Radiobiology 2016

Direct and Indirect action of radiation in biological systems – X-rays & photons

Indirect Action (70%)

most important for sparsely ionising radiations e.g. X rays (=low LET)

H

OH ·

O

H

Direct Action (30%)

High Doses: OER = 3.0

Low Doses: OER = 2.2

1.0

1.0

0.9

Hypoxic

Hypoxic

0.1

2 nm 4 nm

OER

0.8

0.01

Aerated

Aerated

Surviving fraction

0.7

2.5

0 0.5

1.0

1.5

2.0

3.0

25

10

15

20

30

0

5

Dose (Gy)