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HSCI 202 Exam 3
n/a
69
Health Care
Undergraduate 4
11/17/2009

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Cards

Term
radiation burden depends on what 3 things?
Definition
medical applications (therapy vs. diagnosis), the amount of radioactive material injected (injected dose), type of radiation and energy (high or low)
Term
excitation of alpha particles
Definition
electrostatic attraction raises an electron to a higher energy state... when they drop back to normal state, they may emit electromagnetic radiation such as light or fluorescence
Term
ionization of alpha particles
Definition
kinetic energy is lost from the alpha particle, the velocity of the particle is reduced... when it loses all its energy, it combines wtih 2 free electrons to form helium and the radiation no longer exists
Term
rank the 4 types of particles from lowest to highest penetrating distance
Definition
goes in alphabetical order: alpha < beta < gamma and xrays < neutron
Term
due to their small/large size and fast/slow motion, alpha particles lose their energy quickly/slowly
Definition
large, slow, quickly
Term
what kind of beta particle loses excess kinetic energy by ionization and excitation to become an ordinary electron?
Definition
negatron
Term
what kind of beta particle loses excess kinetic energy by ionization and excitation and then reacts with an electron by annihilation?
Definition
positron
Term
___ is the combo of a positron with an electron, resulting in the production of 2 511 keV gamma rays going in the opposite direction.
Definition
Annihilation
Term
how do the velocities of alpha and beta particles compare?
Definition
beta > alpha
Term
Bremsstrulung
Definition
something about transferring energy from beta particles
Term
the energy of what particle follows a typical Guassian distribution
Definition
negatron
Term
Bremsstrahlung increases/decreases with higher atomic number absorbers
Definition
increases
Term
"braking radiation" or "deceleration radiation"), is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus.
Definition
Bremsstrahlung
Term
Specific Ionization (SI) for beta particles. how does this compare to alpha?
Definition
50-300 ip/cm in air -- much lower than alpha
Term
What is the fate of positrons? what is this useful in?
Definition
they combine with electrons to form 2 gamma photons, traveling in opposite directions. this is useful in PET (positron emission tomography) imaging
Term
lower energy = higher/lower penetrating range and higher/lower SI
Definition
lower, higher
Term
higher energy B rays produce more/less Bremsstrahlung
Definition
more
Term
3 interaction mechanisms for gamma spectroscopy
Definition
photoelectric absorption (for low energy gammas), compton scattering, and pair production (for high energy)
Term
__ is the ideal interaction process for measuring the energy of the original gamma ray. How does it work?
Definition
photoelectric absorption -- incident gamma ray photon disappears and a photoelectron is produced in its place -- the effect is the liberation of a photoelectron, which carries off mos the the gamma ray nergy
Term
result of compton scattering
Definition
a recoil electron and scattered gamma-ray photon
Term
result of pair production
Definition
incident gamma ray photon completely disappears -- occurs near intense electron field near protons and creates an electron-positron pair
Term
how are gamma photons detected?
Definition
a flash of light
Term
medical applications of SPECT
Definition
lungs, heart, brain,
Term
Coincidences of PET detectors
Definition
real (useful), scatter, and random
Term
beta particle emitters in medicine
Definition
can deposit and tumor cells and kill them, Y-90 (a pure beta-emitter) used to target other cancer cells
Term
why are beta particle emitters useful in medicine?
Definition
they penetrate deep enough to get into large, heterogeneous tumors, they yield a homogeneous dose even when heterogeneously distributed in a tissue
Term
How do beta particles work to kill cancer cells?
Definition
produce free radicals that are able to react wtih the DNA of the tumor and kill it
Term
SIR-Sphere radiation
Definition
used to kill liver tumors via a process called "SIRT" or selective external radiation therapy
Term
Who is in charge of radiation safety?
Definition
Nuclear Regulatory Commission (NRC), nuclear practitioners, and Health Physicists
Term
4 factors influencing external hazards of radiation
Definition
exposure level, exposure rate, type of radiation (alpha, beta, gamma), energy level, and amount of activity (more activity = more exposure)
Term
factors affecting internal radiation hazard
Definition
amount of activity (more = more expsure), chemical form, type of radiation, half life, effective half life
Term
combination fo the rate of excretion (biological half life) with the physical half liffe
Definition
effective half life
Term
when must personnel monitoring equipment be used?
Definition
when working in areas where there is likely exposure in excess of 10% of the maximum permissible exposure
Term
Spin-Echo (SE) pulse sequences flips the magnetic moment of the proton completely into the ___ plane. Due to ____ interactions, the Mxy decays with time T2
Definition
transverse (xy), spin-spin
Term
T2 relaxivity is a ____ interaction
Definition
spin-spin
Term
T1 relaxivity is a ____ interaction
Definition
spin-lattice
Term
when a magnetic moment (a proton) is placed within an external magnetic field, a force or torque acts on it causing it to precess (spin like a top)
Definition
lamor frequency
Term
transverse plane is the __ plane, external magnetic field is in the __ direction
Definition
xy, z
Term
I = nuclear spin quantum number. if I=0, then? If I=1,2,3, then? If I=1/2,3/2,5/2, then?
Definition
I=0 - even atomic number, no MR potential :: I=1,2,3 - odd atomic number, even atomic weight :: I=1/2, 3/2, 5/2 - odd atomic wieght (odd number of portons and even number of neutrons or vice versa)
Term
scatter coincidences are dependent on?
Definition
object size and attenuation coefficient (compton scattering) of the object
Term
3 categories of coincidences in PET sensitivity
Definition
true, scattered, and random
Term
spatial resolution of PET scanning can be blurred by what 3 things?
Definition
geometry, non-collinearity, positron range
Term
a filter on a CT scanner does what?
Definition
make the image more clear
Term
to minimize the effects of T2 to our signal in MRI, what 2 things do we do?
Definition
choose small TE, maximal TR
Term
to minimize the effects of TI in MRI, what 2 things do we do?
Definition
choose very long TR, maximal TE
Term
MRS = ?
Definition
magnetic resonance spectroscopy
Term
3 cardinal rules to radiation exposure and dose
Definition
time, distance, shielding
Term
distance radiation can travel
Definition
alpha < beta < gamma
Term
radiation exposure will decrease as the distance increases... this is defined by what law?
Definition
inverse square law
Term
what types of shielding materials are needed for each type of radiation?
Definition
increase with greater distance... alpha only needs paper or skin, beta needs plastic in combo with lead, gamma and x rays need high density lead
Term
the ____ is characteristic of a given material in terms of radiological shielding. it is proportional to the density and atomic number of the substance. the ____, on the other hand, is often used to compensate for density.
Definition
linear attenuation coefficient (u).. mass attenuation coefficient (um)
Term
ice, water, and steam have the same/different linear attenuation coefficient and the same/different mass attentuation coefficient?
Definition
different linear, same mass
Term
are natural or man-made sources of radiation exposure to humans greater?
Definition
natural
Term
of the natural sources of radiation exposure, which has the most effect on man? of the man-made sources?
Definition
radon, medical imaging
Term
___ and ____ radiation are particles. ___ radiation is electromagnetic waves.
Definition
alpha and beta, gamma
Term
long periods of exposure to alpha and beta radiation can cause _____. short term exposure usually does not have a significant effect except when ___, ____, or ______.
Definition
heat burns ... ingested, inhaled, or through an open wound
Term
the ___ is used to express the amount of gamma radiation exposure. why isn't this entirely helpful for humans?
Definition
Roentgen (R) - it only states the amount of exposure, not the dose absorbed
Term
a ___ relates the different types of radiation to the energy they impart. it is the basic unit of absorbed dose of radiation.
Definition
RAD (radiation absorbed dose)
Term
1 roentgen = __ RAD
Definition
1
Term
____ relates the does of any radiation to the biological effect of that dose.
Definition
REM - roetgen equivalent man
Term
for gamma and beta radiation, 1 rad = __ rem. for alpha, 1 rad = ___ rem
Definition
1, 20
Term
radiation exposure rate is expressed in what units?
Definition
roentgen/hr
Term
SI unit equivalents
Definition
Gray (Gy) = 100 rad, sievert (SV) = 100 rem
Term
general public radiation dose limit and occupational dose limit
Definition
public = 100 mrem/yr ... occupational = 5000 mrem/yr
Term
removal of electrons is called ____. when this happens in the body as a result of collision of radiation with cells, the result is human sickness
Definition
ionization
Term
each person differs in their biological response to a given radiation dose due to what 5 factors?
Definition
age, sex, diet, body temp, overall medical health
Term
____ occurs when an individual is exposued to a large dose of radiation in a short amount of time. doses greater than ___ rem/rad for gamma rays
Definition
acute radiation sickness, 100 rem/rad
Term
symptoms of acute radiation sickness
Definition
changes in blood cells, vascular changes, skin irritation, gi effects, fever, flu-like symptoms, hair loss
Term
4 stages of acute radiation sickness
Definition
prodromal phase (48 hrs), latent phase (days to weeks), manifest illness (weeks to months), recovery or death
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