Determination of the proton LET using thin film solar cells coated with scintillating powder

摘要

Abstract Purpose The amount of luminescent light detected in a scintillator is reduced with increased proton linear energy transfer (LET) despite receiving the same proton dose, through a phenomenon called quenching. This study evaluated the ability of a solar cell coated with scintillating powder (SC‐SP) to measure therapeutic proton LET by measuring the quenching effect of the scintillating powder using a solar cell while simultaneously measuring the dose of the proton beam. Methods SC‐SP was composed of a flexible thin film solar cell and scintillating powder. The LET and dose of the pristine Bragg peak in the 14 cm range were calculated using a validated Monte Carlo model of a double scattering proton beam nozzle. The SC‐SP was evaluated by measuring the proton beam under the same conditions at specific depths using SC‐SP and Markus chamber. Finally, the 10 and 20 cm range pristine Bragg peaks and 5 cm spread‐out Bragg peak (SOBP) in the 14 cm range were measured using the SC‐SP and the Markus chamber. LETs measured using the SC‐SP were compared with those calculated using Monte Carlo simulations. Results The quenching factors of the SC‐SP and solar cell alone, which were slopes of linear fit obtained from quenching correction factors according to LET, were 0.027 and 0.070 μm/keV (R2: 0.974 and 0.975). For pristine Bragg peaks in the 10 and 20 cm ranges, the maximum differences between LETs measured using the SC‐SP and calculated using Monte Carlo simulations were 0.5 keV/μm (15.7) and 1.2 keV/μm (12.0), respectively. For a 5 cm SOBP proton beam, the LET measured using the SC‐SP and calculated using Monte Carlo simulations differed by up to 1.9 keV/μm (18.7). Conclusions Comparisons of LETs for pristine Bragg peaks and SOBP between measured using the SC‐SP and calculated using Monte Carlo simulations indicated that the solar cell‐based system could simultaneously measure both LET and dose in real‐time and is cost‐effective.