501 / 1173
Low Doses: OER = 2.2
0.7
0.9
0.8
1.0
1.5
1.0
2.0
0 0.5
3.0
2.5
Aerated
Hypoxic
High Doses: OER = 3.0
0.1
1.0
5
0
30
10
20
15
25
Aerated
Hypoxic
0.01
OER
2 nm
4 nm
Indirect Action (70%)
OH
·
H
H
O
Direct
and
Indirect
action of radiation in
biological systems – X-rays & photons
Dose (Gy)
Surviving fraction
most important for sparsely ionising
radiations
e.g.
X rays (=low LET)
Direct Action
(30%)