Table 3 Mean dose parameters in Gy_E for OARs in 8 NPC patients planned with IMPT and IMRT

Parameter

Mean (Range)

Mean (Range)

Mean dose ratio

Optic chiasm

   D. max

16.1 (0.0 – 52.3)

23.8 (4.8 – 56.8)

0.67

0.008

Spinal cord

   D. max

16.7 (10.1 – 28.7)

46.0 (44.0 – 50.0)

0.36

0.008

Brainstem

   D. max

47.3 (14.6 – 60.5)

58.7 (53.6 – 64.2)

0.80

0.055

Temp. lobe

   D. max

57.2 (33.0 – 67.8)

61.8 (53.5 – 67.7)

0.92

0.021

   D. mean

5.4 (0.5 – 12.3)

13.4 (8.4 – 20.3)

0.40

< 0.0001

Inner ear

   D. max

36.3 (8.0 – 76.1)

51.8 (32.8 – 73.0)

0.70

0.009

   D. mean

13.1 (1.1 – 43.9)

36.4 (21.8 – 53.0)

0.36

< 0.0001

Mid/ext ear

   D. max

37.4 (8.0 – 70.4)

49.2 (33.0 – 68.2)

0.76

0.039

   D. mean

8.1 (0.3 – 13.5)

24.5 (19.4 – 32.8)

0.33

< 0.0001

TM joint

   D. max

54.9 (37.0 – 73.0)

60.5 (45.9 – 71.4)

0.90

0.252

   D. mean

17.4 (7.3 – 28.9)

38.8 (27.9 – 54.6)

0.44

< 0.0001

Larynx/esophgus

   D. max

52.8 (46.6 – 64.4)

57.9 (52.3 – 64.1)

0.91

0.039

   D. mean

14.3 (8.6 – 18.5)

30.6 (24.3 – 35.3)

0.46

0.008

Oral cavity

   D. max

70.2 (68.6 – 73.9)

72.1 (70.4 – 74.4)

0.97

0.055

   D. mean

38.1 (33.9 – 43.7)

44.0 (40.5 – 46.7)

0.86

0.016

Pituitary gl.

   D. max

44.9 (3.2 – 73.0)

53.5 (20.6 – 73.8)

0.84

0.055

   D. mean

34.8 (1.1 – 71.0)

42.2 (11.6 – 65.9)

0.82

0.148

Thyroid gl.

   D. max

51.5 (42.4 – 64.2)

57.5 (52.9 – 64.9)

0.89

0.008

   D. mean

19.8 (12.5 – 24.4)

38.2 (33.7 – 45.4)

0.52

0.008

Parotid gl.

   D. mean

36.3 (23.6 – 44.3)

40.0 (26.0 – 49.0)

0.91

0.011