Nuclear Physics Review Flashcards
Pass Test
A neutron undergoes B- decay, what is generated?
Proton, electron, and anti-neutrino (p+e-+~v)
What are two elements that undergo B- decay?
99Mo42
131I53
What are the decay products from 99Mo42?
99mTc43 + e- + ~v
Decay products from 131I53?
131Xe54 + e- + ~v
What happens in B+ decay?
A proton decays to neutron, positron, and neutrino
P –> n + e(+) + v
B+ decay
What are 2 elements that undergo B+ decay?
18F9
15O8
Products of 18F9 decay?
18O8 + e(+) + v
Products of 15O8?
15N7 + e(+) + v
What are the two annihilation formulas?
e- + e+ = 2y
e- + B+ = 2y
How much energy does each Y have after annihilation?
511 KeV
What element did they describe as undergoing Isomeric transition?
99mTc43
What’s another name for isomeric transition?
y decay
What is left after 99mTc43 undergoes gamma decay?
99Tc43 + y
How is an Auger electron produced?
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.
Describe the primary and secondary effects of electron capture.
Primary: orbital electron is absorbed into nucleus and combined with proton to form a neutron and neutrino.
Secondary: emissionof x ray or Auger electrons
Formula for disintigration rate at time t?
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
half life of Tc-99?
6 hr
lambda for Tc-99?
0.116
SI unit of decay?
Becquerel = 1 disintegration per second
Traditional unit of radioactivity?
Curies (Ci)
How many decays per second in 1 Ci?
3.7x10^10 dps (not damage per second yo, or is it… hmm)
1 mCi = XX MBq?
1mCi = 37 MBq
1 gy (gray) = How many rad?
1Gy = 100 Rad
Units of Gy?
Joules/kg
What is effective half life?
Time to reduce radiopharmaceutical in the body by one half due to functional clearance and radioactive decay
Effective half life formula?
1/Te = 1/Tp + 1/Tb
or
Te = (Tp * Tb)/(Tp+Tb)
When can you cut the crap with effective half life and make a bunch of assumptions without getting fucked?
IF Tp»_space; Tb, then Te ~ Tb
and, conversely
Tb»_space; Tp, then Te ~ Tp
In a Tc-99m/Mo-99 generator, the time of maximum activity is approximately?
24 hours
Elution:
Eluate:
Eluant:
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)
Radionuclides that undergo B+ decay?
11C 13N 15O 18F 82Rb
Radionuclides that undergo B- decay?
32P 89Sr 99Mo42 131I 153Sm
Radionuclides that undergo EC decay?
111In 67 Ga 123I 125I 201Tl
Types of Radiation detectors? 7 of them
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)
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?
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
Describe how signal strength is related to energy deposited in the ionization chamber region.
In IC region signal strength is proportional to energy deposited.
What is the IC region used to measure?
The amount of radiation (i.e. exposure, air kerma)
What does a dose calibrator measure? When do we use it?
Activity only
Use to assay every patient dose prior to administration.
Dose calibrators have quality control measures including: Constancy Linearity Accuracy Geometry How often are each measured?
Constancy: Daily
Linearity: quarterly
Accuracy: Yearly
Geometry: On install
In the GM region, how are signal strength and energy deposited related?
In this region signal strength and deposited energy are independent of each other.
Which IC detectors are stable with respect to voltage?
Ionization detector and Geiger counter
Which IC detectors are capable of energy discrimination?
Ionization detector and proportional counter
What are the main components of a scinitillation detector?
Scintillator
photomultiplier tube
NM - inorganic solid scintillator (Nal(TI)) and a PMT
What is the purpose of a collimator?
establish position relationship between gamma photon source and detector
Purpose of scintillator?
convert gamma photons to blue light photons
A pmt is for?
converting blue photons to electrons and increasing the number there-of
The electronic devices measure:
Pulse height analysis
position analysis
These tell us what?
Pulse height: est. energy deposited in each detection and enables scatter rejection.
Position: center of luminescent intensity
Types of collimators?
Which are specifically for certain organs, and what organs?
Parallel hole collimator (most used)
Pin-hole: for thyroid
Converging: for brain and heart
How is signal position determined?
Center of mass calculation
avg. X = SUM(Signal * distance)/SUMSignal
see slides for better equation
What does back projection of sinogram data lead to?
Blurring in image - streaks and star like artifacts
Types of iterative reconstruction?
- Filtered back projection (may not be a type of this, slide is unclear)
- MLEM: Maximum liklihood expectation maximization
- OSEM: Ordered Subsets expectation maximization (common algorithm)
Type of iterative recon used commonly for PET, SPECT and CT?
OSEM
In PET, at what delta t does a coincident event register?
delta t <5 (to 12) ns
What B+ emitters are used in PET?
What do they decay to?
18F9 --> 18O8 15O8 --> 15N7 13N7 --> 13C6 11C6 --> 11B5 82 Rb37 --> 82Kr36 And associated e+ and v for each.
What determines the ULTIMATE spatial resolution in PET?
Uncertainties in annihilation: annihilation location and residual particle momentum. ~2mm
true or false, true coincidences for a true distribution of radioactivity
True, duh
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?
No collimators in a PET scanner
What does the absence of lead collimators do for PET?
improves:
Detection efficiency (count rate)
spatial resolution
Detector materials used by: GE? Seimens? Philips? All?
GE: BGO
Semens: LSO
Philips: GSO
All: LYSO
What are the advantages of PET? How so?
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
Time of flight improves?
spatial resolution by compensating for intrinsically conserved momentum of coincident gamma photons
What scintillator material is used for time of flight?
What is the accuracy?
LYSO
8.8 cm of accuracy
ToF is used to…
improve signal to noise ratio, leading to either better images or shorter scans
What types of PET data corrections are done?
Which is most important?
What do they do?
Hint, there are 5.
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)
Semiquantatative PET uses standard uptake value which is defined as?
ratio of activity concentrations
or
SUV = conc. in lesion/conc. in whole body (each is in MBq/kg)
What is the usual cut-off between malignant and non-malignant pathology?
SUV ~ 2.5
SUV will depend on?
physiologic condition uptake time fasting state image noise resolution ROI definition
Every PET study is compensated for attenuation, what is needed for this?
attenuation map from CT
What does absorbed dose refer to?
The units for this are?
Absorbed dose is the energy deposited in a unit mass of absorber.
1 Gy = 1J/kg
1 Gy = 100 rad
What is equivalent dose?
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.
Traditional unit of equivalent dose?
SI unit?
Conversion factor?
Trad = rem SI = Sv 1Sv = 100 rem
Equation for equivalent dose Ht?
Ht = Dt * omegaR
Dt: absorbed dose in tissue
OmegaR: weighting factor denoting relative bio damage for type of radiation.
How is effective dose obtained?
By taking into account the equivalent dose to all exposed organ, as well as each organs relative radiosensitivity.
E = SUM (Ht * OmegaT)
WT for red marrow, colon, lungs, stomach, breast?
0.12 each
WT for gonads?
0.08
WT for bladder, skin, salivary glands, bone surfaces?
0.01 each
WT for all else?
0.12 Total
Annual effective dose limit?
50 mSv
Effective dose cumulative?
10 mSv * age (years)
