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Radiology Physics > Nuclear Physics Review > Flashcards

Nuclear Physics Review Flashcards

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1
Q

A neutron undergoes B- decay, what is generated?

A

Proton, electron, and anti-neutrino (p+e-+~v)

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2
Q

What are two elements that undergo B- decay?

A

99Mo42

131I53

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3
Q

What are the decay products from 99Mo42?

A

99mTc43 + e- + ~v

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4
Q

Decay products from 131I53?

A

131Xe54 + e- + ~v

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5
Q

What happens in B+ decay?

A

A proton decays to neutron, positron, and neutrino

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6
Q

P –> n + e(+) + v

A

B+ decay

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7
Q

What are 2 elements that undergo B+ decay?

A

18F9

15O8

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8
Q

Products of 18F9 decay?

A

18O8 + e(+) + v

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9
Q

Products of 15O8?

A

15N7 + e(+) + v

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10
Q

What are the two annihilation formulas?

A

e- + e+ = 2y

e- + B+ = 2y

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11
Q

How much energy does each Y have after annihilation?

A

511 KeV

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12
Q

What element did they describe as undergoing Isomeric transition?

A

99mTc43

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13
Q

What’s another name for isomeric transition?

A

y decay

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14
Q

What is left after 99mTc43 undergoes gamma decay?

A

99Tc43 + y

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15
Q

How is an Auger electron produced?

A

Filling of an inner shell vacancy of an atom is accompanied by emission of an electron from the same atom. Most often a photon is released by occasionally an electron is ejected.

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16
Q

Describe the primary and secondary effects of electron capture.

A

Primary: orbital electron is absorbed into nucleus and combined with proton to form a neutron and neutrino.

Secondary: emissionof x ray or Auger electrons

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17
Q

Formula for disintigration rate at time t?

A

A(t) = lambda * N(t)
A(t): disinitegration rate at t in decays per sec
N(t) = # nuclei at time t
lambda = ln2/half life (T1/2) = 0.693/half life

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18
Q

half life of Tc-99?

A

6 hr

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19
Q

lambda for Tc-99?

A

0.116

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20
Q

SI unit of decay?

A

Becquerel = 1 disintegration per second

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21
Q

Traditional unit of radioactivity?

A

Curies (Ci)

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22
Q

How many decays per second in 1 Ci?

A

3.7x10^10 dps (not damage per second yo, or is it… hmm)

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23
Q

1 mCi = XX MBq?

A

1mCi = 37 MBq

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24
Q

1 gy (gray) = How many rad?

A

1Gy = 100 Rad

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25
Q

Units of Gy?

A

Joules/kg

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26
Q

What is effective half life?

A

Time to reduce radiopharmaceutical in the body by one half due to functional clearance and radioactive decay

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27
Q

Effective half life formula?

A

1/Te = 1/Tp + 1/Tb
or
Te = (Tp * Tb)/(Tp+Tb)

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28
Q

When can you cut the crap with effective half life and make a bunch of assumptions without getting fucked?

A

IF Tp&raquo_space; Tb, then Te ~ Tb
and, conversely
Tb&raquo_space; Tp, then Te ~ Tp

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29
Q

In a Tc-99m/Mo-99 generator, the time of maximum activity is approximately?

A

24 hours

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30
Q

Elution:
Eluate:
Eluant:

A

Elution: The process of extracting one material from another by washing with a solvent to remove adsorbed material from an adsorbent
Eluate: A liquid solution from eluting
Eluant: A substance used as a solvent in separating materials in elution (saline)

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31
Q

Radionuclides that undergo B+ decay?

A 
11C
13N
15O
18F
82Rb
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32
Q

Radionuclides that undergo B- decay?

A 
32P
89Sr
99Mo42
131I
153Sm
33
Q

Radionuclides that undergo EC decay?

A 
111In
67 Ga
123I
125I
201Tl
34
Q

Types of Radiation detectors? 7 of them

A 
Survey meters (gas-filled detector) 
Ionization chambers (IC)
Geiger Müeller (GM)
Dose calibrator (gas-filled detector)
Well counter (scintillation detector) 
Thyroid probe (scintillation detector) 
Miniature g-probe (scintillation)
35
Q

In a gas filled ionization chamber, what are the Bias voltage ranges for the followin regions:

  • Recombination region?
  • Ionization Chamber region?
  • Proportional counter region?
  • Geiger counter region?
  • Spontaneous discharge?
A

Recombination region: <300 V

Ionization chamber region: 300 V - 600V

Proportional counter region: 600V – 900V

Geiger counter region: 900V - 1200V

Spontaneous Discharge region: >1200V but we really don’t give a shit about this one

36
Q

Describe how signal strength is related to energy deposited in the ionization chamber region.

A

In IC region signal strength is proportional to energy deposited.

37
Q

What is the IC region used to measure?

A

The amount of radiation (i.e. exposure, air kerma)

38
Q

What does a dose calibrator measure? When do we use it?

A

Activity only

Use to assay every patient dose prior to administration.

39
Q 
Dose calibrators have quality control measures including:
Constancy
Linearity
Accuracy
Geometry
How often are each measured?
A

Constancy: Daily
Linearity: quarterly
Accuracy: Yearly
Geometry: On install

40
Q

In the GM region, how are signal strength and energy deposited related?

A

In this region signal strength and deposited energy are independent of each other.

41
Q

Which IC detectors are stable with respect to voltage?

A

Ionization detector and Geiger counter

42
Q

Which IC detectors are capable of energy discrimination?

A

Ionization detector and proportional counter

43
Q

What are the main components of a scinitillation detector?

A

Scintillator
photomultiplier tube
NM - inorganic solid scintillator (Nal(TI)) and a PMT

44
Q

What is the purpose of a collimator?

A

establish position relationship between gamma photon source and detector

45
Q

Purpose of scintillator?

A

convert gamma photons to blue light photons

46
Q

A pmt is for?

A

converting blue photons to electrons and increasing the number there-of

47
Q

The electronic devices measure:
Pulse height analysis
position analysis
These tell us what?

A

Pulse height: est. energy deposited in each detection and enables scatter rejection.

Position: center of luminescent intensity

48
Q

Types of collimators?

Which are specifically for certain organs, and what organs?

A

Parallel hole collimator (most used)
Pin-hole: for thyroid
Converging: for brain and heart

49
Q

How is signal position determined?

A

Center of mass calculation
avg. X = SUM(Signal * distance)/SUMSignal

see slides for better equation

50
Q

What does back projection of sinogram data lead to?

A

Blurring in image - streaks and star like artifacts

51
Q

Types of iterative reconstruction?

A
  1. Filtered back projection (may not be a type of this, slide is unclear)
  2. MLEM: Maximum liklihood expectation maximization
  3. OSEM: Ordered Subsets expectation maximization (common algorithm)
52
Q

Type of iterative recon used commonly for PET, SPECT and CT?

A

OSEM

53
Q

In PET, at what delta t does a coincident event register?

A

delta t <5 (to 12) ns

54
Q

What B+ emitters are used in PET?

What do they decay to?

A 
18F9 --> 18O8
15O8 --> 15N7
13N7 --> 13C6
11C6 --> 11B5
82 Rb37 --> 82Kr36
And associated e+ and v for each.
55
Q

What determines the ULTIMATE spatial resolution in PET?

A

Uncertainties in annihilation: annihilation location and residual particle momentum. ~2mm

56
Q

true or false, true coincidences for a true distribution of radioactivity

A

True, duh

57
Q

What types of collimators are incorporated into PET scanner? For what are they used? What are their limitations? What is the typical material?
What is the average weight of each collimator?
What is the average wing speed of an african swallow?

A

No collimators in a PET scanner

58
Q

What does the absence of lead collimators do for PET?

A

improves:
Detection efficiency (count rate)
spatial resolution

59
Q 
Detector materials used by:
GE?
Seimens?
Philips?
All?
A

GE: BGO
Semens: LSO
Philips: GSO
All: LYSO

60
Q

What are the advantages of PET? How so?

A

No collimators –> higher count rate/detection efficiency and better spatial resolution

Ring detectors –> higher detection efficiency

Block detectors –> higher detection efficiency and better spatial resolution

61
Q

Time of flight improves?

A

spatial resolution by compensating for intrinsically conserved momentum of coincident gamma photons

62
Q

What scintillator material is used for time of flight?

What is the accuracy?

A

LYSO

8.8 cm of accuracy

63
Q

ToF is used to…

A

improve signal to noise ratio, leading to either better images or shorter scans

64
Q

What types of PET data corrections are done?
Which is most important?
What do they do?
Hint, there are 5.

A

Attenuation: most important, CT based

Normalization: corrects for variable detector performance

Random coincidences: delays coincident time window - 64ns

scattered radiation: models transmission and emission data and extrapolates from tails of projections

dead time: generates empirical models (whatever the fuck those are in this context)

65
Q

Semiquantatative PET uses standard uptake value which is defined as?

A

ratio of activity concentrations

or
SUV = conc. in lesion/conc. in whole body (each is in MBq/kg)

66
Q

What is the usual cut-off between malignant and non-malignant pathology?

A

SUV ~ 2.5

67
Q

SUV will depend on?

A 
physiologic condition
uptake time
fasting state
image noise
resolution
ROI definition
68
Q

Every PET study is compensated for attenuation, what is needed for this?

A

attenuation map from CT

69
Q

What does absorbed dose refer to?

The units for this are?

A

Absorbed dose is the energy deposited in a unit mass of absorber.

1 Gy = 1J/kg
1 Gy = 100 rad

70
Q

What is equivalent dose?

A

HT (In seiverts), this is a quantity that expresses absorbed dose across an organ or tissue with a weighting factor for type and energy of radiation.

71
Q

Traditional unit of equivalent dose?
SI unit?
Conversion factor?

A 
Trad = rem
SI = Sv
1Sv = 100 rem
72
Q

Equation for equivalent dose Ht?

A

Ht = Dt * omegaR
Dt: absorbed dose in tissue

OmegaR: weighting factor denoting relative bio damage for type of radiation.

73
Q

How is effective dose obtained?

A

By taking into account the equivalent dose to all exposed organ, as well as each organs relative radiosensitivity.

E = SUM (Ht * OmegaT)

74
Q

WT for red marrow, colon, lungs, stomach, breast?

A

0.12 each

75
Q

WT for gonads?

A

0.08

76
Q

WT for bladder, skin, salivary glands, bone surfaces?

A

0.01 each

77
Q

WT for all else?

A

0.12 Total

78
Q

Annual effective dose limit?

A

50 mSv

79
Q

Effective dose cumulative?

A

10 mSv * age (years)

Radiology Physics (2 decks)

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