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RAD-171 The prime Factors
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what is APR
anatomically programmed radiography
what is AEC
what does it control and what does it do
automatic exposure control
controls wall bucky and table
and they are sensors that control length of exposure and wait for predetermined radiation to hit it
what factors affect our quality of the beam
kVp and filtration
what technical factors allow more interactions to occur
kVp
what many factors affect our quantity
mAs
filtration
kvp SID collimation
certain body part
efficiency of the tube anode heel effect
certain pathology
what are three factors that effect xray emission that is under control of the radiographer
mAs kVp SID
what happens when you double ma
what happens to your image when you double mAs
double in the number of electrons crossing the tube
more dark
what is mA
measurement of tube current sent to the filament per second
_____ and _____ are directly proportional to the # of xray created
mA and time
mA stations between 25-200 and 20-1200 use what size filament
what will be the difference in your image
25-200 small filament
200-1200 large filament
same radiation but difference in detail
what is the controlling factor of radiographic density/IR exposure
mAs (milliamerage per second)
In regards to film what is the degree of blackening on a radiograph
density
what is IR exposure
how many xrays interact with IR
what increases as mAs increases and same applies as mAs decreases
density/IR exposure
When using film what happens if mAs is cut in half
your image will appear two times lighter
what is the reciprocity law
what whens when mAs is constant
List examples
law that states the density on an xray film/IR exposure is proportional to the intensity and duration of the xray exposure
as long as the ma is constant any combination of mAand exposure time(s) will create the same density/IR exposure
Ex.200 mA x .1 = 20mAs
100 mA x.05=20mA
what is brightness
how dark or light
digital
image appears on monitor
If your original film was acceptable (okay) what would you to view small differences on
film
increase by mas 30%
what is the primary controller of density/IR exposure
and what decreases as radiographic density/IR exposure decreases
mas (both)
what happens to your image is mas is double or cut in half on
film
mas double = twice as dark
mas is cut in half = twice as light
what is density
traditional term for infrared (IR) exposure to film
it is the amt of silver deposited on hard copy film image
what does it mean if your exposure numbers are over or below the index (svalue) range
it means the image was under exposed or over exposed
what is the direct square law pertaining to mas
what is the formula
it means it has a direct relationship necessary to compensate for the change in intensity and IR exposure
mAs 1 over mas2 = distance a squared over distance 2 squared
explain direct square law in your own words
if you double the distance you are going to need 4x more mas or radiaition
if you cut the distance in half you will 4x less radiaiton
maintaing a certain amount of density meanas we are maintaining a certain amount of _____
darkness
when in doubt about choosing if an image is too dark or too light the best option would be too ________
but what is the cost of doing this
over expose the patient
cost the patients recieving more radiaition than needed
what is the one factor that affects certain use of mA
SID
if 10 mAs were used with a 40'' SID, what new mAs would be needed to maintain density if the SID was changed to 80''
40 mAs since the distance was doubled you have to increase the mAs by 4x more
what unit of measurement is the inverse square law measured in
roentgen or mR
what is the inverse square law (brief definition)
intensity of radiation is inversely related to square of distance between object and source
what is contrast
the differentiation betwe the shades of gray
if an image is very gray and murky what contrast is it ?
low contrast
what does kVp control
what does it affect
how does kvp pertain to the body
both the quantity and quality of the xray beam
radiographic contrast
it shows how much we can absorb
what two things does kVp cause pertaining to the electrons when increased
increase in speed of electrons and the energy of the electrons applied across the tube
why is beam quantity affected when dealing with kVp
high kVp causes more interactions at the target
why is beam quality affected
each electron has more energy, resulting in a beam with greater penetrability
what ability does the xray energy have once kVp increases
penetrability
when do we need an increase of kVp
when dealing with larger patients
certain pathologies
or through casts
what percentage of increase or decrease in kvp will happen if double the mas or reduce the mas in half
if mas doubles kvp decrease by 15%
if mas is cut in half it is increase by 15%
what is the
controlling factor
and main influencing factor of
radiographic density/IR exposure
kVp
List all the factors of a High contrast image
what is the alternative name for a high contrast image
extremely white,
few shades of gray
low kvp more absoprtion
the image is
short scaled or increased contrast
list all factors for a low contrast image
what is the alternative name for a low contrast image
flat murky color
lots of shades of gray
happens with high kVp
increase of scatter radiation
the image is
decreased or long scaled contrast
use 15% rule for this:
10 mAs & 80 kVp
find the new values for short scale, increased contrast
and long scale decreased contrast
short scale
: 20 mas & 68 kvp
long scale
: 5 mas & 92 kvp
an ________ in kvp will decrease contrast and a _______ in kvp will increase contrast
increase
decrease
High contrast image has high or low kvp
low contrast image has high or low kvp
low
high
with digital and image receptor systems what is controlled through post processing
density and contrast
Author
anatomy12
ID
243739
Card Set
RAD-171 The prime Factors
Description
xray
Updated
2013-11-01T15:22:53Z
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