FINAL TQ PART IV Flashcards
effects of ionizing radiation?
biologic effects can penetrate matter -disrupts atomic structure -temp or perm cellular damage causes materials to fluoresce reacts with silver halide
name this definition:
energy is always transferred to any material with which it interacts
ionizing radiation
what are the considerations of the interactions with x-rays?
interaction with air
interaction with patient
interaction with image receptors like film and screens
what are the three types of interactions with matter?
penetration
absorption
scatter
what are the 5 basic interactions with matter?
coherent scatter pair production photodisintegration compton scatter photoelectric absorption
name this definition:
interaction with matter where the x-ray is absorbed and not scattered
photoelectric rxn
what does the photoelectric rxn yield?
characteristic radiation
what are the three products of the photoelectric effect?
photoelectron
characteristic radiation
positive ion
when is the PE rxn most likely to occur?
when the photon energy and electron BE are the same
for the Compton effect, what does a greater angle mean for energy? what happens when it hits the film?
less energy
the film darkens
what are the 4 factors that affect attenuation?
kilovoltage, inverse (decrease)
density, increase
atomic number, increase
electrons per gram of tissue, increase
why do we use the polyenergetic attenuation?
increase the beam quality you increase the beam hardening
name this definition:
measures the amount of radiation energy (E) absorbed per unit mass (M) of the absorbing medium
absorbed dose
what is the equation of the absorbed dose? units?
D=E/M
gray (Gy)
1 Gy=100 rads
1 rad=10 mGy
name this defn?
energy absorbed by the medium per unit length of travel
proportional to (particle charge) squared
inversely related to _____?
linear energy transfer (LET)
kinetic energy
what are the high linear energy transfer particles?
high or low penetrative
protons, neutrons, alpha particles
low
what are the low linear energy transfer particles?
high or low penetrative
photons, electrons, gamma and x-rays
high
name this definition?
attempts to quantify biologic damage from deposition of radiation in tissues
dose equivalent
what is the equation for dose equivalent (H)?
what are the units?
for this, the QF is measured in rads, what does this equal?
absorbed dose x quality factor
sievert
1 Sv=100 rem
1 rem=10 mSv
1 rem
heavily irradiated areas turn what color?
complete attenuation?
partial attenuation?
black
clear
gray
what are the layers of the film?
what is the affect of leaving in the film to develop for too long?
supercoat
emulsion layer
adhesive layer
film base
it turns everything black
sensitivity speck is found in which layer of the film? the emulsive layer is made of what and how? the sensitivity speck is what surface defect?
emulsive layer
silver halide with a cubic internal arrangement
AgS surface defect
the total fix time equals _____? (for the fixing bath)
2x clearing time
for processing temp, what are they for manual and automatic?
affect if temperature is too high?
68 degrees F
90-95 degrees F
film fog and overdevelopment
in the processing of film, what are the brown stains called that develop due to the wash problems or excessive fixing problems?
black film?
clear film?
chromatic stains
overdevelopment
clear film
processing time for auto vs manual?
auto is 90 sec
manual is 1 hour
what are the general considerations for handling film?
improper handling heat and humidity light radiation shelf life
because film is pressure sensitive, what should we avoid?
creasing film
rough handling of films/screens
dirt on hands
aging of film fog results in? how to prevent this?
loss of speed and contrast
film age fog
store the boxes upright to minimize film warping and sticking together
what are the primary function of intensifying screens?
shorter exposure times
advantages of screen-film advantages?
exposure w/o screen is sharpest but long exposures are unsafe and increase chance of patient motion
decrease tube mA and exposure times
decrease tube heat and increase tube life
what are the intensifying screens made of?
made of plastic or cardboard
reflective or absorptive layer
phosphor layer
protective plastic cover layer
typical intensifying screens range from what?
screen speed increases with?
30-50
- 2x screen
- increased thickness of phosphor film
- increased phosphor crystals
- reflective backing
speed of calcium tungstate is inversely related to_____? so higher speed means?
ability to record detail
less detail
why are rare earth screens better than calcium tungstate?
light conversion efficiency of the rare earth phosphors is greater
what is the green-sensitive film also called?
blue sensitive requires what safelite?
green sensitive requires what safelite?
orthochromatic film
amber safelite
red safelite
what are the two types of basic films?
thin emulsion, enhanced light sensitivity
thick emulsion, enhanced x-ray sensitivity
screen films
non-screen films
screen films
non-screen films
name this type of film?
enhanced light sensitivity, higher contrast, short grey scale and latitude
screen film
name this type of film?
exposed directly without screens
thicker emulsion than screen film
lower contrast, long grey scale and latitude
greater detail than screen film, but requires 20-50 times more exposure
non-screen film
what side of the fluoroscope should the physician stand?
image intensifier
