An investigation of collimator head scatter with columnar miniphantom

The initial reason for introducing output factor in air is for the determination of phantom scatter factor (Sp). The most common method involves the measurement of the total scatter factor, Scp , in a phantom and the head-scatter factor output factor, Scp. The phantom scatter, Sp, is then calculated as Sp = Scp/Sc. AAPM Task Group 74 report recommends that build up caps with sufficient lateral and longitudinal thicknesses to eliminate electron contamination and maintain transient electron equilibrium, be used for the measurement of Sc. These are generally called as columnar miniphantoms