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60 Cards in this Set

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  • Back
Grids
increase contrast
Short Scale Contrast
70 kvp and under
Grid Ratio
ratio between height & distance of lead strips
Fogging
main cause secondary
radiation or scatter
Air Gap
eliminates need for grid
Contrast
makes detail clear - visible
Chimicals too low
developer will show low contrast
Influencing Factors of Contrast
film, developer, grid, SID
Latent Image
becomes visible after exposure
Manifest
becomes visible after developing
Collimation
reduction of radiation will increase contrast
X-Ray Table
grid lines run same direction as the table
Minimum total filtration
2.5 mm aluminum or equivalent
Grids have?
lead strips, aluminum, interspaces - cardboard fiber - poly plastic
Contrast controlled by?
kvp (main control) and mAs
Grid - non grid
decrease technique
Non-grid to Grid
increase technique
When you increase kVp you?
decrease contrast
Purpose of conpensating filter (added filter)?
produce a more uniformity dense radiograph
Smaller exposure field?
increase contrast
When hight kVp affects contrast
reduce contrast
Grids are made of:
polyester plastic
fiber (cardboard)
aluminum
Collimator check for?
size accuracy
Fog increases when?
increased thickness
Differential Absorption
bone and soft tissue
What absorbs more radiation?
bone
Low kVP will result in?
short scale contrast
Subject contrast?
patient
Grid Frequency
the number of lead strips per cm
Types of Grids
stationary and moving grid
Best for grid clean up?
the higher the number the better the clean up best 16:1
Grid ratio most latitude
12:1
Secondary Factor of Contrast
mAs
Half Value Layer
the thickness or amount of aluminum necessary to reduce the intensity of the x-ray beam by half
Types of Collimators
rectagular (most common)
cones
cylinders
extension cylinders
diaphragm
Compression Filters
body part when the node heel effect is not enought (provide uniform density on the film)
California Regulations
collimate the beam to the area of clinical interest
Main purpose of collimation?
limits the x-ray beam to the area of clinical interest
Proper use of a collimator
reduces the amount of secondary radiation produced
Grid located between?
patient and x-ray film
Grid lines appear when
bucky is not turned on
Common type of beam restrictor?
variable rectangular
Secondary radation/scatter
when x-ray beam penetrates an object and scatters in all directions the effect is called
Total Filtration
added filtration (2 mm) + inherent (.5 mm aluminum)
Main causes of fog
radiation
Reduce fogging by?
use better collimation
Inherent Filter consist of?
oil and glass envelope & glass window
Which contrast scale will produce consistent radiograph?
Long Scale
Radiopaque tissue
shows a lighter areas on a radiograph to make visible
Absorption/Attenuation
structures of different densities absorb/attenute the x-ray beam differently (bone-tissue-muscle)
Inherent filters
built into machine
Added filters
that which is addes
Filtration removes?
photons of long wavelengths hardening the x-ray beam and producing short or long scale
Collimation regulates?
amount of scatter radiation produces improving contrast
Types of Grid Cut Off
off center
off focus
off angle
upside down
crooked
incorrect SID (grid focus)
Phototimer
automatically terminates exposure when adequate Radiographic Density has been achieved
Four Prime Factors of Radiography
mAs
kV
SID
Cut the mAs in 1/2
a 15% in kVp is equivalent to a 50% increase in density on the radiograph therefore, in order to maintain the same radiographic density, every 15% increase in kVp must be accompanied by a 50% reduction in mAs
Double the mAs
a 15% decrease in kVp is equivalent to a 50% reduction in the density on the radiograph therefore, in order to maintain the same radiographic density: every 15% reduction in kVp must be accompied by a 50% increase in mAs
Rule of Thumb
mAs-Distance Formula
when the distance is cut exactly in half one-fourth (1/4) of the original mAs is used to maintain the proper radiographic density.

If the SID is doubled then four (4) times the original mAs is necessary to maintain the proper radiographic density.