Physics/Materials Flashcards
What is the half life of 99mTc
6 hours
How is 99mTc made?
99Mo generator
Photon energy in keV of 99mtc?
140keV gamma waves only
A curie (Ci) = how many atoms disintergration?
3.7 x 10 -10 per second
1 Bq (becquerel) = how many atoms distergration?
1 per seconds
Rad and Gray = what?
Radiation absorbed dose
I131 half life?
8 hours
I131 emits what?
Beta and gamma rays (364keV)
How is I131 made..in what machine?
Fission
What is indium 111 half life?
2.8 days
How is indium 111 made…in what machine?
Cyclotron
What is the atomic number?
Number of protons
Atomic weight?
The avg of the atomic masses of all occuring isotopes
Atomic mass?
Number of protons and neutrons
As atomic mass increases the number of neutrons has to what to keep the atom stable?
increase (more gluons)
Elements to the left of the “line of stability” are considered neutron rich or proton poor and decay how?
Beta minus decay - these are typically made by fission
Elements to the right of the “line of stability” are considered neutron poor or proton rich and decay how?
Beta + decay - these are typically made by cyclotons
PET scan detects what energy of photons?
511keV
Types of decay (5 of them)
- Alpha
- Negatron
- Positron
- Isomeric
- Electron capture
Alpha decay gives off what type of particle?
Alpha (4He+2) - Not used in diagnostic imaging due to high LET
What is an example of alpha decay?
radon
What is negatron decay?
Happens in neutron rich atoms. A neutron is turned into a proton and a negatron + neutrino are released.
What is a neutrino?
Massless and chargeless particle that means nothing to imaging
What are the two types of negatron decay?
- Pure beta emitter - P32
2. Gamma and beta emitter - I131
What is isomeric decay?
It is a beta decay (negatron)… however, the newly formed atom (after the beta and neutrino are released) holds on to the gamma and waits to release it. These transitional molecules are indicated by an “m”. Ex. 99Mo —(negatron release)–99mTc—-(gamma radiation release) —- 99Tc
What is the middle atom call that is signified by an M in an isomeric decay?
Metastable
What is the half life of 99Mo
109min
What is positron decay?
Proton rich molecules change a proton into a neutron and release a positron. This has a energy threshold of 1.022 MeV (two positrons). 18FDG
Electron Capture is what and when does it happen?
It happens when a proton-rich nuclide does not reach the energy threshold to undergo positron decay. Therefore it just sucks in a K-bond electron into the nucleus to form a neutron. A neutrino and gamma ray can be given off. This is the most desirable reaction because no particular radiation is released.
What is the transient equilibrium when discussing 99Mo and 99mTc?
It is when the daughter has the same decay rate as the parent.
When (hours) is the greatest degree of 99mTc reached in a generator?
23h
How long is a 99Mo generator useful for?
2 weeks
What is the product of a 99Mo generator?
Na99mTc04 (sodium 99mTc- pertechnetate)
How do you test 99mTc for 99Mo breakthrough?
Put a lead absorbed in front of a ionization chamber that will block all the 140keV from the 99mTc but not the 740-780keV from the 99Mo.
What is the energy of the gamma rays from 99Mo?
740-780keV.
Where are the primary locations for 99mTc after intravenous injection?
Salivary gland
Gastric mucosa
Thyroid gland
Chorid plexus
What is the difference between ionizing and excitement?
Ionizing removes electrons creating ions
Excitement moves electrons to a higher energy level.
Why do detectors need amplification?
The energy deposited from decay is very small usually
What are the 6 ways electromagnetic energy (x-rays and gamma rays) interact with matter?
- Nothing
- Photoelectric
- Compton scatter
- Coherent scatter
- Pair production
- Nuclear collisions
What is the most predominant interaction of x-rays and gamma rays when interacting with matter?
Compton scatter
Geiger-Mueller counters can not tell you what?
What type of radiation
Total amount of energy deposited
All counter do is tell you a radiation event happened.
Detectors that tell you the amount of energy deposited are called?
Dosimeters
What type of crystals are used in a gamma camera scintillator?
NaI (thalium)
What does LEAP stand for?
Low energy all purpose
What are the two things you need to think about when discussing collimators?
The energy of the pharmaceutical
The resolution/sensitivity you want
Besides increasing thickness of the collimator, what else can influence spatial resolution?
The distance the patient is from the plate… think of an air gap.
What type of collimator causes magnification?
converging collimator holes… meaning the holes are converging towards the patient
What type of collimator causes minification?
Diverging collimator holes.. meaning the holes are diverging towards the patient.
Pinhole collimators cause the image to do what?
Be completely inverted
They can be minified, magnified or the same depending on how far the patient is from the collimator and how thick the pinhole (cone) is.
Why is NaI used for scintillation?
High Z allows for more Photoelectric effect to happen.
What is the difference between SPECT scintillation and PET?
PET has bismuth germanate (BGO) detectors which are way more sensitive to 511keV than NaI detectors in SPECT imaging.
LET units are?
KeV/um
1 Gray = ? rads
100 rads
What do you multiple Gray/rad by to get your dose equivalent?
Quality factor
What is the qualtiy factor for x-rays, gamma rays and beta particles?
1
What is the quality factor for neutrons/protons and alpha particles?
5-10 for neutrons and protons
20 for alpha particles
