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Practical Aspects of FLASH - What Physicists Should Know

P Maxim1*, M Bazalova-Carter2*, J Metz3*, (1) Indiana University, Indianapolis, IN, (2) University of Victoria, Victoria, BC, CA, (3) University of Pennsylvania, Philadelphia, PA


(Tuesday, 7/14/2020) 10:30 AM - 11:30 AM [Eastern Time (GMT-4)]

Room: Track 5

Recent in vivo studies demonstrated that ionizing radiation at ultra-high dose rates (UHDR) within 0.5 s (FLASH) to cancerous tissues inhibits tumor growth equally as in conventional therapy, but with enhanced healthy tissue sparing (Favaudon et al. 2014). This FLASH effect could enable a dose increase without additional complications, widening the therapeutic window.

The field of FLASH is rapidly expanding to support many pre-clinical studies. Indeed, the first human FLASH treatment is already reported (Bourhis et al. 2019). Medical physicists have a crucial role in the continued development of FLASH. Therefore, awareness is needed about the technical aspects of FLASH, including production methods with all radiation qualities, in-vivo experimental setups, biophysics, and reliable dosimetry. Additional considerations exist as FLASH transitions from pre-clinical to clinical use.

The current status and future outlook of delivery FLASH RT delivery systems will be presented, including x-ray, electron, and proton systems. The physics parameters are of utmost importance and will be discussed here. While FLASH-RT has been mainly characterized using the mean dose-rate (= 40 Gy/s for FLASH-RT vs. = 0.01 Gy/s for CONV-RT), this definition has proven to be overly simplistic. The full characterization of FLASH-RT is much more complicated as it involves several inter-dependent physics parameters that need to be adequately recorded for analysis and interpretation of the data. An overview will be provided here.

Details will be provided on the practical aspects of FLASH irradiation and dosimetry. The feasibility of various dosimeters for ultrahigh dose rate measurements will be described, and their advantages and disadvantages will be discussed. FLASH (electron, proton, and photon) beam properties in terms of beam time structure and beam control, beam flatness, and tissue penetration will be presented. Practical aspects of setup for cell and animal experiments, in terms of beam dosimetry, targeting, and shielding, will also be discussed.

Discussion of relevant pre-clinical results and the path to human trials, including disease site selection and prospective protocol development, must also be prepared.

The educational goals are:
1. Understand the different types of FLASH beam production systems and their critical parameters.
2. Understand how to perform FLASH dosimetry.
3. Understand what aspects must be considered in developing FLASH clinical trials.



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