Rad 212 - Imaging Ii - Class 2

Front 1

The xrays that reach the IR are called ___?___

Back 1

Remnant or exit radiation

Front 2

Base

Back 2

Made of polyester for stability
Dyed blue to enhance contrast and reduce glare
Emulsion attaches with adhesive

Front 3

Supercoat

Back 3

Tough, outer layer that protects sensitive emulsion (protects the image)

Front 4

Emulsion

Back 4

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

Front 5

Silver halide crystals

Back 5

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)

Front 6

Tabular grain (T-grain)

Back 6

-Flat instead of randomly shaped as before
-More evenly dispersed
-Increases recorded detail on radiograph

Front 7

Latent image

Back 7

Image on the film after exposure but before processing

Front 8

Manifest Image

Back 8

-Image on film after processing
-Called radiographic image

Front 9

Gurney-Mott theory of latent image formation

Back 9

Describes what happens on molecular level to silver halide when exposed to xrays and light

Front 10

Latent image centers

Back 10

-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

Front 11

Two types of film

Back 11

1) Direct exposure
2) Screen film

Front 12

Direct exposure film

Back 12

-Doesn't use intensifying screen
-Cardboard cassettes
-Single emulsion
-Requires more exposure

Front 13

Screen film

Back 13

-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

Front 14

Film speed

Back 14

Degree that emulsion is sensitive to xrays or light

Front 15

Greater speed = ??

Back 15

more sensitivity

Front 16

More sensitivity = ??

Back 16

less exposure needed

Front 17

Factors that influence speed

Back 17

-Size of halide crystals
-Number of halide crystals
-Both are manipulated by manufacturers to change the speed of the film

Front 18

More and larger halide crystals = ??

Back 18

increased speed

Front 19

Film contrast

Back 19

(controlled by KVP)
-Ability of film to provide a certain level of image contrast

Front 20

Faster speed = _____ contrast

Back 20

higher contrast

Front 21

Slower speed = ______contrast

Back 21

Lower contrast

Front 22

Film latitude

Back 22

Range of exposures that would produce acceptable densities

Front 23

Wide latitude = _____ contrast

Back 23

Low contrast
(Inversely propertional)

Front 24

Spectral Sensitivity

Back 24

Refers to the color of light to which a particular film is most sensitive - blue and green in radiography

Front 25

Spectral emission

Back 25

Color of light produced by a particular intensifying screen

Front 26

Spectral matching

Back 26

Blue sensitive film has to go with blue light emitting screens and green with green

Front 27

Crossover

Back 27

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

Front 28

Crossover ________ recorded detail

Back 28

decreases recorded detail

Front 29

Some manufacturers use ________ to reduce the occurence of crossover and some add another layer called _______________

Back 29

T- grain emulsion to reduce
Added a layer to the film known as zero-crossover technology

Front 30

What is an intensifying screen?

Back 30

-Contains phosphors that convert energy to light
-Reduces exposure to patient compared to direct exposure
-Reduces recorded detail

Front 31

Phosphor is ??

Back 31

-A chemical compound that emits light when struck by radiation

Front 32

Luminescence

Back 32

Emission of light from the screen when stimulated by radiation

Front 33

Fluorescence

Back 33

(Most desired)
Phosphors emit visible light only while exposed to xrays

Front 34

Phosphorescence

Back 34

Screen lag or afterglow
Continues to emit light after the exposure has stopped (not desirable for radiography)

Front 35

Outer layer of the intensifying screen....

Back 35

-Protects the fragile phosphor material
-Made of plastic

Front 36

Phosphor layer of the intensifying screen....

Back 36

-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

Front 37

Intensifying screens - Reflecting layer

Back 37

-Magnesium oxide or titanium dioxide
-Reflects the light toward the film
-Increases the light

Front 38

Intensifying screens -
Absorbing layer

Back 38

-Light absorbing dye
-Decreases the light

Front 39

Intensifying screens -
Base

Back 39

-Farthest from film
-Polyester or cardboard
-Provides stability and support for phosphor layer

Front 40

Types of phosphors

Back 40

Calcium tungstate
Rare earth

Front 41

Calcium tungstate phosphors

Back 41

Blue

Front 42

Rare earth phosphors

Back 42

-Absorb more xrays
-Convert the xrays to visible light more efficiently
-Result in improved recorded detail when compared with calcium tungstate

Front 43

Calcium tungstate produced _______ light.

Back 43

Blue

Front 44

Rare earth screens produce _____ and ______ light

Back 44

Blue and green

Front 45

Intensification factor

Back 45

Represents the degree to which exposure factors and patient dose are reduced when intensifying screens used.
IF = Exposure without screens/exposure with screens

Front 46

Relative speed

Back 46

Results from comparing screen film systems based on the amount of light (and density) produced for a given exposure

Front 47

Par speed

Back 47

Used as standard for comparison and is assigned the relative speed of 100.

Front 48

Screen speed and density are ________ proportional.

Back 48

Directly

Front 49

mAs conversion formula for screens

Back 49

mAs1/mAs2 = RSS2/RSS1

Front 50

Phosphors used

Back 50

Calcuim tungstate
Rare earth

Front 51

Phosphor size

Back 51

Larger phosphors are faster

Front 52

Active layer thickness

Back 52

Thicker layer is faster

Front 53

Efficiency of reflective layer

Back 53

Higher efficiency makes screen faster

Front 54

Higher kVp _______ screen speed

Back 54

Increases screen speed

Front 55

Presence of yellow dye in active layer of the intensifying screen ......

Back 55

-Absorbs some of phosphor's light and reduces speed
-Increases detail

Front 56

Conversion and absorption efficiency

Back 56

-Ability of phosphors to absorb xray energy and convert it to visible light
-Higher conversion = faster screen

Front 57

Quantum mottle

Back 57

-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