Novel Detector Characterization for an Ultrafast Linac Commissioning
Abstract
Purpose
Plastic scintillators offer fast data acquisition, small sensitive volumes suitable for small field dosimetry, and tissue equivalence, making them well suited for LINAC commissioning. This study characterizes the BluePhysics (BP) plastic scintillator for rapid commissioning workflows, focusing on dosimetric performance and agreement with a standard ionization chamber.
Methods
BP scintillator measurements were acquired on a Varian TrueBeam using photon and electron beams in an IBA water tank. Detector performance was evaluated for repeatability, dose linearity, dose-rate dependence, and angular dependence. Percent depth dose (PDD), profiles and output factor (OF) measurements were compared against an IBA cc13 ionization chamber using gamma analysis criteria (2%/2mm, 10% threshold). An empirical approach was used to optimize post-processing parameters for the scintillator detector to best match conventional IC data.
Results
For 6MV, measurement repeatability showed maximum variation of 0.47% and 0.34% at 20MU and 200MU, respectively, while angular dependence demonstrated a maximum deviation of 2.43%. Dose response was linear across low to high monitor units with R² > 0.999. Dose-rate dependence was minimal, with maximum variations of 0.71% for 6 MV FFF and 0.13% for 10 MV FFF beams. Output factors agreed with the cc13 within 0.3% down to 3 cm × 3 cm field size. Optimal signal processing was achieved using a group size of 50 and a rolling window smoothing parameter of 20. Gamma analysis demonstrated strong agreement: 6 MV FFF PDDs achieved 99% pass rates for 3×3 cm² fields, 10 MV photon profiles (30 cm × 30 cm) achieved 97.35%, and 6 MeV electron PDDs (20 cm cone) achieved 93.33%.
Conclusion
The BluePhysics plastic scintillator demonstrates suitable dosimetric performance for commissioning, including good linearity, reproducibility and minimal dose rate dependence. Strong agreement with a conventional ionization chamber supports its use for depth dose, profile measurements and OFs