Determination of correction factors in small MLC-defined fields for the Razor and microSilicon diode detectors and evaluation of the suitability of the IAEA TRS-483 protocol for multiple detectors.

ABSTRACT

Small field output factors for Multileaf collimator (MLC)-defined field sizes between 0.5 × 0.5 cm2 and 3 × 3 cm2 were measured with six different detectors for a Varian TrueBeam in 6-MV, 6-FFF, 10-MV, and 10-FFF photon beams. Correction factors k Q clin , Q ref f clin , f ref $k_{{Q_{{\rm{clin}}}},{Q_{{\rm{ref}}}}}^{{f_{{\rm{clin}}}},{f_{{\rm{ref}}}}}$ from the IAEA publication TRS-483 were used to correct the measured output factors. The corrected output factors from the six detectors were used to calculate correction factors for the PTW microSilicon T60023 (PTW, Freiburg, Germany) and IBA Razor (IBA Dosimetry, Schwarzenbruck, Germany) detectors. The uncertainty of the output and correction factors in this study was calculated and the calculations presented in detail. The application of the TRS-483 correction factors significantly reduced the variation in output factors between the various detectors, with the exception of the PTW 60016 diode in 6-MV and 6-FFF beams, and the IBA PFD in 10-MV and 10-FFF beams. Correction factors calculated for the Razor agreed within 2.9% of existing literature for all energies, while the microSilicon correction factors agreed within 1.6% to the literature for 6-MV beams. The uncertainty in the microSilicon and Razor correction factors was calculated to be less than 0.9% (k = 1). This study shows that TRS-483 correction factors reduce the variation in output factors between the detectors used in this study and presents a suitable method for determining correction factors for detectors with unpublished values.