Purpose: Surrogate in vivo assays for several different types of radiobiological damage mechanisms are needed to allow for objective quantitative comparisons between different radiotherapeutic modalities such as FLASH or different radiation types. These quantitative assays would allow for better optimization of the therapeutic ratio of damage in tumors relative to normal tissue.
Methods: The molecular optical reporters Acridine Orange, Amplex Red, and Oxygen consumption each correspond to a different methodology of detecting radiation induced damage, including DNA damage, hydrogen peroxide production and peroxide production, respectively. These reporters were injected into biological media (aqueous proteins, ex vivo tissues, lipid-based tissue phantoms, and tumor tissue). Each optical sensor provides information about the components of radiation induced damage that are most relevant to comparing radiation treatments. The tissues were irradiated with various types of radiation, conformality of radiation, and at varying dose rates. The various irradiated tissues were then analyzed for fluorescence emission to monitor the activation of the respective optical reporters as a result of radiation induced biological damage.
Results: Each optical reporter’s resulting spectra were analyzed and used as a means of quantifying the respective radiation damage in tissue. The contributions of DNA damage, water radiolysis and protein/lipid peroxidation were quantified for conventional dose response.
Conclusion: This work examines those crucial optical reporters that possess the potential for use in documenting radiation damage and can translate from in vitro assay to in vivo assay, providing a bridge to understanding the radiobiology of treatment choices. Perhaps most importantly, these assays have significantly smaller error bars than biological function assays, and so their use can lead to assays with lower numbers of animals and better accuracy.
Radiation Effects, Fluorescence, Radiobiology