875 / 1544
Lyman model
(1985, Rad Res 104, 13-19)
Basic assumptions
:
•
Dose dependence
: cumulative normal distribution resulting in a sigmoid-shape
dose response curve (error function)/dose-NTCP plane
•
Volume dependence
:
power law relationship
for tolerance doses/dose-volume plane
( )
n
v vD D
*
)1(
50
50
=
(
)
dt
t
NTCP
t
∫
∞−
−
=
2/
exp
2
1
2
π
)( *
)(
50
50
vDm
vDD t
−
=
Parameters
:
D
50
dose to the whole organ giving 50% NTCP
m
steepness (variation in radiosensitivity
across patient population)
n
volume exponent
(volume effect
:
n=1 large,
n=0 small)
(n
descríbes the magnitude of the volume
effect)
extension to non-uniform irradiation
through an algorithm (“DHV reduction”)
LKB model
Parameters for 28 complications:
Burman et al, IJROBP 21, 123 (1991)