Pulse Parameter Optimization for Ultra High Dose Rate Electron Beams

Purpose: The eFLASH Mobetron delivers UHDR doses at discrete combinations of pulse width (PW), pulse repetition frequency (PRF) and number of pulses (N), which dictate unique combinations of dose and dose rates. Currently, obtaining pulse parameters for the desired dose and dose rate is a cumbersome manual process involving creating, updating and looking up values in large spreadsheets for every collimator. The purpose of this work is to present a MATLAB based pulse parameter optimizer tool to match intended dose and dose rate more precisely and efficiently. Methods: A constrained optimization problem for the dose and dose rate cost function was modelled as a mixed integer problem in MATLAB. The beam and machine data required for the software were acquired using GafChromic film and Alternating Current Current Tranformers (ACCTs), including dose per pulse for every collimator, pulse widths measured using ACCT, and air gap factors. Results: Using N, PRF, PW and air gap factors as the parameters, the software was created to optimize for dose and dose rate. By largely automating this dose calculation part, we have greatly reduced safety concerns associated with manual look up and calculation of these parameters, especially when many subjects at different doses and dose rates are to be irradiated. Conclusion: A pulse parameter optimization tool was built in MATLAB for the eFLASH Mobetron to increase efficiency in the dose, dose rate and pulse parameter prescription process