Calculation of Detector Specific Output Correction Factors Based On IAEA-AAPM TRS-483 for 6 MV Flat / Unflat Photon Beams and Comparison with Literature
Small Field Output Correction Factors
DOI:
https://doi.org/10.63187/ampas.14Keywords:
Output Correction Factors, Small Field Dosimetry, TRS-483Abstract
In the TRS-483 recommendations, output correction factors to be applied in small fields are specified as a single value for each detector and field size, regardless of the Linac model, collimation, or filtering difference. Since Scp values are used in the treatment MU value calculations, if the Correction Factors due to the detector differences are entered into the TPS incompletely, the dose calculations are incorrect in the treatment plans where small fields such as SRS, SRT, SBRT are used frequently. In our study, correction factors for 7 different detectors and 9 different field sizes (0.5, 1.0, 2.0, 2.5, 3, 3.5, 4.0, 4.5, 5.0 cm2 ) were calculated using the experimental method and their compatibility with the correction factors specific to the detectors specified in the literature was investigated. 6 WFF and 6 FFF photon output factors for IBA CC01, IBA CC04, SI Extradin A16, PTW Pinpoint 3D, PTW microDiamond, Sun Nuclear Edge and PTW SRS Diode were calculated with Daisy Chain method. It was observed that ion chambers are under-response in field sizes smaller than 3 cm2 and need a larger correction factor, whereas solid-state detectors are over-response, and needs a relatively smaller correction factor than ion chambers. The percent variation between the correction factors for the two energies 6 WFF / 6 FFF was found to be a maximum of 2% for both ion chambers and solid detectors at field sizes of 2 cm2 and larger.
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