RBP L1 - Interactions of Radiation

Question 1

What is “Radiobiology”? What is its aim?

Answer 1

Radiobiology is the study of the effect of ionising radiation on living things. The aim is to know their effects/how to prevent it/protection from it etc…

Question 2

How much energy is given per ionising event? How many DNA strands can this break?

Answer 2

33eV; each DNA strand is about 5eV, so can break 6 DNA strands

Question 3

How fast do Photons travel?

Answer 3

3 x 10^8 m/s

Question 4

What are the two types of ionising radiation? How are their properties different?

Answer 4

Two types: electromagnetic (comes from light waves), and particulate (comes from particles i.e. alpha, beta)

Question 5

What is the relationship between x-rays and gamma rays?

Answer 5

x-rays are produced extranuclearly (acceleration of electrons), gamma rays are produced intranuclearly (from nucleus decaying and giving off energy)

Question 6

Is electromagnetic radiation direct or indirect ionising? What about particulate?

Answer 6

INDIRECT (electromag), DIRECT (particulate)

Question 7

Compare alpha and beta particles - number of ionisations, length travelled in air and in soft tissue

Answer 7

alpha: 40k atoms/cm ionised, 5cm in air, <100microm in soft
beta: hundreds/cm ionised, transverses 10-100cm air, 1-3cm soft tissue

Question 8

electromagnetic radiations are usually considered ionising if they have a photon energy in excess of ___eV

Answer 8

124eV

Question 9

What is the diff between direct/indirect action of radiation; Explain using Compton

Answer 9

They BOTH undergo Compton effect - What happens after this is what differentiates direct and indirect.
Indirect: ejected e- goes and hits water, free radical produced, which then goes and damages DNA
Direct: ejected e- goes directly to DNA and damages it

Question 10

Know how to do calculations: absorbed dose, equivalent dose, effective dose…

Answer 10

.

Question 11

Equivalent dose is a measure of the biological effect of radiation

Answer 11

True

Question 12

Energy deposition per unit mass in any medium by any type of ionising radiation is called absorbed dose.

Answer 12

True

Question 13

Effective Dose indicates the effects of radiation on the body as a whole when different body tissues are exposed to different levels of equivalent dose.

Answer 13

True

Question 14

Effective dose is obtained by summing all the equivalent doses to all of the tissues and organs of the body, multiplied by a weighting factor for each tissue or organ.

Answer 14

True

Question 15

The response of tissue to radiation is principally a function of which of?

Answer 15

DOSE

Question 16

How much energy per ionising event?

Answer 16

33eV

Question 17

How much energy neeeded to break a DNa bond?

Answer 17

5eV

Question 18

Where are gamma and x-rays sourced?

Answer 18

gamma: nuclear actions/radioactive isotopes, x rays are sourced from electron clouds

Question 19

Alpha particles in air? Soft tissue?

Answer 19

5cm, 100microm

Question 20

Beta particles in air? Soft tissue?

Answer 20

10-100cm in air, 1-3cm in soft tissue

Question 21

How much atoms does alpha particulate ionising /cm in air?

Answer 21

40,000

Question 22

What is absorbed dose measured in? What is this equivalent to?

Answer 22

1Gy, which is 1J/kg

Question 23

What is effective and equivalent dose measured in?

Answer 23

Sv