BEAM MATCHING EVALUATION OF TWO SIMILAR LINEAR ACCELERATORS

To evaluate the beam-matching of two Siemens Primus medical linear accelerators (Linacs), the output factor (Sc,p), wedge factor, quality index (TPR20/10), percentage depth dose (PDD) and beam profiles were compared for 6 and 15 MV photon beams. The output factor, the PDD and the beam profile for electron beam compared for 5, 7, 8, 10 and 12 MeV electron beams. The gamma (γ) analysis of 2 mm/2% and 3 mm/3% was performed. According to the measurements, it can be said that 6 MV photon beams in all field sizes (except 4 × 4 cm2) are beam matched. For 15 MV, although the PDDs were matched in all field sizes (except 4 × 4 cm2) for both 2 mm/2% and 3 mm/3% γ criteria, beam profiles in field sizes larger than 10 × 10 cm2 for 3 mm/3% and in field sizes larger than 8 × 8 cm2 for 2 mm/2% were not matched. The electron beams in all applicator sizes (except 5 × 5 cm2 applicator) pass the acceptance γ criteria of 3 mm/3% (γ < 1). Electron beams do not fulfill beam matched in case of the acceptance γ criteria of 2 mm/2%.