Table 2.

Comparison between the calculated (AAA and AXB) and measured percent depth dose (PDD) at point Q in Phantom B (see Fig. 1(b)) for air gap thicknesses of 4, 6, and 10 cm. (6 MV photon beam, 100 cm SSD, 200 monitor units, $5\times 5\hspace{0.17em}{\text{cm}}^2$ and $10\times 10\hspace{0.17em}{\text{cm}}^2$ open field sizes.)

Field Size: $5\times 5\hspace{0.17em}{\text{cm}}^2$
	Chamber	AAA		AXB
Air Gap (cm)	PDD (%)	PDD (%)	Δ a (%)	PDD (%)	Δ a (%)
4	74.5	77.5	4.1	75.2	0.9
6	69.4	74.2	6.9	70.1	1.1
10	61.7	69.4	12.5	62.4	1.0
Field Size: $10\times 10\hspace{0.17em}{\text{cm}}^2$
	Chamber	AAA		AXB
Air Gap (cm)	PDD (%)	PDD (%)	Δ a (%)	PDD (%)	Δ a (%)
4	78.4	79.5	1.4	77.1	$-1.7$
6	74.2	76.2	2.6	73.3	$-1.3$
10	66.8	71.4	6.8	67.1	0.4

^{a a} A (PDD)

$\text{AAA}=\text{anisotropic analytical algorithm}$; $\text{AXB}=\text{Acuros XB algorithm}$; $\text{PDD}=\text{percent depth dose}$.