2D reader for dose mapping in radiotherapy using radiophotoluminescent films

Abstract

A 2D radiophotoluminescence (RPL) acquisition system was developed in the Belgian Nuclear Research Centre (SCK•CEN) for advanced 2D dosimetry, which is particularly important during quality assurance (QA) in external beam radiotherapy. The system is characterized by testing its various dosimetric properties using Al2O3:C,Mg films.In this study, we characterize the system according to its stability, repeatability, readout speed and spatial resolution. Furthermore, the dose response for the Al2O3:C,Mg films was verified as well as its feasibility to visualize clinical beam profiles (6 MV photons) compared to the treatment planning system (TPS) and to profiles obtained with Gafchromic films (EBT3) and BaFBr films (Optically stimulated luminescence, OSL).The average RPL counts (2 × 2 cm2 readout area) showed a repeatability of 3.3% (0 Gy), 2.7% (1 Gy) and 0.4% (60 Gy), for 10 measurements. When verifying variation in individual pixel counts within the readout area, this variation is 5.0% (0 Gy), 4.2% (1 Gy) and 2.2% (60 Gy). The dose response study showed a linear behavior in the most prominent range for RT (1–10 Gy) above which a supralinear behavior is observed between 10 and 70 Gy followed by a sublinear behavior. The system has sub-millimeter spatial resolution of (0.86 ± 0.10) mm. Finally, the Al2O3:C,Mg films are able to visualize clinical beam profiles with a good agreement (within 1%) of the films compared to EBT3 and TPS.The 2D RPL system presented in this work is a stable reader with good reproducibility that requires few corrections related to the image reconstruction with potentials for the future application in QA during radiotherapy.