Purpose: FLASH radiation therapy increases the therapeutic index for cancer treatment, and a threshold dose-rate of 40 Gy/s has been proposed as the lower limit for inducing the normal tissue sparing effect, also known as the FLASH effect. However, the adoption and implementation of this promising therapy has been hindered due to FLASH machine availability. Commercial options are finally reaching the market with one of the first being the FLASH Mobetron manufactured by IntraOp Medical with FLASH capabilities producing electron beams with dose rates up to 1000Gy/s.
Methods: The 9MeV conventional beam along with the 6 and 9MeV FLASH beams were commissioned. Guidelines established in AAPM’s TG-72 report were modified to account for the unique properties of the system. Percent depth dose curves (PDDs) and profiles were taken for each collimator size and beam energy at each varying pulse width and pulse repetition frequency. These measurements are validated using a multi-detector approach utilizing Gafchromic film, toroids, and ion chambers at extended SSD.
Results: The data show a high reproducibility of the FLASH beams. Maximum output variation throughout a single day was <3%. The day-to-day variation was within 1.5%. The linearity of pulse width and number of pulses was within 2%. Our results show excellent correlation between all dosimeters used.
Conclusion: The FLASH Mobetron is one of the first commercial FLASH systems available for pre-clinical and clinical translational use. Our initial measurements show that the FLASH Mobetron can produce 9MeV FLASH electron beams that are stable and reproducible. It is important to understand and optimize carefully the system’s parameters to correctly commission the Mobetron unit. This study establishes a new commissioning protocol developed specifically for electron FLASH units.