Medical Physics Seminar - Eric S Diffenderfer

Ionizing radiation delivered at ultra-high dose rates (UHDR) has been associated with reduced normal tissue toxicity in small animal models when compared with radiation delivered at conventional dose rates. The effect on tumor control is found to be independent of dose rate when comparing UHDR with conventional dose rates in irradiated animal tumor models. This differential normal tissue response and iso-effective tumor response has been dubbed the FLASH effect. FLASH radiation could have a potentially profound effect on cancer treatment if the technology to deliver UHDR radiation can be translated and optimized for clinical use. To this end, we have developed and validated an instrument to deliver UHDR proton beams for preclinical research in small animal models using a research proton beam line on a clinical proton radiotherapy system. We have developed several subsystems to investigate and optimize clinically relevant delivery parameters in small animal models. Among these, a dose monitoring and beam control feedback system was developed to precisely deliver proton dose at UHDR and conventional dose rate. A scattering and beam collimation system was developed to create a symmetric and uniform field with high proton use efficiency for delivering relatively large fields to small animals at all dose rates. A ridge filter was designed, and 3D printed to efficiently modulate proton beam energy and create a spread-out bragg peak. Additionally, an animal scanning system synchronized with beam delivery was developed to investigate spatially and temporally varying dose delivery on the FLASH effect.

A video of the presentation will be provided after the event.