Energy

6 MV

6 FFF

15 MV

6 MeV

9 MeV

12 MeV

ρ

−0.231

−0.445

−0.331

−0.379

−0.416

−0.178

n

29

21

26

24

24

27

p-value

0.229

0.043

0.098

0.068

0.043

0.375