Film Screen Flashcards
Radiographic Processing
Chemical tanks, roller transport system and dryer
Automatic Processing
What turns the image permanently visible or a manifest image?
Exposure of the silver bromide crystals in the emulsion by light or x-ray photons creates the latent image and initiates the conversion process
Types of phosphors
- most common- some elements from rare earth group
- Rare earth elements (57-71 atomic # on periodic table)
- Rare earth absorbs more x-rays, then converts to visible light more efficiently
Operate by process of luminescence- emission of light from screen when stimulated by radiation
- Florescence ability to emit visible light
* Phosphorescence screen phosphors continue to emit light after exposure ends, screen lag/after glow
The protective layer is made up of what and protects what?
plastic
fragile phosphor
What is the most important layer in the intensifying screens?
Phosphor or active layer- absorbs transmitted x-rays and converts them to visible light
What layer reflects or absorb light
Reflecting or absorbing layer
The bottom layer of the intensifying screens is what and made up of what?
Base
polyester or cardboard
provides support and stability for phosphor layer
(refer to Pg. 115 box 5.3 in fauber)
Intensifying Screens
- placed in cassettes
- front screen tube; opposite is back screen
- double emulsion exposed to twice as much light as single emulsion due to both sides being exposed
- single screen is mounted as back screen opposite the tube side
Ability of radiographic film to provide level of image contrast
Contrast
(high- more black and white areas)
(low- more shades of grey)
What are the two categories of spectral sensitivity
blue sensitive and green sensitive
Refers to color of light produced by the intensifying screen, blue and green light emitting
Spectral Emission
Refers to correct match of film and screens
Spectral Matching
Failure to match will result in what?
Suboptimal density
What do intensifying screens do?
Convert x-rays images into light
What chemical compound emits visible light when struck by radiation
phosphor
Purpose of screens-
reduce radiation dose to patient - less mAs
______ _______ is coated on both sides of the base with layer of supercoat and is used with two intensifying screens
Double Emulsion
______ ________ coated with only one layer; used with single intensifying screen used for mammography?
Single Emulsion
Characteristics of Single Emulsion
- Anticurl/antihalation layer is colored backing on single emulsion that prevents curling and halation
- halation is (light reflected back to expose the emulsion a second time)
- light reflected back comes from intensifying screen
Sensitivity or speed affected by silver halide crystals in the emulsion both number and size of crystals;
As they increase film speed increases
Film Characteristics
manufactures can manipulate speed with changes in the number and size of the crystals
Image that exists on the film after exposure and processing- typically called radiographic image
Manifest Image
What are the two general types of film
Direct exposure and screen film
Characteristics of Direct exposure
- non screen film
- single emulsion thicker than screen film requires more development time
- requires more exposure may need manual processing, used for oral/dental imaging
- Ready packs of radiation therapy film for port film localization may/may not be placed in cardboard cassette
Characteristics of Scatter Film
- Used with one or two intensifying screens
- more sensitive to light and less sensitive to radiation
- emulsion layers thinner than direct exposure and require less development
- requires less radiation exposure
- can have single- double emulsion
What effects the quality of the film?
Kvp
What effects the quantity of the film?
mAs
Film Screen Combination-
- film screen-systems are classified by RS factor
- RS factor speed range from 50-800
- extremity film screen- 100
- routine high speed- 400
Radiographic film used in a cassette with intensifying screens is the most common image receptor today
Double emulsion
What does film record
the image produced by intensifying screens
The rigid, light tight container that holds the screen and film in close contact
Cassette
What are the layers of the film
Outside- supercoat, durable protective layer damage to sensitive emulsion layer
Next layer- emulsion radiation and light sensitive layer- consist of silver halide crystals suspended in gelatin
Final Layer
What does the final layer in the base contain
a blue dye tint to reduce eye strain when viewing finished radiograph
Image which exists on film after film has been exposed and before processing
latent image
Silver Halide
Material that is sensitive to radiation and light, silver bromide (AgBr) and silver iodide make up the emulsion layer of the film
AgBr
90-99%
Agl
1-10%
Exact formulation Proprietary Information
Business only- Super Secrete
