Evans Tucker, Cooley James, Wagner Miles, Yu Tianning, Zwart Townsend
Mevion Medical Systems, Littleton, MA, USA.
Int J Part Ther. 2021 Aug 19;8(4):68-75. doi: 10.14338/IJPT-20-00095. eCollection 2022 Spring.
The effects of FLASH-level dose rates delivered at the spread-out Bragg peak (SOBP) on normal tissue damage in mice were investigated.
Fifty nontumor-bearing mice received abdominal irradiation, 30 at FLASH dose rates (100 Gy/s) and 20 at conventional dose rates (0.1 Gy/s). Total dose values ranged from 10 to 19 Gy, delivered in a single spot by a synchrocyclotron proton therapy system. Centered on the abdomen, the collimated field delivered was an 11-mm diameter circle with a water-equivalent depth of 2.4 cm from entrance to distal 80% dose. A ridge filter was used to provide dose uniformity over the full 2.4-cm range. The spatial distribution was identical for both the FLASH and conventional deliveries.
Overall survival and individual mouse weights were tracked for 21 days after the exposure date, and LD50 values were compared for the FLASH and conventional dose rate groups. Mice exposed to FLASH dose rates had a higher LD50 value as compared with mice exposed to conventional dose rates, with a dose-dependent improvement in survivability of 10% to 20%. The FLASH cohort also showed greater or equal percent population survival for each day of the study.
These results are preliminary confirmation of the potential for the combination of the advantages of the Bragg peak with the normal tissue sparing benefits of FLASH treatments. This experiment also confirms that pulsed synchrocyclotrons can be used for the purpose of FLASH research and treatment.
研究在扩展布拉格峰（SOBP）处给予的FLASH级剂量率对小鼠正常组织损伤的影响。
50只无肿瘤小鼠接受腹部照射，30只接受FLASH剂量率（100 Gy/s）照射，20只接受传统剂量率（0.1 Gy/s）照射。总剂量值范围为10至19 Gy，由同步回旋加速器质子治疗系统在单个点给予。以腹部为中心，所给予的准直野为直径11 mm的圆，从入射到远端80%剂量的水等效深度为2.4 cm。使用一个脊形滤波器在整个2.4 cm范围内提供剂量均匀性。FLASH和传统照射的空间分布相同。
在照射日期后21天跟踪总体生存率和每只小鼠的体重，并比较FLASH和传统剂量率组的LD50值。与接受传统剂量率照射的小鼠相比，接受FLASH剂量率照射的小鼠LD50值更高，生存率有10%至20%的剂量依赖性改善。在研究的每一天，FLASH组的群体生存率也更高或相当。
这些结果初步证实了布拉格峰优势与FLASH治疗对正常组织保护益处相结合的潜力。该实验还证实了脉冲同步回旋加速器可用于FLASH研究和治疗目的。
