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22 Cards in this Set

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What is an AMU?
atomic mass unit that is 1/12 of C12 atom
What is the "liquid drop" theory of nuclear structure?
nucleons are a homogeneous mixture mass bound by strong force with outer nucleons less tightly bound due to repulsion of electrostatic forces
What is the "shell" model theory of nuclear structure?
like the Bohr model for electrons, the nucleons exist in shells
Explain the N/P ratio
ratio between the strong and electrostatic forces. lighter elements have a ratio of 1.0 and heavier 1.5
why are heavier elements higher?
heavier elements have additional neutrons which act as insulator
What are the most stable configuration for naturally occurring isotopes?
when there is an equal number of neutrons and protons, especially in multiples of 4, He-4, C-12, O-16, etc
What is negative beta decay?
isotope doesn't have enough protons so a neutron is changed into a proton in the daughter by giving off a beta particle and antineutrino
what are the equations for this?
N->P + e- + ν-
14C ->14N + β + ν-
C is the parent, N is the daughter where a neutron is changed into a proton giving off energy in the form a beta and nu particle or neutrino
o Same mass number but now different element as C has 6 protons and N has 7
• Mass must be conserved between parent and daughter
o Mp = Md + Me + Q (M = mass, Q = energy of emission)
What are neutrinos and how were they discovered?
There was excess energy emitted besides that of the beta particle so it was theorized that there was another particle.
what are they, and their origin?
they are nearly massless with no charge. the antineutrino comes from negative beta decay and neutrino comes from positive beta decay or positron emission and electron capture as well
What is positron decay?
Opposite of negative Beta decay
Too many protons, proton is changed into neutron
Positron and neutrino emitted resulting in annihilation which emits 1.02 MeV
2 photons emitted 180deg from each other with an emission of .511MeV, which adds up to 1.02 MeV
what are the equations for this?
P = n + β+ + ν
Example: 15O-> 15N + β+ + ν + 1.02 MeV
This is known as isobaric decay, emitted positron is annihilated upon meeting negatively charged electron producing 2 .511 MeV photons traveling 180deg apart from each other for a total of 1.02 Mev
Mp = Md + Me- + Me+ + Q
What is electron capture?
An element that has too many protons will “suck in” an electron from K shell will turn proton into neutron
2nd option instead of positron or beta plus decay (can do either, not understood how an element will “decide” to do which one, or both by different percentages)
When this happens characteristic x-rays are given off which is what our gamma cameras pick up
give ex and equation
Ex. 201Tl used in cardiac imaging
Mp + Me = Md + ϕ + Q (where ϕ is the binding energy of captured electron)
What is isomeric transition and gamma decay?
After emission of a radioactive particle the nucleus can be left in an excited state for a limited time
The nucleus will eventually decay to the ground state by emission of a gamma ray
show how Tc 99m is made from Mo
99Mo->99mTc + β- + ν- where “m” means metastable, holds on to energy for a certain amount of time
what is this time?
in Tc it is 6 hrs, which is what a half life is, which is ideal for nuclear medicine.
What happens when Tc 99m decays to ground state?
99mTc->99Tc + γ
This is known as isomeric transition. The only difference between 99mTc and 99Tc is the energy state. These are known as isomers. (2 identical elements with different energy states)
What is Alpha decay?
Heavy elements decay by emission of He nucleus (2P & 2N)
Atomic # drops by 2 and mass # by 4
How heavy does an element have to be to do alpha decay?
All alpha emitters have an atomic number >82 except Sm147 which is 62
equation for this?
Xaz->Xa-4,z-2 +He4,2 + ν + Q
Q is the energy of emission which is divided between parent and daughter nucleus. The daughter nucleus “recoils” when alpha particle emitted
What is an auger electron?
This happens when a gamma ray emitted by the nucleus interacts with orbital electron instead of traveling out.
This results in a ejected electron called an auger electron
what kind of energy is this and how does this hinder imaging?
Monoenergetic (one energy emitted, not a spectrum)
This is not good since it takes away gamma emissions for imaging
On a decay schematic explain the direction of arrows?
down to right - beta decay
down to left - positron decay, electron capture or alpha decay
straight down - gamma decay
an arrow to the right on a decay schematic indicates which direction the daughter is created on the periodic table?
To the right, adding a proton, left is opposite, losing proton(s)
Can Electron capture and positive beta (positron decay) happen at the same time?
Yes, they happen together at different percentages adding up to 100%
Give the 2 equations showing both EC and positron decay for 22Na->22Ne
EC: 22Na->22Ne + X-ray(characteristic) + ν
Β+: 22Na->22Ne +β+ + 1.02 MeV(from annihilation) + ν
What are the 2 isotopes used to check the dose calibrator?
Co57 and Cs137
What are the 2 units used to measure radiation and what is the factor between them?
Curie - 3.7 x 10E10 dps
Bequerel - 1 dps
37 MBq = 1 mCi
factor of 37
What is the decay equation?
A1 = A0 e-λt