Institute of Radiation Physics, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Radiother Oncol. 2022 Oct;175:203-209. doi: 10.1016/j.radonc.2022.08.023. Epub 2022 Aug 27.
We describe a multicenter cross validation of ultra-high dose rate (UHDR) (>= 40 Gy/s) irradiation in order to bring a dosimetric consensus in absorbed dose to water. UHDR refers to dose rates over 100-1000 times those of conventional clinical beams. UHDR irradiations have been a topic of intense investigation as they have been reported to induce the FLASH effect in which normal tissues exhibit reduced toxicity relative to conventional dose rates. The need to establish optimal beam parameters capable of achieving the in vivo FLASH effect has become paramount. It is therefore necessary to validate and replicate dosimetry across multiple sites conducting UHDR studies with distinct beam configurations and experimental set-ups.
Using a custom cuboid phantom with a cylindrical cavity (5 mm diameter by 10.4 mm length) designed to contain three type of dosimeters (thermoluminescent dosimeters (TLDs), alanine pellets, and Gafchromic films), irradiations were conducted at expected doses of 7.5 to 16 Gy delivered at UHDR or conventional dose rates using various electron beams at the Radiation Oncology Departments of the CHUV in Lausanne, Switzerland and Stanford University, CA.
Data obtained between replicate experiments for all dosimeters were in excellent agreement (±3%). In general, films and TLDs were in closer agreement with each other, while alanine provided the closest match between the expected and measured dose, with certain caveats related to absolute reference dose.
In conclusion, successful cross-validation of different electron beams operating under different energies and configurations lays the foundation for establishing dosimetric consensus for UHDR irradiation studies, and, if widely implemented, decrease uncertainty between different sites investigating the mechanistic basis of the FLASH effect.
我们描述了一种超高剂量率（UHDR）（>= 40 Gy/s）照射的多中心交叉验证，以便在水吸收剂量方面达成剂量学共识。UHDR 是指比传统临床束高出 100-1000 倍的剂量率。由于已报道 UHDR 照射会诱导 FLASH 效应，即在常规剂量率下正常组织的毒性降低，因此这种超高剂量率照射已成为研究热点。建立能够实现体内 FLASH 效应的最佳光束参数变得至关重要。因此，有必要验证和复制具有不同光束配置和实验设置的多个进行 UHDR 研究的站点的剂量学。
使用具有圆柱形腔（直径 5 毫米，长 10.4 毫米）的定制立方体形体 phantom，旨在容纳三种类型的剂量计（热释光剂量计（TLDs）、丙氨酸小球和 Gafchromic 胶片），在瑞士洛桑 CHUV 的放射肿瘤学系和加利福尼亚斯坦福大学的各种电子束下，以 UHDR 或常规剂量率进行预期剂量为 7.5 至 16 Gy 的照射。
所有剂量计的重复实验之间获得的数据非常吻合（±3%）。一般来说，胶片和 TLDs 彼此之间更为一致，而丙氨酸在预期剂量和测量剂量之间提供了更接近的匹配，但与绝对参考剂量有关的某些注意事项除外。
总之，不同电子束在不同能量和配置下的成功交叉验证为 UHDR 照射研究建立剂量学共识奠定了基础，如果得到广泛实施，将降低研究 FLASH 效应机制基础的不同站点之间的不确定性。
