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Medical Radiation Sciences 2 > Radioactivity > Flashcards

Radioactivity Flashcards

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USMLE® Step 1 flashcards
1
Q

What is atomic number?

A

Z/number of protons

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2
Q

What is atomic mass?

A

A/Number of nucleons

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3
Q

What is the symbol for neutrons?

A

n

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4
Q

What affects how stable an atom is?

A

The number of neutrons to protons

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5
Q

Why does the atom need neutrons?

A

Without neutrons, the protons would repel each other

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6
Q

What is the force that holds the nucelus together?

A

Nuclear force

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7
Q

With more protons present, would we need more or less neutrons?

A

More neutrons

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8
Q

T/F

The first 20 elements have a 1:3 ratio of neutrons to protons.

A

False; the first 20 elements have a 1:1 ratio

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9
Q

T/F

In nuclei with the atomic number greater than 20, the number of neutrons exceeds the number of protons.

A

True

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10
Q

What is decay?

A

The release of a particle that could cause damage

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11
Q

What is the purpose of radioactivity?

A

To achieve the ideal balance of neutrons and protons through disintegration

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12
Q

Is it possible to control the rate of radioactive breakdown of a nucleide?

A

No

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13
Q

What type of nucleide is created from a parent radionuclide disintegrating?

A

Daughter product

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14
Q

What is an isotope?

A

An atom with the same number of protons but a different number of neutrons

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15
Q

T/F

A radioisotope can be natural or man-made.

A

True

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16
Q

What element is the last stable element?

A

83 (bismuth)

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17
Q

How many protons at minumum do elements need to have to be conisdered radioactive?

A

84 protons at minumum

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18
Q

T/F

Everything about an atomic number of 83 cannot exist in a stable state, so they will decay.

A

True

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19
Q

What is the neutron to proton ratio for elements with an atomic number of 1-20?

A

1

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20
Q

What is the neutron to proton ratio for elements with an atomic number of 20-40

A

1.25

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21
Q

What is the neutron to proton ratio for elements with an atomic number of 40-83?

A

1.5

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22
Q

T/F

In a nuclear reaction all the protons and neutrons in a nucleus must be accounted for on both sides of the reaction.

A

True

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23
Q

What do each of these letter stand for in the following equation?:
X–> R + Y

A

X=Reactants
R+Y=Products

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24
Q

What are the 3 different types of radioactive decay?

A
  1. Alpha decay
  2. Beta decay
  3. Gamma decay
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25
Q

What does the type of radioactive decay depend on?

A

How its neutron to proton ratio compares with those elements of a nearby nucli that lie within the belt of stability

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26
Q

T/F

Alpha paricle are light.

A

False; heavy nuclei

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27
Q

What is the problem with the nuclei that leads to alpha decay?

A

The nucleus is too large to balance forces
(the atomic mass is too high)

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28
Q

What is an alpha particle made up of?

A

2 protons and 2 neutrons

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29
Q

What is an alpha particle identical in mass and number to?

A

Helium

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30
Q

What reaction has occured here?

A

Alpha decay

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31
Q

How does alpha decay solve the issue with unstable elements?

A

The release of alpha particles decrease atomic mass, solving the issue of heavy unstable elements

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32
Q

What direction does the nucleus move towards the belt of stability?

A

To the left and diagonally towards the belt of stability

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33
Q

What is the charge of an alpha particle?

A

Positive

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34
Q

T/F

Alpha particles are very ionizing.

A

True

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35
Q

How far can an alpha particle travel in air and soft tissue?

A

Air: 1-10 cm
Soft tissue: .1mm

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36
Q

T/F

Beta- particles are have neutron rich nuclei.

A

True

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37
Q

What is the problem with the elements that result in beta negative decay?

A

There are too many neutrons (the n:p ratio is too high)

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38
Q

T/F

In beta negative decay, the mass will not change

A

True

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39
Q

What is the mass of a beta particle?

A

0

40
Q

How do you know that alpha decay will take place?

A

If the atomic number is over 80

41
Q

What is the solution for Beta particle (𝛽-) emission to get back to the nuclear belt of stability?

A

Decrease the number of neutrons by one, and increase the number of protons by one

42
Q

What is the end product?

A

137Ba
56

43
Q

Which way does the decay scheme go for beta negative decay?

A

Down and to the right

44
Q

T/F

A beta negative particle has the same mass and charge as an electron.

A

True

45
Q

What is the range of penetration for beta negative particles?

A

3mm in soft tissue

46
Q

T/F

Beta positive particles have proton rich nuclei

A

True

47
Q

What is the issue with the unstability of beta positive particles?

A

-Too many protons
-n:p too low

48
Q

What is the symbol for beta positive decay?

A
49
Q

What is the solution for unstable beta positive particles?

A

-Reduce atomic number or increase the number of neutrons

50
Q

What is the end product?

A

15N
7

51
Q

What happends to beta positive particles after they decay?

A

They combine with negative electrons and disappear in annihalation radiation

52
Q

Write out the radioactive decay reaction for:

238U(92)
A

238U(92)—>4a(2)=234Th(90)

53
Q
  1. Is it stable or radioactive
  2. What type of emmission would it give off?
  3. Write out the nuclear reaction formula
A
  1. Radioactive
  2. Beta negative
  3. 0B(-1)=90Ga(31)
54
Q
  1. Is it stable or radioactive
  2. What type of emmission would it give off?
  3. Write out the nuclear reaction formula
A
  1. Radioactive
  2. Beta positive
  3. 0B(+1)=100Pr(59)
55
Q
  1. Is it stable or radioactive
  2. What type of emmission would it give off?
  3. Write out the nuclear reaction formula
A
  1. Stable
  2. None
  3. None
56
Q

If the n:z ratio is too high, what is likely to occur?

A

Neutrons are converted to protons via beta decay

57
Q

If the n:z ratio is too low, what is likely to occur?

A

Protons are converted to neutrons via positiron emission

58
Q

If amu is too high what is likely to occur?

A

A change to both nuetrons and protons through alpha decay

59
Q

What process is this describing

A nuclear processes in which a nucleus with excess E following alpha or beta particle emission, emits E without chaning number of protons or neutrons.

A

Isomeric Reaction

60
Q

T/F

The exitied nuclear state following the emission of a beta or alpha particle may be nearly stable.

A

True

61
Q

T/F

Gamma emission decay processes often leave the daughter nucleus in an excited state.

A

True

62
Q

T/F

No numbers change in gamma decay.

A

True

63
Q

What does metastable mean?

A

Too much energy

64
Q

What is the symbol for gamma radiation?

A

0y
0

65
Q

T/F

Gamma radiation emission affects the n:z ratio

A

False; Does not affect the n:z ratio.

66
Q

What is the charge and mass of a gamma particle?

A

Zero

67
Q

How much soft tissue can a gamma particle penetrate?

A

30cm in soft tissue

68
Q

What radionuclide is used in radiotherapy?

A

60CO
27

69
Q

What is absorbed dose?

A

Absorbed dose is a measure of the energy absorbed per unit mass of tissue

70
Q

What is LET

A

Average (radiation) energy deposited per unit path length along the track of an ionizing particle

71
Q

What are the units for LET?

A

keV/μm

72
Q

What does LET depend on?

A
  1. the nature of the radiation
  2. material traversed
73
Q

T/F

A high LET will attenuate the beam/particle more quickly

A

True

74
Q

What are 3 examples of high LET radiation?

A
  1. α-particles
  2. protons
  3. neutrons
75
Q

Is this high or low LET?

3 – 200 keV/µm

A

High LET

76
Q

What are 4 examples of low LET radiaton?

A
  1. Electrons
  2. positrons
  3. gamma rays
  4. x-rays
77
Q

Is this high or low LET radiation?

0.2 – 3 keV/µm

A

Low LET radiation

78
Q

What is the radioactive half life? What is it denoted by?

A

-Time that is required for one half of the sample to decay
-T1/2

79
Q

If you start off with 50g of Cs, which has a HL of 14 years, how much Cs will be present 42 years later?

A

6.25 gm

Ask

80
Q

What is radioactive activty? What is it denoted as?

A

-Number of radioactive decays per second
-A

81
Q

What is the SI Unit for radioactivity?

A

Becquerel (Bq)

82
Q

T/F

Bq is defined as an activity of one transformation/decay per second

A

True

83
Q

T/F

1 Bq = 10/s

A

False; 1 Bq = 1/s

84
Q

What does radoactive activity depend on?

A
  1. Amount of the substance
  2. Half life
85
Q

Will a higher mass of a radioactive substance produce more or less activity?

A

More activity

86
Q

What is the relationship between mass and activity?

A

Directly proportional

87
Q

Will a long half life have more or less activity?

A

Less activity

88
Q

What is the relationship between half life and activity?

A

Indirectly proportional

89
Q

What is the Decay constant (⋋)?

A

The number of atoms of the radionuclide breaking down per unit time (per second)

90
Q

If the total number of atoms in a radionuclide is 5000000, and the number of atoms breaking down per second is 50000, then what is the decay constant (⋋)?

A

⋋ = 50000/5000000 = 0.01 = 10^-2/s

91
Q

T/F

Half life and decay rate are constant.

A

True

92
Q

What is the relationship between half life and decay rate?

A

They are inversely proportional to eachother.

The shorter the half life, the faster/larger the decay

93
Q

What are the two uses for radioactive activity in medical imaging?

A
  1. Theraputic reasons
  2. Diagnostic reasons
94
Q

What are the 3 studies done with radioactive activity for diagnostic purposes?

A
  1. Physiological studies
  2. Blood volume studies
  3. Imaging studies
95
Q

What are blood volume studies done with radioactive materials?

A

Total volume of blood can be estimated by measuring its diluting effect on a known amount of radionuclide

96
Q

Pictures for understanding

A

Medical Radiation Sciences 2 (13 decks)

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