A Silicon Photodiode Coupled with a Plastic Scintillator As a Radiation Therapy Detector
Abstract
Purpose
This study investigates the performance of silicon semiconductor detectors in combination with a plastic scintillation detector (PSD) for measuring photon beam doses under clinically relevant conditions.
Methods
Four types of silicon photodiodes with different sensitivities were coupled to a 1 cm × 1 cm × 1 cm PSD, and their responses to photon beams were compared. The most efficient photodiode was further evaluated with a 0.5 mm-thick PSD. Dose linearity, average dose rate, and instantaneous dose rate dependencies of the detector response, as well as the percentage depth dose (PDD) were assessed for 6 MV, 6 MVFFF (Flattening Filter-Free), and 10 MV photon beams. Additionally, the small field output factors for 6 MV and 6 MVFFF photon beams were measured using the optimized thickness of the PSD. The in-vivo test measurements with and without a 0.5 cm bolus on top of the detector were performed.
Results
Results showed that the detector response is linear with the dose increase, and it changes within 0.25% and 0.11% for average and instantaneous dose rate variations, respectively. The PDD and small field output factor measurement results were in good agreement with other methods. The response of the detector exhibited a variation of less than 3.14\% across all beam energies investigated in this study. The in-vivo measurements with the bolus on top of the detector were in good agreement with the radiochromic film (RCF) measurements, with a 2.86% difference.
Conclusion
This study supports the use of a silicon photodiode coupled with a PSD as a flexible, bias-free, and energy-stable radiation detector. Its high spatial resolution makes it a promising candidate for routine quality assurance, small field dosimetry, and potentially in-vivo measurements in radiation therapy.