He Pengbo, Li Qiang
Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China.
Key Laboratory of Heavy Ion Radiation Biology and Medicine, Chinese Academy of Sciences, Lanzhou, China.
Front Oncol. 2022 Feb 11;12:806742. doi: 10.3389/fonc.2022.806742. eCollection 2022.
The characteristic of pulsed beam delivery for synchrotron-based carbon-ion radiotherapy has led to the emergence of many scanning scenarios in order to improve the treatment efficiency and accuracy of moving target volume. Here, we aim to evaluate a novel breathing guidance motion mitigation performance under different synchrotron flattop operation modes in carbon-ion radiotherapy.
With the use of twelve 4DCT datasets of lung cancer patients who had been treated with respiratory-gated carbon-ion pencil beam therapy, range-adapted internal target volume (raITV) plans were optimized. Under the fixed flattop with single-energy and extended flattop with multi-energy synchrotron operation modes, the 4D treatments with breathing guidance and free breathing-based gated phase-controlled rescanning (PCR) beam delivery were simulated. Dose metrics (D95 and D5-D95 in clinical target volume (CTV)) and treatment time of the resulting 4D plans were compared.
The two synchrotron operation modes provided different scanning dynamics. For the free breathing-based PCR method delivered in the extended flattop operation mode, the averaged CTV-D95 values were 90.4% ± 3.7%, 95.4% ± 1.7%, 96.9% ± 1.5%, 97.2% ± 1.5%, and 97.3% ± 1.5% for the 1-scanning, 2-PCR, 4-PCR, 6-PCR, and 8-PCR, respectively. For the breathing guidance-based PCR method delivered in the extended flattop mode, these values were 89.1% ± 4.0%, 97.0% ± 1.4%, 98.2% ± 0.7%, 98.6% ± 0.7%, and 98.9% ± 0.7%, respectively. However, CTV-D95 significantly increased to 98.5% ± 1.0% even with just 1-scanning breathing guidance-based fixed flattop operation mode (p < 0.01). Moreover, there was no significant difference in treatment time among the three technical combinations (p > 0.15).
The combination of the breathing guidance and PCR methods should be an alternative way for motion mitigation for the fixed flattop synchrotron operation mode. The target dose coverage and homogeneity could be further improved by the combination of the breathing guidance and PCR methods than the traditional PCR-only technology for the extended flattop synchrotron operation mode.
基于同步加速器的碳离子放射治疗中脉冲束输送的特性导致了许多扫描方案的出现，以提高移动靶区的治疗效率和准确性。在此，我们旨在评估碳离子放射治疗中不同同步加速器平顶运行模式下一种新型呼吸引导运动缓解性能。
利用12例接受呼吸门控碳离子笔形束治疗的肺癌患者的4DCT数据集，优化了范围适应内靶区（raITV）计划。在单能固定平顶和多能扩展平顶同步加速器运行模式下，模拟了基于呼吸引导和基于自由呼吸的门控相位控制重扫描（PCR）束输送的4D治疗。比较了所得4D计划的剂量指标（临床靶区（CTV）中的D95和D5 - D95）和治疗时间。
两种同步加速器运行模式提供了不同的扫描动态。对于在扩展平顶运行模式下基于自由呼吸的PCR方法，1次扫描、2次PCR、4次PCR、6次PCR和8次PCR时的平均CTV - D95值分别为90.4%±3.7%、95.4%±1.7%、96.9%±1.5%、97.2%±1.5%和97.3%±1.5%。对于在扩展平顶模式下基于呼吸引导的PCR方法，这些值分别为89.1%±4.0%、97.0%±1.4%、98.2%±0.7%、98.6%±0.7%和98.9%±0.7%。然而，即使在仅基于1次扫描呼吸引导的固定平顶运行模式下，CTV - D95也显著增加至98.5%±1.0%（p < 0.01）。此外，三种技术组合之间的治疗时间无显著差异（p > 0.15）。
呼吸引导和PCR方法的组合应为固定平顶同步加速器运行模式下的运动缓解提供一种替代方法。对于扩展平顶同步加速器运行模式，与传统的仅PCR技术相比，呼吸引导和PCR方法的组合可进一步提高靶区剂量覆盖和均匀性。
