Table 3.

Correlation between two-dimensional gamma passing rate and dose difference for patients with nasopharyngeal cancer (NPC) and oesophageal cancer

Acceptance criteria	4%/4 mm		3%/3 mm		2%/2 mm
	r	p	r	p	r	p
NPC
Point
Simulation isocentre	0.05	0.83	0.11	0.64	0.17	0.84
Calculating point	0.21	0.38	−0.10	0.69	−0.12	0.61
PTV
Dmax	−0.25	0.29	0.35	0.13	0.42	0.07
Dmean	−0.15	0.53	−0.21	0.37	−0.11	0.65
D2%	−0.21	0.38	0.24	0.32	0.33	0.15
D98%	−0.14	0.55	0.49*	0.03	0.57*	0.009
Brainstem
Dmax	0.19	0.41	0.45*	0.049	0.61*	0.004
D1%	−0.23	0.34	0.56*	0.01	0.52*	0.02
Spinal cord
Dmax	0.03	0.9	0.02	0.93	0.01	0.96
D1%	0.15	0.54	−0.38	0.10	−0.21	0.37
Right parotid
Dmean	−0.29	0.22	−0.08	0.74	−0.13	0.58
D50%	0.19	0.31	−0.24	0.30	−0.16	0.50
Left parotid
Dmean	−0.10	0.67	0.09	0.71	0.30	0.20
D50%	0.12	0.61	0.01	0.96	0.12	0.62
Oesophageal cancer
Point
Simulation isocentre	0.37	0.12	0.35	0.14	0.46	0.05
Calculating point	0.60*	0.007	0.49*	0.04	0.40	0.09
PTV
Dmax	0.01	0.97	−0.15	0.54	−0.06	0.81
Dmean	0.19	0.43	0.16	0.51	0.17	0.49
D2%	0.05	0.85	−0.11	0.65	−0.04	0.86
D98%	0.40	0.09	0.26	0.29	0.32	0.19
Spinal cord
Dmax	−0.26	0.29	−0.36	0.13	−0.14	0.57
D1%	−0.16	0.51	−0.34	0.16	−0.18	0.47
Lung
Dmean	−0.29	0.25	−0.46	0.06	−0.36	0.14
D50%	−0.31	0.21	−0.41	0.09	−0.36	0.15
Heart
Dmean	−0.17	0.52	−0.28	0.27	−0.2	0.44
D50%	−0.27	0.29	−0.24	0.35	−0.42	0.10

D_x%, dose to percentage volume; D_max, maximum dose; D_mean, mean dose; PTV, planning target volume.

Asterisks indicate statistically significant values.