FLASH Dose Rate Helium Ion Beams: First In Vitro Investigations.

Purpose: To establish and investigate the effects of dose, linear energy transfer (LET), and O concentration on biologic response to ultrahigh dose rate (uHDR; FLASH) helium ion beams compared with standard dose rate (SDR) irradiation.

Methods And Materials: Beam delivery settings for raster-scanned helium ions at both uHDR and SDR were tuned to achieve >100 Gy/s and ∼0.1 Gy/s, respectively.