Table 1.

Levels of the parameter for each beam model defined for the design of experiment.

	Level	σX (mm)	σY (mm)	DLG (mm)	T (%)
TrueBeam Tx ‐ Millennium MLC ‐ X6	1	0.7	0	0.75	1
	2	1.3	1.1	2.3	1.8
	3	1.8	1.4	3	2
TrueBeam STx ‐ 120 HD MLC ‐ X6	1	0	0	0.2	0.8
	2	0.6	0.6	1.5	1.2
	3	1.2	1.2	2.5	1.8
TrueBeam STx ‐ 120 HD MLC ‐ X6 FFF	1	0	0	0	0.8
	2	0.6	0.6	0.8	1.2
	3	1.2	1.2	1.6	1.8

σX/σY, effective target spot size in the X/Y direction; DLG, dosimetric leaf gap; T, transmission.