Emerging FLASH therapy platforms for stereotactic radiosurgery and body radiotherapy

The integration of FLASH radiotherapy with stereotactic techniques presents a promising avenue for improving therapeutic outcomes through normal tissue sparing while maintaining tumor control. However, significant technical challenges must be addressed for successful clinical implementation. This review evaluates emerging platforms and technical requirements for combining FLASH delivery with stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). While electrons have enabled extensive preclinical FLASH research, their limited penetration depth makes them unsuitable for most stereotactic applications. Photon-based systems face significant engineering challenges in achieving both FLASH dose rates (>40 Gy/s) and the beam characteristics necessary for stereotactic delivery, particularly regarding heat management and multi-angle treatment capabilities. Proton and heavy ion systems offer advantages through the Bragg peak but require substantial development to overcome technical limitations in beam delivery and scanning speeds. We evaluate emerging platforms including novel accelerator designs, beam monitoring systems, and delivery techniques aimed at clinical translation. Critical technical requirements are discussed, including specialized dosimetry systems capable of ultra-high dose rate measurements, quality assurance protocols, treatment planning systems that optimize both spatial and temporal aspects of delivery, and novel image guidance strategies.