6 MV flat ve unflat foton demetleri için küçük alan output düzeltme faktörlerinin IAEA-AAPM TRS-483'e göre farklı detektörler için hesaplanması ve literatür ile karşılaştırılması

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. For small fields where LCPE is lost, dosimetric measurements are seriously affected by the presence of the detector used in the absorbed dose measurements resulting in problems like Volume Averaging and Perturbation effects. 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 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 MV WFF and FFF photon output factors for CC01, CC04, Extradin A16, Pinpoint 3D, microDiamond, Edge and SRS Diode were calculated with Daisy Chain method using the intermediate field. Correction factors were found for each detector using the calculated field output factor for the EBT3 film. All measurements were performed on the Versa HD system. The field size of 4 x 4 cm2 and a CC13 ion chamber were used for intermediate-field calculations. 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 need 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. There was a significant difference between the correction factors found for all detectors we used in our study for both energies in the field sizes smaller than 2 cm2.