Table 1.

Spatial accuracy of the CT and the MRI scanners.

Imager		Zone 1 $|\mathbf{\Delta }\mathit{E}|$		Zone 2 $|\mathbf{\Delta }\mathit{E}|$		Zone 3 $|\mathbf{\Delta }\mathit{E}|$		Zone 4 $|\mathbf{\Delta }\mathit{E}|$
	Exact (mm)	15.56		31.11		62.23		93.34
O-arm	Point 1	15.60	0.04	31.11	0.002	62.13	0.09	93.33	0.01
	Point 2	15.59	0.03	31.19	0.08	62.22	0.01	93.33	0.01
	Point 3	15.42	0.14	31.28	0.17	62.13	0.10	93.25	0.09
	Point 4	15.45	0.11	31.19	0.08	62.05	0.18	92.99	0.35
	Average displacement (mm)	15.52	0.08	31.19	0.08	62.13	0.10	93.22	0.12
	$\pm \mathbf{SD}$ (mm)	0.05	0.03	0.04	0.03	0.04	0.04	0.08	0.08
GE Signa	Point 1	15.67	0.11	31.17	0.06	62.42	0.19	93.16	0.18
	Point 2	15.58	0.02	31.17	0.06	62.34	0.11	93.59	0.26
	Point 3	15.67	0.11	31.08	0.03	62.59	0.37	94.03	0.59
	Point 4	15.41	0.15	30.82	0.29	62.16	0.07	93.16	0.18
	Average displacement (mm)	15.48	0.10	31.06	0.11	62.38	0.19	93.48	0.30
	$\pm \mathbf{SD}$ (mm)	0.06	0.03	0.08	0.06	0.09	0.06	0.21	0.10

Note: $\text{Exact}=\text{known coordinate values}$ at each point; $|\mathrm{\Delta }E|=\text{absolute values}$ of displacement from the exact points on the phantom; Point 1, Point 2, Point 3, and $\mathrm{Point}4=\text{each measured point}$ on the phantom. The points are in the phantom as follows: Point 1 is at the corner closest to the Roman numeral indicating each zone followed by the other points, in turn, at the corner of each zone clockwise from Point 1; $\mathrm{SD}=\text{standard deviation}$.