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

243739

Card Set

RAD-171 The prime Factors

Description

xray

Updated

2013-11-01T15:22:53Z

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