氧测量综述及其与FLASH放疗机制的相关性
Review of oxygen measurement and relevance to the mechanisms of FLASH radiotherapy
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中文总结 AI 辅助
综述FLASH放疗中正常组织相对受保护现象的潜在机制，综合体内氧测量技术证据，强调其能力与局限，总结皮肤关键实验，表明FLASH效应与剂量、氧及辐射化学相互作用有关，还涉及清除变化致生物反应改变。
中文摘要 AI 辅助
FLASH放疗是一种现象，即与临床使用的传统剂量率相比，使用超高剂量率时正常组织相对受保护。尽管进行了广泛研究，其潜在机制仍未得到解释。在提出的假设中，组织氧一直是核心主题，因为氧是已知调节辐射诱导损伤的最主要因素。涉及FLASH保护的因素包括氧的基线分压、瞬态辐射分解氧消耗以及活性氧化学中随剂量率变化的氧依赖性变化。本综述综合了关于体内氧测量技术的现有证据，强调了它们在捕捉组织氧合的空间和时间异质性方面的能力和局限性。总结并解释了皮肤方面的关键实验研究，通过改变吸入氧气和血管钳夹干预来调节氧水平，表明FLASH效应仅在中等基线pO2（常氧或轻度低氧）值时发生，而在缺氧或高氧时不发生。超高剂量率照射期间氧消耗的直接测量是可能的，这是对患者辐射化学的首批原位测量之一。同时，快速体外辐射化学分析的最新进展表明，超高剂量率照射会改变自由基产率，有利于增加溶剂化电子的产生并减少羟基自由基介导的损伤。综合现有数据表明，FLASH保护效应源于所传递的剂量和剂量率、局部氧可用性和辐射化学之间的相互作用，以及清除方面的组织特异性变化，导致在从传统剂量率到超高剂量率转变过程中生物反应发生改变。
英文摘要
FLASH radiotherapy (FLASH-RT) is the phenomenon of relative sparing of normal tissue when ultra-high dose rates (UHDR) are used compared with conventional dose rates (CDR) as clinically used. Despite extensive investigation, the underlying mechanisms remain unexplained. Among the proposed hypotheses, tissue oxygen has consistently been a central theme because oxygen is the most dominant factor known to modulate radiation-induced damage. The factors implicated in FLASH sparing include the baseline partial pressure of oxygen (pO2), transient radiolytic oxygen consumption (ROC), and oxygen-dependent changes in the chemistry of reactive oxygen species (ROS) that vary with dose rate. This review synthesizes current evidence on in vivo oxygen measurement techniques, highlighting their capabilities and limitations in capturing the spatial and temporal heterogeneity of tissue oxygenation. Key experimental studies in skin are summarized and interpreted by modulating oxygen levels via changes in inspired oxygen gas and vascular clamping interventions, demonstrating that the FLASH effect occurs only at intermediate baseline pO2 (normoxic or slightly hypoxic) values, but not at hypoxia or hyperoxia. Direct measurement of oxygen consumption during UHDR irradiation is possible, providing one of the first in situ measurements of radiation chemistry in patients. In parallel, recent advances in fast in vitro radiation chemistry assays indicate that UHDR irradiation alters radical yields, favoring increased production of solvated electrons and reduced hydroxyl radical mediated damage. Taken together, the available data suggest that the FLASH sparing effect arises from an interplay among the delivered dose and dose rate, local oxygen availability, and radiation chemistry, with tissue-specific variation in scavenging, leading to altered biological responses across the CDR-to-UHDR shift.
