Figure 4: (a) The profile curves calculated and measured in 4 cm × 4 cm, 10 cm × 10 cm, and 20 cm × 20 cm field sizes at the 10 cm depth in the water phantom (in the cross-line direction). (b) Gamma index values for evaluating the agreement between calculated and measured profiles in 4 cm × 4 cm, 10 cm × 10 cm, and 20 cm × 20 cm field sizes