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ABR Nuc Med > Radiation and Radionuclides > Flashcards

Radiation and Radionuclides Flashcards

1
Q

Typical distance traveled by an alpha particle (4-8 MeV) in tissue

A

.03 mm

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2
Q

Amount the mass number (A) decreases in alpha decay

A

4

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3
Q

Designated by “A”, refers to the number of protons plus neutrons

A

Mass Number

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4
Q

Designated by “Z”, refers to the number of protons

A

Atomic Number

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5
Q

The atomic number above which K shell electrons have an energy > 25 KeV (useful for imaging)

A

50

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6
Q

Electron capture is sometimes called the inverse of

A

β- decay

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7
Q

The force keeps the nucleus bound

A

Strong Nuclear Force

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8
Q

Transition energy required for β+ decay

A

1.022 MeV

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9
Q

True or False, transitions from any electron orbital shell to any other orbital shell are allowed

A

False, some transitions are not allowed due to selection rules of quantum mechanics

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10
Q

The average β- energy is

A

1/3 E Beta Max

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11
Q

c = ?

A

c = λν

(wavelenth × frequency)

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12
Q

Name two isotopes that decay solely by β- decay

A

3H

14C

32P

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13
Q

Internal conversion

A

Energy is transferred directly to an inner shell electron, which is ejected from the atom.

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14
Q

In this decay chart, the atomic number does what?

A

Atomic number is increasing, going to 14N

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15
Q

This chart illustrates what type of decay?

A

Isomeric Transition

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16
Q

An alternative to γ emission

A

Internal conversion

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17
Q

True or False

There can be subtle differences in chemical behavior based on varying isotope mass, e.g., 3H

A

True

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18
Q

Internal conversion and electron capture can be very slightly altered by the chemical environment

A

True

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19
Q

β- decay produces this massless particle

A

Anti neutrino

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20
Q

β+ decay produces this massless particle

A

Neutrino

ν

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21
Q

Two medically relevant isotopes that undergo β- decay are

A

131I

137Cs

133Xe

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22
Q

A medically relevant isotope that undergoes isomeric transition

A

99mTc

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23
Q

This graph illustrates what type of decay

A

Internal conversion

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24
Q

2 forms of radiation following internal conversion

A

characteristic x-rays

auger electrons

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25
Q

True or False

As compared to β- decay, electrons from internal conversion have a discrete series of energies.

A

True

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26
Q

The most popular radionuclide for nuclear imaging studies.

A

99mTc

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27
Q

Medically important radionuclides that decay via (EC,γ)

A

57Co

67Ga

111In

123I

125I

201Tl

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28
Q

In electron capture, Z

A

decreases

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29
Q

True or False

The K-xrays of lighter elements and all L-xrays are of lower energy and not suitable for external measurments.

A

True

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30
Q

Sometimes called inverse beta decay

A

Electron Capture

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31
Q

Average β+ energy

A

1/3 E β+, Max

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32
Q

In β+ decay, Z ___________

A

decreases

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33
Q

Medically important β+ radionuclides include

A

18F

15O

13N

11C

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34
Q

EC tends to occur in _________elements while β+ occurs more frequently in __________elements

A

heavier

lighter

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35
Q

Fraction of 18F decaying by β+

A

97%

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36
Q

True or False

Odd-odd nuclei tend to be more stable than even-even nuclei

A

False

Even-even nuclei are relatively stable because of pairing of alike particles within the nucleus.

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37
Q

For a giving decay mode, the branching ratio (B.R.) for the ith decay mode is given by

A

B.R. = λi / λ

38
Q

For a nuclei with multiple decay paths, the decay constant =

A

λ = λ1 + λ2 + λ3 + …

39
Q

Given the half-life of an isotope, the decay constant can be calculated as

A

λ = ln(2) / t½

or

.693 / t½

40
Q

1 Ci = ____________dps (Bq)

A

3.7 E10

41
Q

1 mCi = _______________MBq

A

37

42
Q

The average half-life of a radionuclide =

A

τ = 1 / λ

or

1.44 t½

43
Q

Image frame decay corrections may be needed when the imaging time is ____________ relative to the half-life of the isotope.

A

long

e.g., F-18

44
Q

The effective decay factor for image count correction can be calculated as

A

DFeff (t, Δt) ≈DF[t + Δt/2]

accurate to within 1% for

x<0.5 where x = ln(2) × Δt/T½

45
Q

The specific activity (Bq/g) of an isotope can be calculated as

A

Bq/g = λ × 6.023E23 / GAW

GAW ≈ gram atomic weight [g/mol]

46
Q

The highest specific activity of a radionuclide is its ___________

A

CFSA

carrier-free specific activity

47
Q

For a mixture of radioisotopes, the total activity =

A

A = A1 + A2 + A3 + …

48
Q

The Bateman equation describes _________________ relationships.

A

parent-daughter

49
Q

The Bateman equation is given by

_________________________

and describes the activity of the ________________ as a function of time

A

daughter

50
Q

In secular equilibrium, the relationship of the parent daughter half-lives is

A

λd>>λp

or

Td << Tp

51
Q

In secular equilibrium the Bateman equation simplifies to

A
52
Q

This graph illustrates

A

Secular equilibrium

53
Q

An example of medically relevant transient equilibrium is

A

99Mo (T½ = 66 hr) ⇒ 99mTc (T½ = 6 hr)

54
Q

This figure represents

A

Transient equilibrium

55
Q

For a radionuclide approaching secular equilibrium with a branching ratio of 1, the daughter activity at 1 and 2 daughter half-lives can be estimated as _____________, _______________. The activity of the daughter will effectively equal the activity of the parent after about ___________ .

A

Ad = (1/2) Ap

Ad = (3/4) Ap

5 Td

56
Q

In transient equilibrium, the ratio of daughter to parent is

A

Ad / Ap = [Tp/ (Tp - Td)] × B.R.

Remember in transient equilibrium Tp > Td so to keep things positive the equation must be Tp - Td

57
Q

In transient equilibrium, the maximum daughter activity is at

A

tmax = [1.44 TpTd / (Tp - Td)] ln(Tp/Td)

ln() must be positive so (Tp/Td)

58
Q

No equilibrium occurs in what circumstance?

A

td>tp

59
Q

The parent isotope of 99mTc is mainly 99Mo, extraced from __________ ___________

A

fission products

60
Q

An alternative approach to the production of 99mTc is through an accelerator, based on the reaction __________________

A

100Mo(p,2n)99mTc

61
Q

Most I-131 production is via

A

neutron activation

irradiation of a tellurium (Te-130) target which becomes Te-131 and decays with a half-life of 25 min to I-131

62
Q

Neutron activated radionuclides of medical importance include

A

14C

32P

125I

131I

63
Q

Radionuclides produced via neutron activation tend to decay via _______

A

β-

64
Q

Two nuclear reactions commonly used to produce radionuclides using an accelerator are

A

(p,n)

(d,n)

65
Q

Cyclotron radionuclides of medical importance include

A

11C

13N

15O

18F

67Ga

111In

123I

201Tl

66
Q

The branching ratio of Mo-99 to Tc-99m is

A

.876

67
Q

Reaction cross sections are measured in units of

A

barns

(1b = 10-24 cm2)

68
Q

Flux density (ɸ) is measured in terms of

A

particles / unit area · sec

69
Q

Activation rate (R) per unit mass of target material is

A

R≈Δɸ/m

R≈(6.023× 1023)σ ɸ/A {activations / g sec}

A = gram atomic weight

70
Q

Anion

A

negatively charged ion

71
Q

Effective half-life equation

A

1/te = 1/tp + 1/tb

72
Q

Roentgen

A

It is the amount of gamma or x-rays required to produce ions resulting in a charge of 0.000258 coulombs/kilogram of air under standard conditions. Named after Wilhelm Roentgen, the German scientist who discovered x-rays in 1895.

2.58E-4 C/kg

73
Q

Nuclie

A

A general term referring to all known isotopes both stable (279) and unstable (about 2700) of the chemical elements.

74
Q

Measurement errors at the bottom of the dose calibrator can be between

A

3-6 %

75
Q

Dose calibrator response can be up to ________ off for sources placed laterally from the central axis.

A

10%

76
Q

For the geometry test - when pulling saline into the syringe (diluting the source volume), use a bent needle to

A

break the vacuum and prevent backflow into the dilution vial

77
Q

In geometry test for dose calibrator, one approach is to use multiple syringe, reading at 20% intervals. Syring sizes could be

A

1cc

3cc

5cc

10cc

78
Q

Geometry testing fails if the error exceeds

A

5%

79
Q

Dose calibrators are very long-lived systems, often used for well over

A

a decade or more

80
Q

Survey meter (Geiger-Mueller Detector) checks should be performed

A

daily with use

81
Q

Three different quality control measures for survey meters are

A

battery check

sealed source check

calibration

82
Q

The selection, use, calibration and quality assurance of dose calibrators is described in AAPM TG Report

A

181 (June 2012)

83
Q

The PET technologist should ensure the clock in the hotlab matches the clock in the console room this frequently

A

daily

84
Q

Clock accuracy should be within

A

1 minute , synchronized to a standard time (e.g., values transmitted to a cellular telephone or those maintained by NIST

85
Q

Physical inspection of a radionuclide calibrator should include

A

visual check for damaged source holders, keypads, buttons, switches

visual check for any small items in the well

visual check of the display screen

86
Q

System electronics associated with a radionuclide calibrator are gennerally done

A

using a manufacturer-provided diagnostic test

87
Q

Ba-133 half-life, decay mechanism and primary radiation

A

10.74 yr

e- capture

356 keV (62%)

Energies of photons MeV (intensity %/d):

.031 (.969), .035 (22.6%), .053 (2%), .0796 (3%), .081 (34%), .276 (7%), .303 (18%), .356 (62%), .383 (9%)

88
Q

Iodine escape peaks are more prominent with

A

lower energy x-rays due to the probability of photoelectric absorption interactions

89
Q

Secular equilibrium will occur when the half-life of the parent is roughly ________ x that of the daughter

A

100

90
Q
A

ABR Nuc Med (18 decks)

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