Exhibit Hall | Forum 3
Purpose: The goal of this work is to determine small field output correction factors of various detectors using a commercial plastic scintillation detector as a reference and to compare values with current available data.
Methods: Small field output factor measurements of a 6 MV Flattening Filtered beam from a Varian TrueBeam linear accelerator were performed using various detectors: PTW 60019 microDiamond, IBA Razor diode, IBA Razor chamber, IBA Razor Nano chamber, Standard Imaging A26 and a 1 mm diameter by 1 mm length plastic scintillation detector from MedScint HS-RP200 research platform. Total and partial field output correction factors for the commercial scintillator have been calculated using TOPAS/GEANT4 simulation toolkit and available light production quenching data. Using calculation corrected output factors from HyperScint detector as reference, detector-specific small field output correction factors for the other detectors have been extracted. The HS-RP200 output factors are averaged over 7 independent measurement sequences with 4 different probes (uncertainty less than 0.002).
Results: Field output correction factors estimated from plastic scintillation model corrected measurements for different diamond, diodes and micro chambers are presented for a range of jaws delimited field sizes. Corrections remain small (<1.5%) over the whole set of investigated field sizes for the PTW microDiamond and IBA Razor diode. Micro chambers exhibit a significant correction factor (>1.5%) for field sizes of 1x1 cm². Comparison with available published data shows discrepancies of less than 2% for all detectors.
Conclusion: The simple and well understood composition and geometry of the scintillation detector make it ideal to be used as a reference detector for the evaluation of field output correction factors. Field size dependent correction factors have been extracted for different detectors and show limited discrepancies with current available data. This may potentially be attributed to inter detector variability or other methodological uncertainties in published data.
Funding Support, Disclosures, and Conflict of Interest: 1) The presenting author has not been financially supported by Medscint. 2)The study has been conducted in the context of the grant PSO Maturation (MEI_v-ref 53026 n-ref 12-453PSO2D) supported partly by Medscint.
Small Field Dosimetry, Plastic Scintillation Detectors, Output Factor Corrections
TH- External Beam- Photons: Small field experimental dosimetry