Radiation safety of ultra-high dose rate electron accelerators for FLASH radiotherapy.

Background: An ultra-high dose rate (UHDR) electron accelerator for FLASH radiotherapy (RT) produces very intense bremsstrahlung by the interaction of the electron beam with objects both inside and outside of the accelerator. The bremsstrahlung dose per pulse is typically 1-2 orders of magnitude larger than that of conventional RT x-ray treatment of the same energy, and for electron energies above 10 MeV, the bremsstrahlung produces substantially more induced radioactivity outside the accelerator than for conventional RT. Therefore, a thorough radiation safety assessment is mandatory prior to the operation of a UHDR electron accelerator.

Dependence of cell survival on instantaneous dose rate of a linear accelerator.

Background And Purpose: With the development of flattening filter-free linear accelerators for radiotherapy, the instantaneous dose rate has increased by approximately a factor 4. This leads to the question of whether there may be a radiobiological consequence. The present study investigates the radiobiological effect of this high instantaneous dose rate on two cell lines.