FLASH radiotherapy with photon beams.

Ultra-high dose rate "FLASH" radiotherapy has been shown to drastically reduce normal tissue toxicities while being as efficacious as conventional dose rate radiotherapy to treat tumors. A large number of preclinical studies describing this so-called FLASH effect have led to the clinical translation of FLASH-RT using ultra-high dose rate electron and proton beams. Although the vast majority of radiation therapy treatments are delivered using x-rays, few preclinical data using ultra-high dose rate x-ray irradiation have been published. This review focuses on different methods that can be used to generate ultra-high dose rate x-rays and their beam characteristics along with their effect on the biological tissues and the perspectives for the development of FLASH-RT with x-rays. This article is protected by copyright. All rights reserved.