Table 1.

Measured MLC transmission ratios (TRs) for three types of MLC systems installed in five linear accelerators. The other (TR, DLG) optimization schemes refer to the optimization from typical patient plans for the Varian 120 MLC systems and the Pinnacle optimization process for the Siemens 160 MLC system

MLC System	Linac	MLC TR (%)	Optimal DLG From Test Fields (mm)	DLG From Extrapolation (mm)	(TR, DLG) From Other Optimization Schemes (%, mm)
Millennium 120	Trilogy	1.4	2.3	1.6	(1.25, 2.5)
Millennium 120	Clinac 2300 iX	1.4	2.3	1.6	(1.25, 2.5)
Millennium 120	Clinac 21 EX	1.4	2.5	1.8	Not done
High definition 120	TrueBEAM STx	1.3	0.6	0.3	(1.3, 0.8)
Siemens 160	Artiste 1	0.26	0.3	0.2	(1.24, 0.4)