PEERing into the future: benchmarking the ANSTO Australian synchrotron’s very-high-energy electron linac for ultra-high dose-eate, in vivo FLASH radiotherapy research

Background/Objectives: The PEER beamline at the ANSTO Australian Synchrotron has been developed to enable VHEE FLASH radiotherapy studies, both dosimetric and biological. Featuring a 100 MeV electron linac, it delivers single or multi-pulse irradiations consisting of 100 ps bunches with a 2 ns spacing, resulting in average dose-rates and instantaneous dose-rates as high as 108 Gy/s and 109 Gy/s, respectively. Much work has been conducted to realise a stable accelerator facility, complete with the tooling and diagnostics required to undertake such studies. However, to truly confirm its suitability required a successful biological benchmarking. Methods: Three cell lines were irradiated utilising real-time dosimetry to compare linear quadratic cell survival curves with other facilities. Also, mouse cadavers were transported and irradiated, mimicking live animals, to assess the feasibility and logistics of small animal experiments. Results: By comparing the trends of the linear quadratic model, evident in the α and β parameters, the PEER cell survival results were shown to be in agreement with VHEE results from the ARES beamline at DESY, Hamburg, Germany. Evident in the survival trends, VHEE produced more cell sparing in all cell lines compared to 2 Gy/s X-rays delivered on the IMBL, another beamline at the Australian Synchrotron. The results of the mouse cadaver irradiations showed that PEER can safely and efficiently irradiate small animals. Conclusions: The PEER beamline is shown to possess suitable capabilities, including real-time dosimetry, repeatable alignment, and linac diagnostics, rendering it suitable for future in vivo VHEE UHDR FLASH radiotherapy investigations.