Table 2.

The mean, system, and random error of center of mass displacements of the target volumes (mm)

Target	Direction	Mean	System error	Random error	3D vector displacement of target volumes
GTV_T	LR	1.0	1.5	2.1	3.4±2.1 (1.3, 8.1)*
	CC	−0.1	0.3	0.6
	AP	−1.3	0.5	1.0
GTV_Nl	LR	−0.5	0.6	1.5	4.3±3.0 (1.3, 8.8)
	CC	0.0	0.8	1.1
	AP	−0.8	0.6	1.1
GTV_Ns	LR	0.4	1.4	1.9	3.7±1.7 (1.7, 6.4)
	CC	−0.4	0.7	1.3
	AP	−0.1	0.6	1.2
CTV_Lr	LR	−0.1	0.4	0.8	2.5±1.5 (1.0, 5.1)
	CC	1.2	0.6	1.2
	AP	0.5	0.2	0.4

Notes:

^*Data are shown as the mean ± standard deviation, and the 95% confidence interval is shown in parentheses. A negative number means a shift to the right, caudal, and posterior in the LL, CC, and AP directions, respectively.

Abbreviations: 3D, three-dimensional; GTV_T, gross tumor volume of the primary tumor; LR, left–right; CC, cranial–caudal; AP, anterior–posterior; GTV_Nl, gross tumor volumes of the large lymph nodes; GTV_Ns, gross tumor volumes of the small lymph nodes; CTV_LR, clinical target volume of the elective region.