Table 2.

The estimated relative drifts of the imaging geometry for the displaced phantoms with different magnitudes of displacement at four principal orthogonal gantry angles. ΔR, Δz, and ΔF are the deviation of the rotation radius, deviation from the rotation plane and deviations of the source-to-detector distance, respectively. Δu and Δv are the two translational offsets of the detector in the uv plane, respectively.

Phantom shift (mm)	Gantry angle (°)	ΔR (mm)	Δz (mm)	ΔF (mm)	Δu (mm)	Δv (mm)
Δx=−5.0 Δy=−5.0 Δz=−5.0	0	3.7	−5.4	−0.2	4.6	5.3
	90	4.5	−5.1	0.0	−3.9	5.4
	180	−4.2	−5.4	−0.2	−4.5	5.3
	270	−4.6	−5.6	0.1	4.0	5.2
Δx=5.0 Δy=5.0 Δz=5.0	0	−5.6	4.6	0.0	−4.6	−4.8
	90	−4.5	4.8	0.0	5.6	−4.8
	180	5.4	4.8	−0.2	4.7	−4.8
	270	4.9	4.7	0.2	−5.5	−4.8
Δx=10.0 Δy=10.0 Δz=10.0	0	−8.4	9.7	0.0	−9.7	−9.9
	90	−9.2	10.2	0.2	8.6	−9.8
	180	8.4	10.4	−0.3	9.5	−9.6
	270	9.9	8.9	−0.4	−8.4	−10.4