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Figure 5: (a) Relative positional deviation of the four corner spots normalized with respect to the central spot for enrgies from 70.2 to 226.2 MeV at isocenter (air gap = 0) and for gantry 90°. (b) Symmetry in % of the central single spots along X and Y direction measured for 70.2–226.2 MeV at 10 MeV increment for gantry 90°and at different air gaps of 0 (isocenter), ±10 cm and ±20 cm

Figure 5: (a) Relative positional deviation of the four corner spots normalized with respect to the central spot for enrgies from 70.2 to 226.2 MeV at isocenter (air gap = 0) and for gantry 90°. (b) Symmetry in % of the central single spots along X and Y direction measured for 70.2–226.2 MeV at 10 MeV increment for gantry 90°and at different air gaps of 0 (isocenter), ±10 cm and ±20 cm