Table 2.

Normalized standard deviations of the image‐quality parameters evaluated for the Varian OBI and EPID system. Measurement units denoted in table for each parameter represent the unit used in acquiring raw data. Table results, however, are unit‐less normalized standard deviations

Planar Radiographic			kV CBCT
	kV	MV		Full‐Fan	Half‐Fan
Spatial resolution (lp/mm)			Spatial resolution (lp/mm) f
${\mathrm{f}}_{30}$	0.015	0.006	${\mathrm{f}}_{30}$	0.087	0.110
${\mathrm{f}}_{40}$	0.008	0.009	${\mathrm{f}}_{40}$	0.086	0.116
${\mathrm{f}}_{50}$	0.004	0.018	${\mathrm{f}}_{50}$	0.074	0.173
Dosimetric			HU Constancy (HU)
Dose (μGy)	0.010	0.005 a	Lung	0.023	0.038
Voltage (kVp)	0.010		Water	0.065	0.058
			Bone	0.020	0.020
			Geometric Distortion (cm)
			AP	0.005	0.006
			LAT	0.005	0.005
			Mean slice thickness	0.056	0.059
			Dose (mGy)
			Center	0.004	0.007
			Periphery	0.004	0.003
			Uniformity (HU/HU)	0.061	0.090
			Noise (HU)	0.063	0.079

^aDose mGy.