TABLE 7.

Heterogeneous TPS photon beam validation checks

#	Objective	Examples	Tolerances a	References
6.1	Validate planning system reported electron (or mass) densities against known values	CT‐density calibration for air, lung, water, dense bone, and possibly additional tissue types	–	TG‐65, 47 IAEA TRS‐430 3
6.2	Heterogeneity correction distal to lung tissue	5 × 5 cm2, measure and calculate dose ratio above and below heterogeneity, outside of the buildup region	3%	IAEA TRS‐430, 3 Carrasco et al. 43

^a Tolerances are relative to local dose unless otherwise noted.