SU‐F‐T‐561: Energy Dependence of a Scintillation Detector

Abstract

Purpose:To investigate the response and dose rate dependence of a scintillation detector over a wide energy range.Methods:The energy dependence of W1 scintillation detector was tested with: 1) 50–225 keV beams generated by an animal irradiator, 2) a Leksell Gamma Knife Perfexion Co‐60 source, 3) 6MV, 6FFF, 10FFF and 15MV photon beams, and 4) 6–20MeV electron beams from a linac. Calibrated linac beams were used to deliver 100 cGy to the detector at dmax in water under reference conditions. The gamma‐knife measurement was performed in solid water (100 cGy with 16mm collimator). The low energy beams were calibrated with an ion chamber in air (TG‐61), and the scintillation detector was placed at the same location as the ionization chamber during calibration. For the linac photon and electron beams, dose rate dependence was tested for 100–2400 and 100–800 MU/min.Results:The scintillation detector demonstrated strong energy dependence in the range of 50–225keV. The measured values were lower than the delivered dose and increased as the energy increased. Therapeutic photon beams showed energy independence with variations less than 1%. Therapeutic electron beams displayed the same sensitivity of ∼2–3% at their corresponding dmax depths. The change in dose‐rate of photon and electron beams within the therapeutic energy range did not affect detector output (<0.5%). Measurements acquired with the gamma knife showed that the output data agreed with the delivered dose up to 3%.Conclusion:W1 scintillation detector output has a strong energy dependence in the diagnostic and orthovoltage energy range. Therapeutic photon beams exhibited energy independence with no observable dose‐rate dependence. This study may aid in the implementation of a scintillation detector in QA programs by providing energy calibration factors.