Hybrid Cerenkov-scintillation detector validation using Monte Carlo simulations

Abstract

Objective: This study aimed at investigating through Monte Carlo simulations the limitations of a novel hybrid Cerenkov-scintillation detector and the associated method for irradiation angle measurements. Approach: Using Monte Carlo simulations, previous experimental irradiations of the hybrid detector with a linear accelerator were replicated to evaluate its general performances and limitations. Cerenkov angular calibration curves and irradiation angle measurements were then compared. Furthermore, the impact of the Cerenkov light energy dependency on the detector accuracy was investigated using the energy spectra of electrons travelling through the detector. Main results: Monte Carlo simulations were found to be in good agreement with experimental values. The irradiation angle absolute mean error was found to be lesser than what was obtained experimentally, with a maximum value of 1.12 degree for the 9 MeV beam. A 0.4% increase of the ratio of electrons having an energy below 1 MeV to the total electrons was found to impact the Cerenkov light intensity collected as a function of the incident angle. The effect of the Cerenkov intensity variation on the measured angle was determined to vary according to the slope of the angular calibration curve. While the contribution of scattered electrons with a lower energy affects the detector accuracy, greatest discrepancies result from the limitations of the calculation method and the calibration curve itself. Significance: A precise knowledge of the limitations of the hybrid detector and the irradiation angle calculation method is crucial for a clinical implementation. Moreover, the simulations performed in this study also corroborates hypotheses made regarding the relations between multiple Cerenkov dependencies and observations from the experimental measurements.