Table 1.

Average values of dose–volumetric parameters of volumetric-modulated arc therapy (VMAT) and tri-Co-60 intensity-modulated radiation therapy (IMRT) plans for spine stereotactic ablative radiotherapy

Parameter	VMAT	Tri-Co-60 IMRT	p-value
Target volume
Volume (cm3)	57.6 ± 46.4	57.6 ± 46.4	–
D95% (Gy)	16.8 ± 1.2	11.4 ± 2.7	<0.0001
D90% (Gy)	17.5 ± 0.8	12.1 ± 3.0	<0.0001
D80% (Gy)	17.7 ± 0.8	12.9 ± 3.4	<0.0001
D5% (Gy)	18.4 ± 0.8	15.2 ± 4.9	0.010
D1% (Gy)	18.6 ± 0.8	15.5 ± 5.0	0.012
Maximum dose (Gy)	19.3 ± 0.9	15.9 ± 5.3	0.010
Minimum dose (Gy)	10.3 ± 3.2	9.1 ± 2.2	0.155
Mean dose (Gy)	17.8 ± 0.8	13.7 ± 3.9	<0.001
CI	0.85 ± 0.20	1.58 ± 1.29	0.020
HI	0.09 ± 0.04	0.24 ± 0.19	0.003
OAR
Spinal cord V14 Gy (cm3)	0.0 ± 0.0	0.0 ± 0.0	0.332
Spinal cord V10 Gy (cm3)	0.3 ± 0.6	0.1 ± 0.1	0.325
Spinal cord D10% (Gy)	8.2 ± 2.5	10.1 ± 0.9	0.002
Right kidney V10.6 Gy (%)	0.3 ± 0.7	0.3 ± 0.7	0.879
Right kidney V8.4 Gy (cm3)	1.3 ± 3.1	1.1 ± 3.2	0.810
Left kidney V10.6 Gy (%)	0.0 ± 0.1	0.8 ± 2.0	0.123
Left kidney V8.4 Gy (cm3)	0.8 ± 1.3	3.9 ± 11.2	0.227
Both lung $D_{1000{\text{cm}}^3}$ (Gy)	0.0 ± 0.0	0.0 ± 0.0	–
Colon V14.3 Gy (cm3)	0.0 ± 0.0	0.0 ± 0.1	0.330
Stomach V11.2 Gy (cm3)	0.4 ± 1.2	0.3 ± 1.2	0.778
Brachial plexus V14 Gy (cm3)	0.0 ± 0.0	0.0 ± 0.0	N/A
Oesophagus V11.9 Gy (cm3)	0.1 ± 0.2	0.3 ± 0.9	0.148
Cauda equina V14 Gy (cm3)	0.0 ± 0.0	0.0 ± 0.0	–
Body integral dose (Gy cm3)	16,570 ± 1768	22,087 ± 2986	0.044
GM (cm)	1.4 ± 0.4	2.2 ± 0.4	<0.001
GI	4.5 ± 0.6	7.4 ± 1.9	<0.001
Plan parameters
Spinal cord volume (cm3)	4.4 ± 2.7	1.8 ± 1.0	0.001
Beam-on time (min)	3.95 ± 1.13	48.82 ± 10.44	<0.001
Number of segments	–	8.7 ± 5.0	–
Dose gradient (%/mm)	10.0 ± 2.7	2.6 ± 2.3	<0.001

CI, conformity index; D_n%, the dose received at least n% volume of the structure; GI, gradient index; GM, gradient measure; HI, homogeneity index; OAR, organ at risk; V_nGy, the volume irradiated by least n Gy of dose.

The italic values are statistically significant values (p < 0.05).