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ACVR Objectives > Nuclear medicine > Flashcards

Nuclear medicine Flashcards

1
Q

Define activity

A

of radioactive atoms undergoing nuclear transformation per unit time

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2
Q

What is a Curie? (math)

A

Ci = 3.7 x 10^10 disintegrations per second

Amount of distingetrations of 1gm of Radium

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3
Q

What is a Bequerel? (math)

A

1 Bequerel = 1 disintegration per second

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4
Q

How do you convert Curie to Bequerel?

A

1mCi = 37MBq

multiply mCi by 37 to get MBq

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5
Q

What is equation for activity?

A

A = -dN/dt

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6
Q

What is the decay constant?

A

of atoms decaying per unit time is constant and unique to each element.

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7
Q

What is short equation for decay constant?

A

Decay constant = 0.693/ T 1/2 life

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8
Q

How does activity relate to the decay constant (equation)

A

A = λ (decay constant) x N (# of radioactive atoms)

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9
Q

What is the physical half-life?

A

Time required to decrease # of radioactive atoms by 50%

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10
Q

How do you calculate how many radioactive atoms remain after n half-lives?

A 
N = No / 2^n
n = # of half lives that have occurred
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11
Q

What is the decay equation? What other physics equation is it similar too?

A

Nt = No e ^ (λ x t)

Linear attenuation coefficient and the half value layer

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12
Q

What are the 5 types of nuclear transformation?

A

Alpha decay, Positron, Negatron, electron capture, isomeric transition

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13
Q

What occurs in alpha decay?

A

The nuclide will lose 2 neutrons and 2 protons (1 helium atom)

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14
Q

When does Negatron decay occur?

A

In Neutron rich nuclides (high N/Z ratio)

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15
Q

What occurs in negatron decay?

A

Neutron –> Protron (Z+1)
Betatron and anti-neutrino are emitted
Betron acts as an electron - will cause excitation or ionization

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16
Q

When does Positron decay occur?

A

Neutron poor nuclides (low N/Z ratio)

Parent must exceed daughter by energy greater than 1.02 MeV (otherwise electron capture will occur instead)

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17
Q

What occurs in positron decay?

A

Proton –> Neutron (Z-1)
Positron and neutrino are emitted
Positron will interact with anti-particle (Electron) and cause annihilation photons (511keV)

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18
Q

When does electron capture occur?

A

Neutron poor nuclides (Low N/Z ratio)

Will occur in place of positron decay when energy between parent and daughter is less than 1.02 MeV

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19
Q

What occurs in electron capture?

A

Nucleus will capture an orbital electron (K/L shell) –> Proton is converted into neutron (Z-1) –> gamma ray
electron cascade occurs and characteristic radiation occurs

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20
Q

When does isomeric transition occur?

A

When molecules remain in excited (unstable) state for longer than 10^-12s

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21
Q

What occurs in isomeric transition?

A

Metastable –> stable state resulting in production of gamma radiation without changing the mass, proton or neutron number (isobaric and isotonic)

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22
Q

What do the different lines in a decay scheme represent?

A

Horizontal lines (top - parent, middle - excited, bottom - daughter)

Vertical line = gamma ray emission, including isomeric transition

Diagonal (to the left = electron capture, vertical and to the left = positron, to the right = negatron)

23
Q

What is half-life, energy and mode of decay of Technetium 99?

A

Half life - 6 hours
Energy - 140keV
Isomeric transformation

24
Q

What is half-life, energies, and mode of decay of Iodine-131

A

Half life - 8d
Energy - 364 (81%) keV
Decay - Beta negative/Negatron

25
Q

In a feline. What is considered normal thyroid:salivary gland and thyroid:background?

Does this ratio change with time?

A

Thyroid:salivary: 0.8:1
Thyroid:background: 2.75:1

Ratio does not change over time

26
Q

In a dog, what is considered a normal thyroid:salivary gland ratio?

Does this ratio change with time?

A

1:1 - d

This ratio changes after 60 min (will start to decrease)

27
Q

What percentage of feline thyroid hyperplasia are unilateral vs bilateral?

What happens to the other thyroid gland in unilateral cases?

A

Unilateral: 30%
Bilateral: 70%

Other thyroid gland will have reduced uptake - nearly complete

28
Q

What is the most common form of feline thyorid disease?

feline thyroid hyperplasia
feline thyroid adenoma
feline thyroid carcinoma

A

Adenoma

29
Q

What percentage of dogs will have extra-thyroidal tissue?

A

50% - will have around the base of the aorta

30
Q

Where is technetium-99 taken up, and how is it excreted?

A

Taken up: thyroid, salivary gland, GI,

Excretion: mainly renal, but some GI

31
Q

Where is Iodine-131 taken up, and how is it excreted?

A

Taken up: thyroid, salivary glands, stomach, bladder

Excretion: mainly renal, breast tissue, and will cross the placenta

32
Q

What percentages represent each pattern of thyroid uptake in cats?

Unilateral
Bilateral-asymmetric
Bilateral-symmetric
Multifocal

Thyroid scintigraphy findings in 2096 cats with hyperthyroidism. VRU 56.1.

A

Unilateral - 30%
Bilateral asymmetric - 50%
Bilateral symmetric - 10%
Multifocal -

33
Q

What was prevalence of ectopic thyroid tissue and thyroid carcinoma in Thyroid scintigraphy findings in 2096 cats with hyperthyroidism. VRU 56.1.?

A

Ectopic thyroid - 4%

Carcinoma - 2%

34
Q

What was considered a normal thyroid:salivary and thyroid:background in Thyroid scintigraphy findings in 2096 cats with hyperthyroidism. VRU 56.1.?

A

Thyroid:salivary

35
Q

What was sensitivity for thyroid:salivary ratio and thyroid:background in

Thyroid scintigraphy findings in 2096 cats with hyperthyroidism. VRU 56.1.?

A

Thyroid:salivary >1.5 was 0.987

Thyroid:background >6.4 was 0.961

36
Q

What is the difference between physical and biologic half-life?

A

Physical - time it takes for radioactive atoms to decrease by half - sitting in a syringe doing nothing

Biologic - time it takes for radionuclide to lose half of its radiologic activity in the body with interactions with bodily tissues etc

37
Q

What is the effective half life

A

Combination of physical and biologic half-lives

38
Q

How do you calculate the effective half life?

A

T 1/2 effective = (T 1/2 physical x T 1/2 biologic ) (T 1/2 physical + T 1/2 biologic)

39
Q

Describe the line of stability and the chart associated with it?

A

Line of stability is where the N/Z ratio is approximately 1 (neutrons/protons) for low Z elements, and 1.5 for higher elements

Left of the line of stability - Neutron excess –> beta minus decay
Right of the line of stability - proton excess –> positron or electron capture

Further from the line of stability, the more unstable an agent is.

Z > 85 (above bismuth) - are all unstable

40
Q

If a radionuclide is to the left of the line of stability -w hat does this indicate? the right?

A

If to the left of the line of stability will undergo beta-minus decay (neutron rich)
If to the right of the line of stability - will undergo electron capture or positron (proton rich)

Further from the line of stability - more unstable the radionuclide.

41
Q 
What are half lives: 
Tc99
F18
Io131
Co57
A

Tc - 6.0h
F18 - 110min
I131 - 8.0d
Co57 - 271.8d

42
Q

How do you calculate the decay constant?

A

0.693 (which is the natural log of 2) / half life

Label will remain the same!! (Tc will be hr-1, and I will be d-1)

43
Q

What type of decay will occur if the N:Z ratio is high?

A

Negatron decay (beta minus)

44
Q

What type of decay will occur if the N:Z ratio is low?

A

Alpha
Positron
Electron capture

45
Q

Only one form of decay will result in a change in atomic mass… which is it?

A

Alpha decay (A - 4, Z-2)

46
Q

What needs to be present in order for positron decay to occur?

A

1.02MeV of energy for annihilation

47
Q 
Tc99
Z?
Mode of decay
Principle energy
Physical half life
A

43
Isomeric transition
140keV
6 hours

48
Q 
I-131 
Z? 
Mode of decay
Principle nergy
physical half life
A

53
B- (neutron excess) –> Xe-131
364keV
8d

49
Q 
Mo-99
Z? 
Mode of decay
Principle energy
Physical half life
A

42
B- (neutron excess) - Tc-99m
740keV
67h

50
Q 
F-18
Z? 
Mode of decay
principle energu
physical half life
A

9
B+ (neutron poor) - O18
635keV
110min

51
Q 
O-15
Z? 
Mode of decay
principle energu
physical half life
A

8
B+ (neutron poor) - N15
173keV
2 minutes

52
Q

in case we don’t have natural exponential button on our calculators… how can you adjust the decay equation?

A

N = No * 2.78^ (- gamma * t)

53
Q 
Str-89 
Normal A? 
Mode of decay
principle energu
physical half life
A

38
Beta - Yttrium 89
None
50d

54
Q 
I-123
Normal A? 
Mode of decay
principle energu
physical half life
A

53
Electron capture
159keV
13.2h

ACVR Objectives (18 decks)

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