and conventional PBS planning technique in lung tumors. To evaluate the "FLASHness" of single-field in a multiple-field delivery scheme for a hypofractionation regimen and move a step forward to clinical application.
Single-energy PBS Bragg peak FLASH treatment plans were optimized based on a novel Bragg peak tracking technique to enable Bragg peaks to stop at the distal edge of the target. Inverse treatment planning using multiple-field optimization (MFO) can achieve sufficient FLASH dose rate and intensity-modulated proton therapy (IMPT)-equivalent dosimetric quality. The dose rate of organs-at-risk (OARs) and the target were calculated under FLASH machine parameters. A group of 10 consecutive lung SBRT patients was optimized to 34 Gy/fraction using a standard treatment of PBS technique with multiple energy layers as references to the Bragg peak plans. The dosimetric quality was compared between Bragg peak FLASH and conventional plans based on RTOG0915 dose metrics. FLASH dose rate ratios (V) were calculated as a metric of the FLASH-sparing effect.
For higher dose thresholds, the Bragg peak plans achieved greater V FLASH coverage for all major OARs. The V40Gy/s was close to 100% for all OARs when the dose thresholds were > 5 Gy for full plan and single beam evaluations. The less "FLASHness" region was associated with a low dose distribution, mainly occurring in the PBS field penumbra region. The conventional IMPT treatment plans yielded slightly superior target dose uniformity with a D(%) of 108.02% versus that of Bragg peak 300 MU plans of 111.81% (p < 0.01) and that of Bragg peak 1200 MU plans of 115.95% (p < 0.01). No significant difference in dose metrics was found between Bragg peak and IMPT treatment plans for the spinal cord, esophagus, heart, or lung-GTV (all p > 0.05).
Hypofractionated lung Bragg peak plans can maintain comparable plan quality to conventional PBS while achieving sufficient FLASH dose rate coverage for major OARs for each field under the multiple-field delivery scheme. The novel Bragg peak FLASH technique has the potential to enhance lung cancer planning treatment outcomes compared to standard PBS treatment techniques.
研究先进的质子笔束扫描（PBS）布拉格峰 FLASH 技术与传统 PBS 计划技术在肺部肿瘤中的剂量学特征。评估多野治疗方案中单野的“FLASH 特性”对于分割剂量方案，并朝着临床应用迈进。
基于新的布拉格峰跟踪技术，优化单能 PBS 布拉格峰 FLASH 治疗计划，使布拉格峰在靶区的远端停止。使用多野优化（MFO）的逆治疗计划可以实现足够的 FLASH 剂量率和调强质子治疗（IMPT）等效的剂量学质量。在 FLASH 机器参数下计算危及器官（OARs）和靶区的剂量率。将一组 10 例连续的肺部 SBRT 患者优化为 34 Gy/分次，使用 PBS 技术的标准治疗，以多个能量层作为布拉格峰计划的参考。基于 RTOG0915 剂量学指标，比较布拉格峰 FLASH 和传统计划的剂量学质量。FLASH 剂量率比（V）作为 FLASH 节省效果的指标进行计算。
对于较高的剂量阈值，布拉格峰计划为所有主要 OARs 实现了更大的 VFLASH 覆盖率。当全计划和单束评估的剂量阈值>5 Gy 时，V40Gy/s 接近 100%，所有 OARs 均如此。较少的“FLASH 特性”区域与低剂量分布相关，主要发生在 PBS 野半影区。常规的 IMPT 治疗计划在 108.02%的靶区剂量均匀性方面略有优势，而布拉格峰 300 MU 计划为 111.81%（p<0.01），布拉格峰 1200 MU 计划为 115.95%（p<0.01）。脊髓、食管、心脏或肺部-GTV 的剂量学指标在布拉格峰和 IMPT 治疗计划之间无显著差异（均 p>0.05）。
对于多野治疗方案中的每个野，Hypofractionated 肺部布拉格峰计划可以在维持与传统 PBS 相当的计划质量的同时，为主要 OARs 实现足够的 FLASH 剂量率覆盖。与标准 PBS 治疗技术相比，新的布拉格峰 FLASH 技术具有提高肺癌计划治疗效果的潜力。
