Estimating the Accuracy of Proton Beam Dosimetry with Film Detectors

The theoretical and experimental characteristics of depth dose distributions of protons in the Bragg peak region are investigated. Results of the Monte Carlo calculations in the TOPAS MC software package and experimental data obtained from film detectors and ionization chambers at the high-current proton linear accelerator of the Institute for Nuclear Research are used. The interrelationship between the results and the applicability of these detectors for measuring the absorbed dose are considered. The calculated dose distributions are in good agreement with the dose distributions measured using the ionization chambers for the pristine and spread-out Bragg peaks. Possible interrelationship between the linear energy transfer and the accuracy of dose measurements with the film detectors is shown. The discrepancy between the readings of the film detectors in the Bragg peak region, on the one hand, and the results of calculations and measurements with the ionization chambers, on the other hand, may be important for irradiation of biological samples, in particular, in the FLASH therapy modes.