Table 1.

Normal‐tissue tolerance parameters for calculation of normal‐tissue complication probability

Organ at risk	$T{D}_{50}$(1) (Gy)	n	m
Brainstem	65	0.16	0.14
Brain–PTV	60	0.25	0.15
Optic nerves	65	0.25	0.14
Optic chiasm	65	0.25	0.14
Cochlea	60	0.25	0.15

$T{D}_{50}(1)=$ tolerance dose to the organ; $n=\text{volume}\hspace{0.17em}\text{effect}$; $m=$ slope of the dose–response curve; $\text{PTV}=\text{planning}\hspace{0.17em}\text{tumor}\hspace{0.17em}\text{volume}$.