Radiation chemists have been routinely using high-dose microsecond-pulsed irradiation for almost 60 years, involving many thousands of studies, in the technique of “pulse radiolysis”. This involves dose rates broadly similar to the FLASH regimen now attracting interest in radiotherapy and radiobiology. Using the experience gained from radiation chemistry, two scenarios are examined here that may provide a mechanistic basis for any differential response in normal tissues versus tumors in FLASH radiotherapy. These are: 1. possible depletion of a chemical critical to the response to radiation, and 2. radical–radical reactions as a possible cause of effects occurring mainly with high-intensity pulsed radiation. The evidence for changes in relative levels of so-called “reactive oxygen species” produced after irradiation using FLASH versus conventional irradiation modalities is also examined.

近 60 年来，辐射化学家一直在常规使用高剂量微秒脉冲辐射，涉及“脉冲辐射分解”技术的数千项研究。这涉及到与 FLASH 方案大致相似的剂量率，现在引起了放射治疗和放射生物学的兴趣。使用从放射化学中获得的经验，这里检查了两种情况，它们可以为正常组织与 FLASH 放射治疗中肿瘤的任何差异反应提供机制基础。它们是：1. 对辐射响应至关重要的化学物质可能耗尽，以及 2. 自由基-自由基反应作为主要发生在高强度脉冲辐射中的效应的可能原因。