Table 1.

The RPC‐measured and institution treatment planning system‐calculated small field size dependence output factor values for Varian machines. The values in square brackets and parentheses beneath each energy for each field size value are the average absolute percent differences and standard deviations of the values, respectively. For each energy and field size, the number of measurements (accelerators) is also shown

Field Size $(cm\times cm)$	Varian 6MV RPC Institution		Varian 10 MV RPC Institution		Varian 15 MV RPC Institution		Varian 18 MV RPC Institution
$10\times 10$	1.000	1.000	1.000	1.000	1.000	1.000	1.000	1.000
$6\times 6$	0.938	0.945	0.959	0.964	0.963	0.964	0.969	0.971
	(0.005)	(0.008)	(0.002)	(0.003)	(0.005)	(0.007)	(0.003)	(0.006)
	[0.8%]		[0.5%]		[0.4%]		[0.5%]
	$(\mathrm{n}=127)$		$(\mathrm{n}=22)$		$(\mathrm{n}=25)$		$(\mathrm{n}=41)$
$4\times 4$	0.886	0.900	0.916	0.927	0.927	0.928	0.928	0.933
	(0.006)	(0.013)	(0.006)	(0.010)	(0.006)	(0.009)	(0.002)	(0.009)
	[1.8%]		[1.2%]		[0.7%]		[0.9%]
	$(\mathrm{n}=122)$		$(\mathrm{n}=25)$		$(\mathrm{n}=32)$		$(\mathrm{n}=37)$
$3\times 3$	0.851	0.870	0.880	0.894	0.892	0.894	0.884	0.891
	(0.007)	(0.012)	(0.006)	(0.008)	(0.006)	(0.012)	(0.005)	(0.019)
	[2.4%]		[1.6%]		[0.9%]		[1.4%]
	$(\mathrm{n}=123)$		$(\mathrm{n}=25)$		$(\mathrm{n}=31)$		$(\mathrm{n}=41)$
$2\times 2$	0.804	0.825	0.823	0.838	0.824	0.823	0.806	0.804
	(0.008)	(0.020)	(0.005)	(0.015)	(0.011)	(0.040)	(0.007)	(0.020)
	[2.9%]		[2.0%]		[2.2%]		[1.6%]
	$(\mathrm{n}=136)$		$(\mathrm{n}=23)$		$(\mathrm{n}=33)$		$(\mathrm{n}=40)$