Poster - 16: Time-resolved diode dosimetry for in vivo proton therapy range verification: calibration through numerical modeling

Purpose: A method to refine the implementation of an in vivo, adaptive proton therapy range verification methodology was investigated. Simulation experiments and in-phantom measurements were compared to validate the calibration procedure of a time-resolved diode dosimetry technique. Methods: A silicon diode array system has been developed and experimentally tested in phantom for passively scattered proton beam range verification by correlating properties of the detector signal to the water equivalent path length (WEPL). The implementation of this system requires a set of calibration measurements to establish a beam-specific diode response to WEPL fit for the selected 'scout' beam in a solid water phantom. This process is both tedious, as it necessitates a separate set of measurements for every 'scout' beam that may be appropriate to the clinical case, as well as inconvenient due to limited access to the clinical beamline. The diode response to WEPL relationship for a given 'scout' beam may be determined within a simulation environment, facilitating the applicability of this dosimetry technique. Measurements for three 'scout' beams were compared against simulated detector response with Monte Carlo methods using the Tool for Particle Simulation (TOPAS). Results: Detector response in water equivalent plastic was successfully validated against simulation for spread out Bragg peaks of range 10 cm, 15 cm, and 21 cm (168 MeV, 177 MeV, and 210 MeV) with adjusted R² of 0.998. Conclusion: Feasibility has been shown for performing calibration of detector response for a given 'scout' beam through simulation for the time resolved diode dosimetry technique.