BCRB 2018

Direct and Indirect action of radiation in biological systems

Indirect Action

most important for sparsely ionising radiations e.g. X rays

Direct Action OH · H H

O

High Doses: OER = 3.0 15 MeV Neutrons

Low Doses: OER = 2.2 a particles

1.0 1.0

1.0

1.0

OER = 1.0

OER = 1.6

0.9 0.1

0.1

Hypoxic

Hypoxic

0.1

2 nm 4 nm

Hypoxic

OER

Aerated

0.8 0.01

0.01

Hypoxic

0.01

Aerated

Aerated

Aerated

0.7 0.001

5 0 Surviving fraction 0 2 0.001 10

0 0.5

1.0

1.5

2.0

2.5

3.0

25

15

20

30

1.0

2.0

3.0

6

4

Dose (Gy)