Cone beam CT verification for oesophageal cancer – impact of volume selected for image registration

Figures & data

Table I. Patients characteristics.

No. of patients	20
Male/female	14 Male
	6 Female
Age mean (range)	66 (41–84)
Pathology	12 Adenocarcinoma
	8 Squamous cell carcinoma
Stage (AJCC)	1 = I
	4 = IIa
	5 = III
Total dose delivered/fractions	54 Gy in 30# (18)
	60 Gy in 30# (2)
Tumour location	4 thoracic (mid)
	5 lower
	11 gastro-oesophageal junction
GTV length cm mean (range)	5.4 cm (3–7 cm)

Figure 1. CT and CBCT overlay in coronal and transverse and sagital plane. The area defined in yellow represents C-PTV (a), C-carina (b), C-vertebrae (c) and C-thorax (d) clipbox definition.

Table II. Summary of whole population average systematic and random translational errors.

	C-PTV			C-carina			C-thorax
	Rt/Lt	Sup/Inf	Ant/Post	Rt/Lt	Sup/Inf	Ant/Post	Rt/Lt	Sup/Inf	Ant/Post
Σ (cm)	0.14	0.26	0.14	0.19	0.23	0.26	0.15	0.26	0.12
σ (cm)	0.26	0.39	0.20	0.27	0.34	0.25	0.25	0.33	0.17
Max (cm)	0.98	1.5	0.61	0.94	1.48	0.85	0.88	1.32	0.61

Σ, systematic error; σ, random error; Rt, right; Lt, left; Sup, superior; Inf, inferior; Ant, anterior; Post, posterior.

Table III. Summary of whole population average systematic and random rotational errors.

	C-PTV			C-carina			C-thorax
	Pitch	Roll	Yaw	Pitch	Roll	Yaw	Pitch	Roll	Yaw
Σ (°)	1.12	1.26	1.20	1.45	1.58	1.26	0.55	1.33	1.01
σ (°)	0.97	1.19	1.23	1.14	1.47	1.13	0.56	0.98	1.01
Max (°)	4.7	9.0	6.8	5.8	6.7	4.6	2.5	4.4	4.5

Σ, systematic error; σ, random error.

Figure 2. Percentage of registrations within 2 mm when C-carina, C-vertebrae and C-thorax compared to C-PTV clipbox.

Figure 3. Percentage of rotations within 2 degrees when C-carina and C-thorax compared to C-PTV clipbox.