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74 Cards in this Set
- Front
- Back
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Monochromatic
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Sensitive to blue or blue violet
Amber colored filter (Whatten 63) |
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Orthocromatic
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Sensitive to blue or green
Red Filter (GSl/GDX) |
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Panchromatic
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Sensitive to all colors
Requires total darkness |
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How are films packaged?
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sealed in metal foil & paper to protect from light and moisture
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How are films stored?
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in cool, dry place. (50-70 deg)
65 to 68 deg. is ideal 40 to 60% humidity is ideal |
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Pressure effects on film
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causes pressure artifacts. Must store like books and not on top of each other.
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Films must be stored for how long?
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5 to 7 yrs. Unless child, must store until 18 yrs.
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Why should film not be used after exp. dt.?
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loss of contrast, speed and causes fog
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What is the protective geletin layer on the top of film?
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supercoat
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What adhears emulsion to the base on film?
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Adhesive layer
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Film base is made of?
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polyester plastic
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Film is Clear but has a blue tint, why?
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to help with eye strain, and increase contrast
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What is film emulsion
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a homogenous mix of geletin and halides (ag br and ag I)
It's the material which the x-rays or light interact with and transfer info |
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Silver Halides are a crystal lattice structure with imperfections called?
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sensitivity specks (electron traps of AgS)
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Differences in film speed, resolution, contrast, etc are determined by?
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concentration of crystals, distribution and mix, # of sensitivity specks, crystal size, crystal shape and emulsion thickness
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What is the MOST important determinate of speed (in reference to silver halides)?
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Concentration of crystals in emulsion
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What is a Latent image?
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an invisible change induced by the silver halide crystals by interaction with light or the remnant radiation exiting patient and incident on film.
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Formation of a latent img is also known as the?
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Gurney-Mott Theory
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Direct Exposure Film
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outdated, requires more exposure and development time due to thicker emulsion, used w/out intensifying screens. Used in dental radiography.
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Double-Emulsion film
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typically used with 2 intensifying screens. Emulsion layer on both sides of the base and a layer of super coat over each coating
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single-emulsion film
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1 emulsion layer used with 1 intensifying screen, used in many modalities and has anti curl layer which makes it different from double-emulsion
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Screens and film must be compatible, this is called?
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Spectral matching
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Intensifying screens have 4 layers, called?
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protective layer, phosphor layer, reflecting layer and base
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What are advantages of intensifying screens?
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decreased patient exposure, 90-99% of total amount of energy the film is exposed is light
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disadvantage of intensifying screen?
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decreased recorded detail
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Intensifying Screens - types of phosphors?
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-Calcium tungstate (blue light)
-Rare earth (ultraviolet/blue, green or blue light) *better of the 2* |
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Examples of Rare Earth Phosphors
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Lanthanum oxybromide
Yttrium Tantalate Gadolinium Oxysulfide |
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Intensifying Screen Factors
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Absorption efficiency, conversion efficiency, thickness of phosphor layer, size of phosphor crystal, presence of reflecting layer and dye in phosphor layer
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Film characterisitc curve is aka?
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Hurter-Driffield Sensitometric curve (H & D Curve)
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What does the H&D Curve do?
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plots the OD (optical density) to the radiation exposure
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what is the purpose of the H & D/Film Characteristic Curve?
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indicate the degree of contrast or different densities that a film can display using a range of exposures
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Film Characteristic Curve shows what three main things?
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Film Speed
Film Latitude Film contrast |
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Film Speed (h&d curve)
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Rate of exposure
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Film Latitude (h&d curve)
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Margin of error for technique
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Film contrast (h&d curve)
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slope of the line
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What are the three portions of the film characteristic curve?
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Toe, Shoulder and slope/straight line portion
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Portion of Film Characteristic Curve that shows underexposure?
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Toe
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Portion of Film Characteristic Curve that shows overexposure?
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Shoulder
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Portion of Film Characteristic Curve that Image contrast (density) will be acceptable in the?
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slope
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What is film contrast?
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built in ability to display a range of tones (optical density difference)
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High contrast film accentuates more?
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black and white areas
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Low-Contrast shows more shades of?
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gray
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What is Contrast Latitude?
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the visible difference between any two selected areas of density levels within the radiographic image
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What is scale of contrast?
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number of densities visible
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long scale
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long range, many shades of gray, low contrast
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short scale
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short range, few shades of gray, high contrast
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Film speed is?
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relative ability of film emulsion to respond to radiation
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Films with high speed require ________ exposure than films with low speeds
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less
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What 2 factors affect film speed?
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# of silver halides present and size of silver halides present
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Film Latitude is?
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the built in ability of film to record a long range density levels on the radiograph
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Film latitude and film contrast depend upon what?
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the sensitometric properties of the film and processing conditions and are determind from the H & D curve
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Exposure Latitude is?
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range of exposure factors which will produce a diagnostic radiograph
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Four steps of processing?
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Developer
Fixer Wash Dryer |
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Function of the developer?
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Convert latent image into visible image
Developer is alkaline |
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optimum temp for developer?
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68-72 but may be as high as 85-105.
most commom is 92-96 |
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Reducing agent
(developer chemicals) |
provides electrons to silver ions, reducing them to black metallic silver
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preservative
(developer chemicals) |
prolongs developer life by controlling oxidation by air
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accelerator/activator/gel sweller
(developer chemicals) |
causes gel swell to allow developer to penetrate
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restrainer
(developer chemicals) |
restrains reducing aagent from reducing unexposed crystals
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hardener
(developer chemicals) |
controls swelling and softening of emulsion. If it swells too much, wont transport properly, films could be damp
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Developer replenisher compensates for?
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decreased chemical activity & loss of volume
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Fixer
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makes the image permanent, hardens emulsion
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Clearing Agent
(fixer chemicals) |
removes unexposed silver halide crystals from emulsion
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acidifier
(fixer chemicals) |
neutralizes alkaline developer, stopping development
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hardener
(fixer chemicals) |
accelerates the emulsion shrinking process and causes emulsion to harden
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preservative
(fixer chemicals) |
prolongs life of clearing agent by dissolving silver out of fixer
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If unexposed crystals weren't removed what would happen to the films?
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they would have increased density
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if films are tacky and damp what is not working?
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the hardener
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if film is fogged what is not working?
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clearing agent
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if films are green or milky what is not working?
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developer is retained in fixer
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Wash
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washes away remaining chemistry, temp is five degrees below dev. temp.
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What will happen to films if wash is inadequate?
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films will turn brown with time
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Dry
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Dries film, seals supercoat and hardens emulsion
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steps of the automatic processor system
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Transport, replenishment, recirculation, temp. control and dryer
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