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P3 topic 3 Flashcards

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1
Q

what are the side effects of palliative radiotherapy?

A

tiredness, sickness, feeling very sore

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2
Q

when does palliative radiotherapy cause sickness?

A

if there has been treatment to the stomach, abdomen or brain

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3
Q

when does palliative radiotherapy cause the patient to feel sore?

A

following treatment to the lung, head or neck

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4
Q

what are patients often prescribed to control sickness?

A

they are often prescribed anti-emetic drugs

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5
Q

what’s a problem with radiotherapy?

A

not all cancers respond well to it

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6
Q

why does radiotherapy cause damage to cells?

A

the radiation ionises the atoms in the cells

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7
Q

What does external radiotherapy work well for?

A

treating cancer cells in a localised area of the body

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8
Q

what is a benefit of external radiotherapy?

A

patients can have external radiotherapy for more than one area of the body at the same time

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9
Q

how regularly can patients have external radiotherapy?

A

patients can have 1 or 2 treatments or up to 10 short treatments given over 2 weeks

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10
Q

what are the different types of internal radiotherapy?

A

an injection, a radioactive metal implant inserted into the patient’s body, drink or capsule containing radioactive materials

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11
Q

what are injections of radioactive substances usually used for?

A

to treat widespread cancer in the bones

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12
Q

where is the radioactive metal implant put inside the body?

A

very close to the cancer- these are sometimes in the form of wires

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13
Q

what are patients told after being treated with radioactive materials?

A

they are often allowed to go home, but to to steer clear of children or pregnant women

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14
Q

what can also be used in the

treatment of cancer?

A

an intense beam of fast moving neutrons

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15
Q

how can neutrons ionise atoms?

A

they have no charge, but because they have a large speed and mass they have enormous amounts of kinetic energy and can ionise atoms- they can produce 5 times more ionisation than x rays and beta particles

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16
Q

how are intense neutrons beams produced?

A

by bombarding berylium with protons from a particle accelerator

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17
Q

how is the neutron beam used?

A

it’s pointed at the tumour with the help of lasers and is able to stop the growth of the tumour or possibly destroy it completely

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18
Q

palliative radiotherapy

A

treatment to shrink a cancer or slow down its growth- it doesn’t aim to cure the cancer completely and uses either external or internal radiation

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19
Q

medical radioactive tracer

A

a radioactive substance that is either injected into or swallowed by a patient

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20
Q

tracers

A

they are absorbed differently by different tissues in the body; a radiation detecter can produced an image showing the distribution of the radioactive substance

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21
Q

what are radioactive tracers?

A

either beta or gamma emitters with short half lives

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22
Q

Iodine-131

A

beta; half life of 8.1 days; used to monitor passage of fluid through the kidney

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23
Q

Technetium-99

A

gamma; half life of 6 hours; used to monitor blood flow in the brain or lungs, growth of bones; blood circulation in the heart

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24
Q

Xenon-133

A

gamma; half life of 2.3 days; used to monitor the function of the lungs

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25
Q

how does iodine-131 work?

A

a healthy kidney will pass the iodine through to the bladder; if there is a blockage, the iodine builds up in the kidney and can be detected

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26
Q

why does the radioactive tracer need to have a suitable half-life?

A

it can’t be so short that there is no time to see the effect, but it can’t be too long so the tracer does not exist for too long in the body

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27
Q

what are PET scanners used to monitor?

A

activity of the brain; spread of cancer through the body; flow of blood through organs such as the heart

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28
Q

what are radioactive isotopes (beta-plus emitters) first produced in?

A

a cyclotron

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29
Q

radiopharmaceutical

A

a substance produced by tagging radioactive isotopes to natural chemicals in the body such as glucose, ammonia and water- it’s injected into the patient

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30
Q

what will happen when the radiopharmaceutical is injected into the body?

A

it will go to areas which use the natural chemical

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31
Q

what is fluorine-18 tagged to?

A

glucose to produce fluorodeoxyglucose (FDG)- cancers use glucose differently from normal tissues so the FDG will reveal cancerous tissues

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32
Q

what do the radioactive isotopes used include?

A

carbon-11, nitrogen-13, oxygen-15 and fluorine-18 which have short half lives

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33
Q

what does a PET detect to work?

A

the gamma rays produced by the annihilation of positrons (emitted by radioactive isotopes) and electrons

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34
Q

why are PET scanners very expensive?

A

they also require a cyclotron to produce the radiopharmaceuticals

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35
Q

how many PET scanners are there around the world?

A

only about 150- mostly in the developed world- USA, Europe and Japan

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36
Q

what can ionising radiation do?

A

damage body tissue- cells may mutate, die or fail to reproduce themselves

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37
Q

effects of radiation damage

A

skin burns, nausea, destruction of bone marrow, hair loss, sterility, cancers, changes to genetic material

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38
Q

how are people who work with ionising radiation protected?

A

keeping the distance between workers and source of radiation as large as possible, keeping exposure time to a min, using shielding such as lead-lined aprons or concrete walls; wearing dosimeters

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39
Q

dosimeters

A

radiation-sensitive film within a holder- the film goes darker when exposed to increasing amounts of radiation

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40
Q

what are the three types of damage causes to cells by ionising radiation?

A

cells become damaged then repair themselves and operate normally; cells become damaged then repair themselves but function abnormally, such as failing to reproduce themselves or reproducing at an uncontrolled rate- this is the main cause of cancers; cells become so damaged they die

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41
Q

what does the amount of damage caused by the radiation depend on?

A

the dose received; the parts of the body exposed; the nature of the radiation- alpha particles are easily stopped by the skin, so do not present a serious problem until the source gets inside the body

42
Q

which parts of the body are most susceptible to radiation?

A

rapidly dividing cells (such as blood cells and hair follicles)

43
Q

equivalent dose

A

the effective biological damage to human tissue by ionising radiation is known as the equivalent dose

44
Q

what is the equivalent dose measured in?

A

Sieverts (Sv)

45
Q

what happens the higher the equivalent dose?

A

the greater the chance of biological damage

46
Q

what’s the max radiation dose a day that causes no actuate symptoms?

A

up to 0.25 Sv a day

47
Q

when does the radiation dose begin to cause acute symptoms?

A

between 0.25 Sv and 1 Sv a day can cause nausea, loss of appetite and damage to bone marrow

48
Q

what is the maximum permissible dose for medical personnel a year?

A

20 mSv per year, averaged over 5 years, with a max of 50 mSv in any one year

49
Q

what are patients always given?

A

the smallest dose of radiation needed for their treatment

50
Q

equivalent dose of dental x ray

A

0.0005 mSv

51
Q

equivalent dose of full body CAT scan

A

15 mSv

52
Q

equivalent dose of fluoroscopy

A

5 mSv

53
Q

estimated max dose to residents of Fukushima following nuclear accident in 2011

A

68 mSv

54
Q

quarks

A

tiny particles which make up all matter

55
Q

who was the quark model proposed by?

A

independently by both Murray Gell-Mann and George Zweig in 1964

56
Q

what are quarks?

A

fundamental particles- they cannot be subdivided into smaller particles

57
Q

fundamental particles

A

electrons, positrons and quarks

58
Q

charge of up quark

A

+ two thirds e

59
Q

charge of down quark

A

-a third e

60
Q

what do both experiment and theory show?

A

that it’s impossible to isolate quarks

61
Q

what are the quarks that make up a neutron?

A

one up quark and two down quarks

62
Q

what are the quarks that make up a proton?

A

two up quarks and one down quark

63
Q

how big is a quark compared to a proton or a neutron?

A

80 times smaller

64
Q

beta minus decay and quarks

A

a down quark in a neutron changes into an up quark and an electron, the electron is emitted as a beta-minus particle so the neutron now has two up quarks and one down quark, so is now a proton

65
Q

beta plus decay and quarks

A

an up quark in a proton changes into a down quark and a positron; the positron is emitted as a beta-plus particle so the proton now has 2 down quarks and one up quark so is now a neutron

66
Q

how might a proton in the nucleus change?

A

through beta-plus decay into a neutron and a positron

67
Q

what can happen to a neutron on its own?

A

it can decay to release an electron- the half-life of a free neutron is about 11 minutes

68
Q

N-Z curve

A

a graph if the number of neutrons against the number of protons for all known nuclei

69
Q

where do the stable nuclei lie?

A

on a curve starting from the origin with slightly increasing gradient (black line on graph)

70
Q

what do stable nuclei with atomic numbers less than 20 have?

A

equal numbers of neutrons and protons

71
Q

what do most stable nuclei have?

A

more neutrons than protons

72
Q

what are unstable nuclei above the stability curve?

A

neutron rich- those below are neutron poor

73
Q

what are the protons and the neutrons in the nucleus held together by?

A

a strong nuclear force, which has to overcome the repulsion between the positively charged protons

74
Q

how does a neutron rich nucleus decay?

A

it has too many neutrons to be stable and decays by emitting a beta-minus (electron)- a neutron changes into a proton and an electron- this brings the nucleus closer to the stability curve

75
Q

how does a neutron poor nucleus decay?

A

it has too many protons to be stable and decays by emitting a beta-plus (positron)- a proton changes into a neutron and a positron- this brings the nucleus closer to the stability curve

76
Q

what decays by emitting alpha particles?

A

unstable nuclei with a high atomic number (above 82) decay by emitting alpha particles- this has little effect on the nucleus’ position relative to the stability curve

77
Q

what also happens during beta plus decay?

A

a nucleus also emits a neutrino- neutrinos have no charge and a negligible mass, so they don’t interact with matter and are therefore very difficult to detect

78
Q

what is the mass of a neutrino?

A

one billionth of the mass of a proton

79
Q

when was the existence of neutrinos predicted?

A

by Wolfgang Pauli in 1930, but they are only discovered 26 years later

80
Q

what links the universe and neutrinos?

A

the universe is believed to be saturated with neutrinos

81
Q

what does an alpha particle contain?

A

2 protons and 2 neutrons

82
Q

what may an unstable nucleus of heavier atoms do?

A

emit alpha particles and transmute into a new daughter nucleus

83
Q

what do done lighter nuclei do?

A

emit beta particles which are fast moving electrons

84
Q

what happens in beta minus decay?

A

a neutron inside the nucleus changes into a proton and an electron; the electron is emitted as a beta particle and the proton remains in the nucleus

85
Q

gamma decay

A

gamma rays are often emitted following alpha or beta emission to reduce surplus energy; gamma rays have no charge and so there is no change to the structure of the nucleus- the nucleus undergoes some rearrangement to get to a lower energy state

86
Q

what type of decay do some proton rich nuclei undergo?

A

positron (beta plus decay)

87
Q

beta plus decay

A

a positron removes a positive charge from the nucleus- a proton changes into a positron

88
Q

what are all materials made up of?

A

atoms

89
Q

isotopes

A

nuclei which have the same number of protons, but differing numbers of neutrons

90
Q

mass of an electron

A

0.00055

91
Q

what do some heavier isotopes emit to become stable?

A

neutrons

92
Q

positron

A

the same mass as an electron but it has a positive charge of 1.6 X 10 -19- it’s the antiparticle to an electron

93
Q

alpha

A

helium nucleus; 2+ charge; strongly ionising; stopped by paper, skin or 6cm air

94
Q

beta

A

electron; 1-; weakly ionising, stopped by a few mm of aluminium

95
Q

gamma

A

short wavelength EM radiation; no charge; very weakly ionising, significantly absorbed by a few cm of lead, or a few m of concrete

96
Q

neutron

A

no charge; does not interacting with matter

97
Q

beta-plus

A

positron; 1+; a positron interacts strongly with an electron to produce gamma rays

98
Q

what are radioactive materials used in?

A

the treatment and diagnosis of cancer

99
Q

what can ionising radiations do?

A

damage living cells, so exposure is kept to a minimum

100
Q

what do radiographers and other people who work with ionising radiation need to do?

A

wear protective clothing, usually made of lead- they also wear dosimeters to record the amount of radiation exposure

Physics (15 decks)

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