Table 3.

Comparison of relative dose factors between water, Plastic Water, ^a and Solid Water ^b

Energy	Field size	Water	Plastic Water	Solid Water
4 MV	$5\times 5$ cm	0.946	0.954	0.955
	$20\times 20$ cm	1.057	1.046	1.045
6 MV	$5\times 5$ cm	0.943	0.945	0.945
	$20\times 20$ cm	1.054	1.047	1.049
10 MV	$5\times 5$ cm	0.934	0.938	0.939
	$20\times 20$ cm	1.056	1.048	1.051
18 MV	$5\times 5$ cm	0.917	0.916	0.919
	$20\times 20$ cm	1.070	1.065	1.071

^aCIRS, Norfolk, VA.

^bGammex rmi, Middleton, WI.