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xray test 3
xray test 3
64
Medical
Undergraduate 1
06/30/2009

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Cards

Term
What are 2 types of AEC
Definition
phototimer and ionization chamber
Term
What does AEC stand for
Definition
Automatic Exposure Control System
Term
What are 2 types of technique charts
Definition
fixed kVp and fixed mAs
Term
Why is fixed kVp technique chart used more
Definition
most control of contrast levels
Term
Def: umbra
Definition
true image
Term
def: penumbra
Definition
fuzziness or blurriness of the outline of the image
Term
3 major classes of detail
Definition
Motion, Material, Geometric
Term
2 types of distortion
Definition
Size and Shape
Term
3 types of motion
Definition
Voluntary, involuntary and accidental
Term
3 types of material factors
Definition
Film, screen and good film/screen contact
Term
3 types of Geometric
Definition
SID, OID, and FSS
Term
What causes size distortion aka magnification
Definition
increased OID and SID
Term
What causes shape distortion
Definition
Tube angulation and body angulation when unecessary
Term
Do you get elongation or foreshortening with tube angulation
Definition
Elongation
Term
What do you get with body angulation elongation or foreshortening
Definition
foreshortening
Term
If it is impossible to position a part close the film what has to be increased
Definition
SID
Term
In order to produce a radiograph having the best detail a technician should use what type of screen speed
Definition
Slow CaWo4 (calcium tungstate)
Term
If the part to be radio-graphed is positioned so that it is not parallel to the film it will be
Definition
foreshortened
Term
The value of a small focal spot is that it helps to provide
Definition
greater detail
Term
Short exposures and immobilization of the body part are used to control
Definition
involuntary motion and sharpness
Term
what has the worst affect on detail
Definition
motion
Term
Radio-graphic detail refers to
Definition
sharpness of an image
Term
misrepresentation of the true size or shape of an object is called
Definition
distortion
Term
high speed intensifying screens allow for a short xposure time but sacrifice
Definition
image sharpness
Term
To reduce motion a technician can
Definition
communicate to the pt, use sand bags to immobilize pt and use short exposure time
Term
what is the major cause of increased magnification
Definition
increased OID
Term
Warped cassettes, worn felt in cassettes, or damaged latches cold be the cause of
Definition
poor film screen contact
Term
Grid radius effects recorded detail: true or false
Definition
false
Term
Plastic or aluminum wedge filters are examples of
Definition
compensating filters to provide uniform density
Term
what % of time a technician must make changes in the technical factors
Definition
10-25 %
Term
What is the purpose of a compensating filter
Definition
to provide uniform density
Term
What causes the most repeated radiographs in a radiology department
Definition
over exposure and under exposure
Term
What are calipers
Definition
tool used to measure pt part thickness
Term
According to the xray syllabus on radiation protection the head of the patient should be at the anode size for
Definition
thoracic spine
Term
what screen speed and fss results in the best radiographic detail
Definition
slow speed and small fss
Term
a properly designed technique chart should be based on
Definition
pt part thickness
Term
true or false penumbra is distortion
Definition
false
Term
Def: stretching of anatomy
Definition
elongation
Term
def: misrepresentations of true size and shape of anatomy on film
Definition
distortion
Term
def: main controlling factor of density
Definition
mAs
Term
def: clarity and sharpness of anatomy on a radiograph
Definition
recorded detail
Term
unsharpness around the true image
Definition
penumbra
Term
shrinking of anatomy
Definition
foreshortnening
Term
size distortion is known as
Definition
magnification
Term
main controlling factor of magnification
Definition
OID
Term
main controlling factor of contrast
Definition
kVp
Term
describe what is meant by poor film screen contact
Definition
film is not sandwhiched
Term
poor film screen contact causes what artifacts
Definition
blurry white spots
Term
the central ray is not directed to the center of the film what kind of distortion would u get
Definition
shape
Term
Recorded detail can be measured and is expressed as:
Definition
resolution
Term
A resolution pattern will do what:
Definition
measure and record line pairs per mm
Term
what is recorded detail defined as
Definition
accuracy of structural lines recorded
Term
the relationship between focal spot size and distance results in
Definition
geometric unsharpness
Term
increasing SID will
Definition
increase recorded detail
Term
Decreasing OID will:
Definition
increased recorded detail
Term
the ability of the imaging system to distinguish between 2 adjacent structures defines
Definition
resolution
Term
what is the equation for making your own chart
Definition
body in CM x 2 + 30 and has to be over 44 kVp
Term
what 2 conditions must be met before technique charts can be affective?
Definition
xray equip. must be calibrated and image processing must be consistent through department
Term
def:kVp value that is high enough to ensure penetration of the part but not too high to diminish radiographic detail
Definition
optimal kVp
Term
Def: pre-established guidelines used to select standardized exposure factors
Definition
exposure technique chart
Term
what is the primary patient factor that determines the selection of exposure factors
Definition
pt part thickness
Term
what is the primary goal of exposure technique charts
Definition
consistently produce quality images
Term
what is an advantage of a fixed kVp technique
Definition
reduces pt exposure
Term
what is disadvantage of variable kVp technique chart
Definition
increases heat load on xray tube
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