Table 3.

The RPC‐measured and institution treatment planning system‐calculated small field size dependence output factor values for Siemens 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.

	Siemens 6 MV		Siemens 10 MV		Siemens 18 MV
Field Size (cm X cm)	RFC	Institution	RPC	Institution	RFC	Institution
$10\times 10$	1.000	1.000	1.000	1.000	1.000	1.000
$6\times 6$	0.914	0.920	0.927	0.935	0.940	0.946
	(0.008)	(0.008)	(0.003)	(0.010)	(0.005)	(0.003)
	[0.7%]		[0.9%]		[0.6%]
	$(\mathrm{n}=13)$		$(\mathrm{n}=4)$		$(\mathrm{n}=4)$
$4\times 4$	0.855	0.863	0.877	0.884	0.891	0.896
	(0.010)	(0.009)	(0.001)	(0.012)	(0.004)	(0.003)
	[1.1%]		[1.2%]		[0.6%]
	$(\mathrm{n}=13)$		$(\mathrm{n}=4)$		$(\mathrm{n}=4)$
$3\times 3$	0.820	0.825	0.841	0.850	0.849	0.855
	(0.008)	(0.011)	(0.001)	(0.007)	(0.003)	(0.003)
	[1.3%]		[1.1%]		[0.7%]
	$(\mathrm{n}=13)$		$(\mathrm{n}=4)$		$(\mathrm{n}=4)$
$2\times 2$	0.764	0.757	0.777	0.742	0.795	0.779
	(0.010)	(0.042)	(0.005)	(0.079)	(0.004)	(0.015)
	[2.8%]		[5.8% a ]		[1.9%]
	$(\mathrm{n}=12)$		$(\mathrm{n}=4)$		$(\mathrm{n}=4)$

^aAn institution value was 25% different to the RPC‐measured value. The institution corrected its data subsequent to the RPC visit.