Table 5.

Basic TPS photon beam evaluation methods and tolerances

Region	Evaluation Method	Tolerance a (consistent with IROC Houston)
High dose	Relative dose with one parameter change from reference conditions	2%
	Relative dose with multiple parameter changes b	5%
Penumbra	Distance to agreement	3 mm
Low‐dose tail	Up to 5 cm from field edge	3% of maximum field dose

^aTolerances are relative to local dose unless otherwise noted.

^bFor example, off‐axis with physical wedge.