Output factor

Output factor is the ratio of the dose rate of a given field size to the dose rate of the reference field size.

the output fator is usually normalized or referenced to a 10x10cm field size, so there it will be 1.0

For fields sizes smaller than 10x10, the output factor is <1.0 because of a decrease in scatter as the collimator setting is decreased.

For field sizes >10x10 the output factor is >1.0 because of an increase in scatter as the collimator setting is increased.