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physics clinical imaging > Ionising Radiation > Flashcards

Ionising Radiation Flashcards

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1
Q

What are the characteristics of ionising radiation

A

Penetrating
Invisible to the eye
Can cause tissue damage

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2
Q

What are examples of natural radiation

A

Cosmic, animals, buildings, food, people, radon gas

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3
Q

What are examples of artificial radiation

A

Medical imaging, nuclear power, missiles and nuclear weapon testing

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4
Q

What is a half value layer

A

The thickness of a substance which will transmit one half of the intensity of radiation incident upon it

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5
Q

What is a half life

A

Time taken for half of the atoms to decay

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6
Q

True or false - you can predict when an individual atom will decay

A

False - it is impossible as radioactive decay is a random process

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7
Q

What are we able to predict involved with half lives

A

The fraction of the atoms that will decay over a period of time

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8
Q

What is the inverse square law

A

The concentration of radiation is inversely proportional to the square of the distance - intensity reduces with distance

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9
Q

What are the 3 practical principles of radiation safety

A

Time distance shielding

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10
Q

What is the lead equivalence

A

The lead equivalent of an absorbing material is the thickness of lead which would absorb the same amount of radiation as the given material when exposed to radiation of the same type

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11
Q

What is radon gas

A

Chemical element with the atomic number of 86 - it is a radioactive colourless and tastelesss gas

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12
Q

How is radon gas formed

A

Radioactive decay of small amounts of uranium that occur naturally in rocks and soils

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13
Q

What is the banana equivalent dose

A

Informal way of comparing doses of radiation to the dose received by eating a single banana

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14
Q

What is radioactive decay

A

Process of an unstable atomic nucleus loses energy by emitting radiation such as alpha beta or gamma particle

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15
Q

What is alpha decay

A

Spontaneous emission of an alpha particle from a nucleus

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16
Q

What does alpha radiation consist of

A

Two protons and neutrons tightly bound together - a helium nucleus

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17
Q

What is beta decay

A

Spontaneous emission of a fast moving particle with the mass of an electron from a nucleus

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18
Q

What type of particles are produced by beta decay

A

Both negative and positive

19
Q

What is gamma decay

A

Spontaneous emission of a high energy photon with no mass from the nucleus

20
Q

Which type of radiation consists of helium-4

A

Alpha

21
Q

Which type of decay can be stopped by a aluminium plate

A

Beta

22
Q

What does beta radiation consist of

A

High energy protons or electrons

23
Q

What can stop alpha radiation

A

Sheet of paper

24
Q

What can stop gamma radiation

A

Lead

25
Q

What are the 2 classifications of action / damage resulting from radiation of cells

A

Direct and indirect

26
Q

What is indirect action / damage to tissue

A

Free radicals a produced by ionisation of water

27
Q

What is direction action / damage to tissue

A

Ionisation of macromolecules such as DNA, enzymes and proteins

28
Q

Which is the most destructive radiation

A

Alpha

29
Q

What happens in beta minus decay

A

Neutron decays to a proton and releases an electron

30
Q

What happens in beta plus decay

A

A proton decays to a neutron and releases a positron

31
Q

What is a positron

A

A positively charged electron

32
Q

How do free radicals work in indirect tissue damage

A

By transferring excess energy to other molecules and breaking chemical bonds

33
Q

What can free radicals in indirect tissue damage produce

A

Hydrogen peroxide and hydroperoxyl radical which are both highly reactive and can cause biological damage

34
Q

What are chromosomal effects from direct damage

A

Abnormal replication, cell death and the inability to pass on info

35
Q

What is the linear energy transfer

A

How much energy is transferred per unit length

36
Q

What are the two main categories of biological effects of radiation

A

Deterministic effects (tissue reactions)
Stochastic effects

37
Q

What are deterministic effects - tissue reaction

A

Non cancer damaging effects that wiki definitely result from high dose radiation

38
Q

What are stochastic effects cancer and genetic effects that may develop

A
39
Q

What is the relationship between the severity of the effect and the threshold dose

A

Directionally - as one increases so does the other

40
Q

What are the subdivisions of tissue reactions

A

Early and late

41
Q

The ICRP uses which model

A

Liner non threshold model

42
Q

What is absorbed dose

A

Energy deposited per unit mass as is measured in joules per kg

43
Q

What symbol is used for absorbed dose

A

Gy - gray

44
Q

True or false Gy is a SI unit

A

True

physics clinical imaging (6 decks)

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