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Table 3 Normal brain tissue sparing dose-volume comparisons

From: Dosimetric impact of reduced nozzle-to-isocenter distance in intensity-modulated proton therapy of intracranial tumors in combined proton-carbon fixed-nozzle treatment facilities

Volume of interest/dosimetric index

Absolute difference

Relative percentage difference

p

Whole brain

  Dnear-max [Gy(RBE)]

0.1

(−0.4÷3.0)

0.3

(−0.7÷8.5)

0.013*

  Dmean [Gy(RBE)]

1.0

(0.5÷1.6)

12.5

(9.2÷16.0)

0.001*

  V1% [%]

6.9

(4.1÷8.6)

16.7

(10.4÷21.0)

<0.001*

  V2% [%]

6.3

(3.4÷7.6)

15.2

(10.2÷19.9)

<0.001*

  V10% [%]

4.0

(2.4÷5.0)

13.6

(8.0÷18.4)

<0.001*

  V60% [%]

1.1

(0.2÷2.0)

11.3

(6.4÷16.4)

<0.001*

  V80% [%]

0.4

(0.1÷1.2)

6.3

(2.0÷12.1)

<0.001*

  V95% [%]

0.0

(−0.3÷0.3)

1.3

(−3.8÷7.0)

0.212

Brainstem

  Dnear-max [Gy(RBE)]

0.0

(−0.2÷1.1)

0.0

(−0.4÷2.1)

0.173

  Dmean [Gy(RBE)]

2.9

(1.0÷5.0)

16.2

(2.6÷30.9)

<0.001*

  V2% [%]

9.6

(0.0÷22.5)

14.0

(0.0÷27.0)

0.002*

  V10% [%]

7.9

(0.6÷20.1)

14.8

(0.6÷31.1)

<0.001*

  V60% [%]

5.5

(2.0÷8.8)

17.6

(3.8÷34.4)

<0.001*

  V80% [%]

2.5

(0.3÷6.7)

17.2

(0.5÷40.0)

<0.001*

  V95% [%]

0.6

(−0.6÷2.7)

9.1

(−14.4÷30.7)

0.017 *

Chiasm

  Dnear-max [Gy(RBE)]

0.0

(−1.5÷4.07)

0.0

(−2.9÷9.9)

0.695

  Dmean [Gy(RBE)]

0.1

(−1.2÷4.7)

0.2

(−2.5÷26.4)

0.077

  V2% [%]

0.0

(0.0÷14.6)

0.0

(0.0÷15.8)

0.5

  V10% [%]

0.0

(0.0÷13.6)

0.0

(0.0÷17.7)

0.185

  V60% [%]

0.0

(0.0÷13.3)

0.0

(0.0÷59.9)

0.050

  V80% [%]

0.0

(0.0÷7.0)

0.0

(0.0÷64.5)

0.030*

  V95% [%]

0.0

(−5.1÷8.7)

0.0

(−158.5÷26.7)

0.147

Left temporal lobe

  Dnear-max [Gy(RBE)]

1.1

(−0.1÷5.3)

2.7

(−0.2÷18.0)

0.001*

  Dmean [Gy(RBE)]

1.3

(0.5÷2.7)

9.7

(5.8÷27.4)

<0.001*

  V2% [%]

6.2

(0.8÷15.4)

8.8

(0.8÷38.2)

<0.001*

  V10% [%]

4.7

(1.4÷9.7)

7.2

(1.5÷40.0)

<0.001*

  V60% [%]

1.2

(0.0÷5.5)

13.1

(0.0÷63.9)

0.002*

  V80% [%]

0.4

(−0.0÷4.0)

11.3

(−2.0÷33.3)

0.003*

  V95% [%]

0.0

(−1.4÷1.2)

5.7

(−28.9÷50.0)

0.380

Right temporal lobe

  Dnear-max [Gy(RBE)]

0.6

(−0.2÷2.7)

1.9

(−0.4÷7.9)

0.003*

  Dmean [Gy(RBE)]

2.3

(0.5÷3.0)

15.4

(7.0÷28.7)

<0.001*

  V2% [%]

7.1

(2.4÷16.5)

12.1

(2.5÷38.0)

<0.001*

  V10% [%]

4.5

(1.7÷12.9)

11.5

(2.0÷36.4)

<0.001*

  V60% [%]

2.7

(0.0÷6.9)

20.7

(0.0÷28.2)

0.002*

  V80% [%]

0.6

(−0.0÷2.3)

10.2

(−4.8÷18.3)

0.003*

  V95% [%]

0.0

(−0.8÷2.0)

0.0

(−10.3÷63.9)

0.207

Left hippocampus

  Dnear-max [Gy(RBE)]

0.3

(−0.1÷4.4)

0.7

(−0.3÷76.6)

0.002*

  Dmean [Gy(RBE)]

1.9

(0.3÷5.3)

10.0

(0.8÷81.8)

0.001*

  V2% [%]

0.9

(0.0÷15.0)

0.9

(0.0÷85.4)

0.007*

  V10% [%]

5.8

(0.0 ÷18.5)

6.6

(0.0÷93.6)

0.005*

  V60% [%]

1.7

(−0.2÷12.0)

10.1

(−0.2÷21.7)

0.007*

  V80% [%]

0.7

(0.0 ÷13.1)

9.9

(0.0÷42.8)

0.007*

  V95% [%]

0.0

(−0.3÷5.0)

0.9

(−3.7÷44.7)

0.040*

Right hippocampus

Dnear-max [Gy(RBE)]

0.5

(0.0÷2.3)

1.0

(0.0÷100.0)

<0.001*

  Dmean [Gy(RBE)]

2.5

(0.1÷4.2)

12.9

(4.9÷100.0)

<0.001*

  V2% [%]

1.6

(0.0÷19.4)

2.4

(0.0÷98.1)

0.007*

  V10% [%]

7.1

(0.0÷14.9)

9.5

(0.0÷19.0)

0.007*

  V60% [%]

5.9

(−0.2÷22.1)

15.3

(−184.6÷42.4)

0.004*

  V80% [%]

2.6

(−0.0÷9.1)

11.7

(−16.7÷75.3)

0.004*

  V95% [%]

0.1

(−0.5÷7.5)

0.8

(−14.3÷62.3)

0.118

Left optic nerve

  Dnear-max [Gy(RBE)]

0.1

(−0.9÷3.9)

0.2

(−2.0÷100.0)

0.153

  Dmean [Gy(RBE)]

2.2

(−0.3÷4.0)

11.8

(−0.7÷100.0)

0.004*

  V2% [%]

7.3

(0.0÷17.7)

11.0

(0.0÷59.4)

0.005*

  V10% [%]

8.4

(0.0÷16.8)

13.7

(0.0÷49.1)

0.005*

  V60% [%]

2.0

(0.0÷7.1)

5.9

(0.0÷26.1)

0.003*

  V80% [%]

0.9

(−2.1÷4.7)

2.8

(−41.6÷20.0)

0.042*

  V95% [%]

0.2

(−11.0÷2.1)

2.1

(−42.9 ÷40.6)

0.172

Right optic nerve

Dnear-max [Gy(RBE)]

0.1

(−0.6÷7.3)

0.3

(−1.2 ÷97.8)

0.050

  Dmean [Gy(RBE)]

2.5

(0.0÷5.1)

12.5

(0.0÷100.0)

0.002*

  V2% [%]

10.8

(0.0÷25.7)

14.3

(0.0÷56.7)

0.002*

  V10% [%]

9.0

(0.0÷18.2)

13.2

(0.0÷38.1)

0.003*

  V60% [%]

3.3

(0.0÷7.8)

11.6

(0.0÷48.3)

0.003*

  V80% [%]

1.3

(0.0÷7.1)

8.4

(0.0÷42.4)

0.003*

  V95% [%]

0.2

(−1.2÷3.4)

2.4

(−57.4 ÷52.3)

0.078

  1. Values are median (range) of patient cohort.
  2. Abbreviations: RBE relative biological effectiveness, D near-max , near maximum dose, D mean mean dose, V X% percentage of the volume receiving at least X % of the prescribed dose.
  3. * statistically significant difference (p < 0.05 one-tailed Wilcoxon signed-rank test).