Different setup errors assessed by weekly cone-beam computed tomography on different registration in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy

Figures & data

Figure 1 Image registration by automatic bone matching and manual fine-tuning method in head.

Notes: (A) The cross section, coronal plane, and sagittal plane in an NPC patient’s planning CT, and we use nasal septum as a bony landmark for automatic bone matching and manual fine-tuning method (the yellow frame represents registration area); (B) the cross section of the head in planning CT image; (C) the cross section of the head in cone-beam CT image; (D) a typical fusion image with planning CT. The areas circled in red indicate the primary gross volume (GTVnx).
Abbreviations: NPC, nasopharyngeal carcinoma; CT, computed tomography.

Figure 2 Image registration by automatic bone matching and manual fine-tuning method in upper neck.

Notes: (A) The cross section, coronal plane, and sagittal plane in an NPC patient’s planning CT, and we use 1–3 cervical vertebrae as a bony landmark for automatic bone matching and manual fine-tuning method (the yellow frame represents registration area); (B) the cross section of upper neck in planning CT image; (C) the cross section of upper neck in cone-beam CT image; (D) a typical fusion image with planning CT. The areas circled in red indicate the involved lymph nodes (GTVnd).
Abbreviations: NPC, nasopharyngeal carcinoma; CT, computed tomography.

Figure 3 Image registration by automatic bone matching and manual fine-tuning method in lower neck.

Notes: (A) The cross section, coronal plane, and sagittal plane in an NPC patient’s planning CT, and we use 4–6 cervical vertebrae as a bony landmark for automatic bone matching and manual fine-tuning method (the yellow frame represents registration area); (B) the cross section of lower neck in planning CT image; (C) the cross section of lower neck in cone-beam CT image; (D) a typical fusion image with planning CT. The areas circled in red indicate the involved lymph nodes (GTVnd).
Abbreviations: NPC, nasopharyngeal carcinoma; CT, computed tomography.

Figure 4 Setup errors of 30 patients in the (A) right–left direction; (B) superior–inferior direction, and (C) anterior–posterior direction (the mean ± SD).

Abbreviations: RL, right–left; SI, superior–inferior; AP, anterior–posterior; SD, standard deviation.

Table 1 The translational shifts >3 mm in RL, SI, and AP directions of head, upper neck, and lower neck

	Interfraction >3 mm (n)
	RL	SI	AP
Head	0 (0)	2 (0.5)	0 (0)
Upper neck	8 (1.3)	3 (0.5)	36 (6)
Lower neck	56 (9.3)	3 (0.5)	153 (25.4)

Note: Data in parentheses are percentages.

Abbreviations: RL, right–left; SI, superior–inferior; AP, anterior–posterior.

Table 2 Summary of interfraction translational error (mm) in each dimension

	RL	SI	AP
M	1.334	1.335	1.585
SD	0.238	0.109	0.205
Minimum	0	0	0
Maximum	6	4	9
Σ	0.708	0.433	0.896
σ	1.407	0.189	0.504
MPTV	2.788	1.215	2.593

Abbreviations: M, mean of all patients’ mean; SD, standard deviation; Σ, systematic setup uncertainty; σ, random setup uncertainty; RL, right–left; SI, superior–inferior; AP, anterior–posterior; MPTV, PTV margins.

Table 3 Analysis of variance of setup errors in different parts in RL, SI, and AP directions

	Head*	Upper neck*	Lower neck*	F/X2	P
RL	0.856±0.729	1.170±0.955	1.608±1.195	109.88a	0.000
SI	1.373±0.802	1.383±0.816	1.340±0.817	0.02b	0.982
AP	0.893±0.797	1.279±1.155	2.347±1.878	210.88a	0.000

Notes:

a Analysis of variance;

b Kruskal–Wallis H-test.

* Data presented as mean ± SD.

Abbreviations: RL, right–left; SI, superior–inferior; AP, anterior–posterior.