Figure 4. Peripheral dose(PD) in phantom from 6 MV X-rays measured at 5 cm, 10 cm and 15 cm depth with target to chamber distance of 100 cm. Effective field size of 10 cm x 10 cm having 1 cm sweeping gap width and 0° collimator is used. PD is normalized to 100% on the central axis at depth of maximum dose of static open field.