Pulse Parameter Optimization Method for Ultra High Dose Rate Electron Treatment

Purpose: Commercial UHDR platforms deliver Ultra-High Dose Rate (UHDR) doses at discrete combinations of pulse parameters including 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 treatment configuration. The purpose of this work is to present a pulse parameter optimizer application to match intended dose and dose rate precisely and efficiently. Methods: Dose and dose rate calculation have been described for a commercial electron FLASH platform. A constrained optimization for the dose and dose rate cost function was modelled as a mixed integer problem in MATLAB (The MathWorks Inc., Version9.13.0 R2022b, Natick, Massachusetts). The beam and machine data required for the application were acquired using GafChromic film and Alternating Current Current Transformers (ACCTs). Variables for optimization included dose per pulse (DPP) for every collimator at a specific treatment configuration, PW and PRF measured using ACCT, and airgap factors. Results: Using PW, PRF, N and airgap factors as the parameters, the application was created to optimize for dose and dose rate. Largely automating dose and dose rate calculation reduces 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 safely managed. Conclusion: A pulse parameter optimization application was built in MATLAB for a commercial electron UHDR platform to increase efficiency in the dose, dose rate, and pulse parameter prescription process.