Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/57

Click to flip

57 Cards in this Set

  • Front
  • Back
The xrays that reach the IR are called ___?___
Remnant or exit radiation
Base
Made of polyester for stability
Dyed blue to enhance contrast and reduce glare
Emulsion attaches with adhesive
Supercoat
Tough, outer layer that protects sensitive emulsion (protects the image)
Emulsion
Adhered to base with adhesive
Made of light and radiation sensitive materials suspended in gelatin
On both sides with double emulsion-single sided with single emulsion film
Silver halide crystals
Silver halide crystals
Amount and size of crystals determine speed of film
Assumed that 90-99% of solution is silver bromide (AgBr) and 1-10% is silver iodide (AgI)
Tabular grain (T-grain)
-Flat instead of randomly shaped as before
-More evenly dispersed
-Increases recorded detail on radiograph
Latent image
Image on the film after exposure but before processing
Manifest Image
-Image on film after processing
-Called radiographic image
Gurney-Mott theory of latent image formation
Describes what happens on molecular level to silver halide when exposed to xrays and light
Latent image centers
-Several sensitivity specks with many silver ions attracted to them
-Appear as radiographic density on the final image
-Must contain 3 sensitivity specks with 3 silver atoms each
-More exposure to film = more metallic silver is apparent as density on the image
Two types of film
1) Direct exposure
2) Screen film
Direct exposure film
-Doesn't use intensifying screen
-Cardboard cassettes
-Single emulsion
-Requires more exposure
Screen film
-Made to be used with one or two intensifying screens
-Compared to direct exposure film, this is more sensitive to light and less to xrays
-Emulsion layers are thinner and require less processing time
Film speed
Degree that emulsion is sensitive to xrays or light
Greater speed = ??
more sensitivity
More sensitivity = ??
less exposure needed
Factors that influence speed
-Size of halide crystals
-Number of halide crystals
-Both are manipulated by manufacturers to change the speed of the film
More and larger halide crystals = ??
increased speed
Film contrast
(controlled by KVP)
-Ability of film to provide a certain level of image contrast
Faster speed = _____ contrast
higher contrast
Slower speed = ______contrast
Lower contrast
Film latitude
Range of exposures that would produce acceptable densities
Wide latitude = _____ contrast
Low contrast
(Inversely propertional)
Spectral Sensitivity
Refers to the color of light to which a particular film is most sensitive - blue and green in radiography
Spectral emission
Color of light produced by a particular intensifying screen
Spectral matching
Blue sensitive film has to go with blue light emitting screens and green with green
Crossover
Light that is produced by the intensifying screen then "crosses over" the base layer and exposes the other side also
-Unique to double emulsion film with intensifying screen
Crossover ________ recorded detail
decreases recorded detail
Some manufacturers use ________ to reduce the occurence of crossover and some add another layer called _______________
T- grain emulsion to reduce
Added a layer to the film known as zero-crossover technology
What is an intensifying screen?
-Contains phosphors that convert energy to light
-Reduces exposure to patient compared to direct exposure
-Reduces recorded detail
Phosphor is ??
-A chemical compound that emits light when struck by radiation
Luminescence
Emission of light from the screen when stimulated by radiation
Fluorescence
(Most desired)
Phosphors emit visible light only while exposed to xrays
Phosphorescence
Screen lag or afterglow
Continues to emit light after the exposure has stopped (not desirable for radiography)
Outer layer of the intensifying screen....
-Protects the fragile phosphor material
-Made of plastic
Phosphor layer of the intensifying screen....
-Active layer, most important
-Contains phosphor material that absorbs the transmitted xrays and converts them to visible light
-Sometimes light absorbing dye is added to reduce # of xrays striking the film
Intensifying screens - Reflecting layer
-Magnesium oxide or titanium dioxide
-Reflects the light toward the film
-Increases the light
Intensifying screens -
Absorbing layer
-Light absorbing dye
-Decreases the light
Intensifying screens -
Base
-Farthest from film
-Polyester or cardboard
-Provides stability and support for phosphor layer
Types of phosphors
Calcium tungstate
Rare earth
Calcium tungstate phosphors
Blue
Rare earth phosphors
-Absorb more xrays
-Convert the xrays to visible light more efficiently
-Result in improved recorded detail when compared with calcium tungstate
Calcium tungstate produced _______ light.
Blue
Rare earth screens produce _____ and ______ light
Blue and green
Intensification factor
Represents the degree to which exposure factors and patient dose are reduced when intensifying screens used.
IF = Exposure without screens/exposure with screens
Relative speed
Results from comparing screen film systems based on the amount of light (and density) produced for a given exposure
Par speed
Used as standard for comparison and is assigned the relative speed of 100.
Screen speed and density are ________ proportional.
Directly
mAs conversion formula for screens
mAs1/mAs2 = RSS2/RSS1
Phosphors used
Calcuim tungstate
Rare earth
Phosphor size
Larger phosphors are faster
Active layer thickness
Thicker layer is faster
Efficiency of reflective layer
Higher efficiency makes screen faster
Higher kVp _______ screen speed
Increases screen speed
Presence of yellow dye in active layer of the intensifying screen ......
-Absorbs some of phosphor's light and reduces speed
-Increases detail
Conversion and absorption efficiency
-Ability of phosphors to absorb xray energy and convert it to visible light
-Higher conversion = faster screen
Quantum mottle
-Caused by film not receiving enough photons
-Images appears grainy
-Problem with very fast film/screen systems that require very little exposure
-mAs should be increased and speed decreased