Abstract: One or more new metrics are introduced into the treatment planning process. More specifically, a correcting factor/metric referred to herein as the critical/repair ratio index is introduced, and/or a correcting factor/metric referred to herein as the spatial periodicity of critical isodose value is introduced. By using these metrics, the expected sparing from the spatial distribution of dose is better accounted for in treatment modalities including spatially fractionated radiation therapy (SFRT) in general and SFRT with ultra-high dose rates in particular. According to a treatment planning strategy, the target can be covered by a Spread-Out Bragg Peak, to optimize and/or homogenize the dose distribution at the target level but still benefit from the sparing effect of SFRT at the healthy tissue level. Delivery techniques include a dynamic focusing technique and a magnetic beam steering technique. Enhancing dose rate enables maximizing the peak-to-valley dose distribution with SFRT despite patient motion.

Abstract: The present disclosure relates to the field of radiotherapy, in particular, methods of and apparatus for treating cancer using ultra-high dose rate radiotherapy (FLASH). The apparatus may comprise a device configured to administer to the subject no more than five fractions of proton ultra-high dose rate radiotherapy (FLASH), said fractions having a range of radiation from 1.5 Gy to 60 Gy, collectively. The device may be configured such that the treatment is sufficient to prevent further growth of the tumor for at least 10% longer than standard of care radiotherapy, induce at least 10% more tumor regression than standard of care radiotherapy and/or delay tumor regrowth by at least about 2 months longer than standard of care radiotherapy.