Table 3.

Differences in correction factors between central and off‐axis detectors for various gantry angles. Difference $(\%)=((\text{off}-\text{axis}\hspace{0.17em}\text{detector}\text{'}\mathrm{s}\hspace{0.17em}\text{CF}(\theta )-\text{central}\hspace{0.17em}\text{detector}\text{'}\mathrm{s}\hspace{0.17em}\text{CF}(\theta ))/\text{central}\hspace{0.17em}\text{detector}\text{'}\mathrm{s}\hspace{0.17em}\text{CF}(\theta ))\times 100$.

Photon Energy	6 MV		10 MV
Gantry angle, θ (degrees)	Average	Range	Average	Range
0°–70°	0.4	$-1.0 \text{to} 2.2$	0.6	$-1.0 \text{to} 2.4$
80°–110°	1.1	$-6.1 \text{to} 7.0$	1	$-3.7 \text{to} 6.0$
120°–180°	0.1	$-2.1 \text{to} 2.0$	0.6	$-1.3 \text{to} 1.9$