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Figure 4: In-air spot size represented by one sigma (1 σ) of X profile (a) and Y profile (b) of the central spot at isocenter for various air gap of 0 (isocenter) cm, ±10 cm and ±20 cm for proton energies ranging from 70.2 to 226.2 MeV in 10 MeV increment

Figure 4: In-air spot size represented by one sigma (1 σ) of X profile (a) and Y profile (b) of the central spot at isocenter for various air gap of 0 (isocenter) cm, ±10 cm and ±20 cm for proton energies ranging from 70.2 to 226.2 MeV in 10 MeV increment