Table 3 Average dose-volumetric parameters of the planning target volume, cauda equina, planning organ at risk volume of cauda equina, and 1.5-cm ring structure surrounding PTV for lumbar spine stereotactic ablative radiotherapy plans

PTV

Volume (cm³)

83.52 ± 46.66

-

D_98% (Gy)

14.49 ± 1.54

14.30 ± 1.50

0.015

D_90% (Gy)

17.45 ± 0.32

17.20 ± 0.45

< 0.0001

D_5% (Gy)

19.07 ± 0.24

19.49 ± 0.48

< 0.0001

D_2% (Gy)

19.21 ± 0.26

19.66 ± 0.51

< 0.0001

Maximum dose (Gy)

20.12 ± 0.43

20.55 ± 0.77

< 0.001

Minimum dose (Gy)

8.68 ± 2.04

8.45 ± 2.30

0.207

Mean dose (Gy)

18.22 ± 0.06

18.41 ± 0.17

< 0.0001

CI

0.92 ± 0.07

0.86 ± 0.10

< 0.0001

HI

0.26 ± 0.10

0.29 ± 0.10

< 0.0001

Cauda equina

Volume (cm³)

6.24 ± 2.08

-

D_1.5 cc (Gy)

6.04 ± 1.42

6.94 ± 1.75

< 0.0001

D_0.5 cc (Gy)

8.30 ± 1.51

9.39 ± 1.54

< 0.0001

D_0.1 cc (Gy)

10.37 ± 1.51

11.58 ± 1.47

< 0.0001

D_0.035 cc (Gy)

11.19 ± 1.45

12.40 ± 1.38

< 0.0001

Maximum dose (Gy)

12.93 ± 1.36

14.10 ± 1.21

< 0.0001

Mean dose (Gy)

4.56 ± 0.79

5.13 ± 1.01

< 0.0001

Cauda equina PRV

Volume (cm³)

10.08 ± 3.44

-

D_1.5 cc (Gy)

8.39 ± 1.57

9.23 ± 1.68

< 0.0001

D_0.5 cc (Gy)

10.74 ± 1.47

11.71 ± 1.43

< 0.0001

D_0.1 cc (Gy)

12.64 ± 1.33

13.53 ± 1.25

< 0.0001

D_0.035 cc (Gy)

13.33 ± 1.25

14.17 ± 1.15

< 0.0001

Maximum dose (Gy)

14.82 ± 1.17

15.52 ± 1.07

< 0.0001

Mean dose (Gy)

5.10 ± 0.85

5.60 ± 1.01

< 0.0001

Ring_1.5 cm

V_105% (cm³)

1.03 ± 1.30

3.20 ± 3.29

< 0.0001

V_110% (cm³)

0.09 ± 0.21

0.46 ± 0.79

0.008

V_115% (cm³)

0.00 ± 0.01

0.02 ± 0.07

0.155