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168 Cards in this Set
- Front
- Back
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X-ray Film Composition
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Base, Adhesive, Emulsion, Supercoat
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Base
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- originally glass was used (WWI)
- now polyester plastic - coated w/ light-absorbing dye to prevent crossover effect |
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What colors is the base tinted with?
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Blue or green
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Adhesive
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- thin coating applied to both side of film base on double emulsion, 1 side for single emulsion
- prevents bubbles or other distortion when film is bent during processing/handling - keeps film error & artifact free for longer amounts of time |
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Emulsion
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- composed of gelatin & crystals
- gelatin is a non-reactive medium through which chemicals can diffuse to reach silver halide ions - silver halide crystals are suspended within gelatin to allow them to distribute evenly over surface |
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Silver Halide Crystals
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- 95% silver bromide, remainder is silver iodide & silver chloride
- can be described as "silver iodobromide" - photosensitive; suspended in emulsion |
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Supercoat
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Layer of hard, protective gelatin designed to prevent the soft emulsion underneath from being damaged
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What are the 4 stages of manufacturing?
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Crystal production, ripening, mixing, & coating
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How are crystals formed?
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- By combining silver nitrate & potassium bromide in the presence of gelatin
- completed in total darkness - silver bromide precipitates out & potassium nitrate is washed away as byproduct |
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What shape are the crystals?
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Flat & roughly triangular; helps reduce crossover effect
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What are the crystals made up of?
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- Ag, Br, & I atoms
- 1 mm^3 of emulsion will contain over 1/2 billion halide crystals |
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Sensitivity Specks
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- Must be present to provide film sensitivity
- usually gold-silver sulfide added to the silver halide crystals - serve as electrodes to attract the free silver ions |
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Ripening
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- Period during which silver halides are allowed to grow
- Longer the ripening period, the larger the crystals & the more sensitive the emulsion |
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Mixing
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- shredded emulsion is melted to properly sensitize crystals
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What is added to melted emulsion?
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1) Hardeners to prevent trauma
2) Bactericides & fungicides to inhibit growth 3) Antifogging agents 4) Colored dyes to improve sensitivity |
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Panchromatic Film
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Sensitive to all colors
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Orthochromatic Film
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Sensitive to colors other than red spectrum (i.e. blue or green)
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Latent Image
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Unseen change in atomic structure of crystal lattice that, once developed, produces a visible image
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Manifest Image
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The visible image seen when a latent image is processed
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Gurney-Mott Theory
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- When incident photon interacts with 1 halide, it knocks out an electron
- Ejected electron is attracted to the sensitivity speck which creates a negative charge - Speck attracts positively charge free silver ion; continues until a clump of silver atoms rests @ speck |
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How many silver atoms must be deposited to see an image?
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3 silver atoms
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Direct-Exposure/Non-Screen Film
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- used to produce FINE DETAIL
- single emulsion - very fine grains of silver halide crystals w/ greater silver content - requires more radiation to produce image; increased patient dose |
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What is Direct-Exposure/Non-Screen Film used for?
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Dental x-rays, degenerative bone disease, healed fracture surveys, nondestructive testing radiography,
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Intensifying-Screen Film
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- works w/ intensifying screens that are part of cassette
- comes in a variety of speeds, contrast ranges, latitudes, & resolutions |
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Larger Crystals & Thicker Emulsions = ?
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-Lots of shades of gray, wider latitude, less resolution
- good for abdomen x-rays, bad for hand x-rays |
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Intensifying-Screen Film - Single Emulsion
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- has a notch on film edge which should be placed in lower left corner of cassette each time
- emulsion side should be loaded toward intensifying screen - some have gelatin to prevent shrinking & curling during processing |
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Intensifying-Screen Film - Double Emulsion
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- makes screen film FASTER which produces more density w/ less exposure
- with the increased sensitivity there's less mAs used |
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Special Applications Film
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- most are single emulsion
- different types of film are sensitive to different types of light |
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What type of light is laser-exposed film sensitive to?
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Red laser light used by laser format cameras
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What type of light is cathode ray tube imaging film sensitive to?
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Light emitted by a CRT
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Special Applications Film - Duplication Film
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- produces a copy of original film
- pre-exposed to permit the film to duplicate original image - sensitive to UV light - single emulsion - once Dmax is applied, future exposure will become lighter w/ more exposure - density is dependent on amount of light exposure time |
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Solarization Effect
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- exposing halide film to light
- light exposure to film will cause film to eventually reach maximum density (Dmax) - further exposure causes a reduction in density |
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Special Applications Film - Subtraction Film
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- fine-grain, non-tinted
- produces a negative image of a preliminary scout angiographic (displays bone as black instead of white) |
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Special Applications Film - Cineradiography Film
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- similar to 35 mm film used in single lens reflex cameras
- sensitive to GREEN LIGHT - used for cardiac catheterization angiography - fine detail - high patient dose required |
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Special Applications Film - Fluoroscopic Spot Film
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- similar to cineradiographic film
- sensitive to GREEN LIGHT - 70-150 mm sizes used |
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Crossover Effect
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- light from 1 intensifying screen crosses over through film base & activates opposite emulsion causing unwanted density & blurring of image
- occurs w/ double emulsion film - Remedy: films are coated w/ special substance to prevent light crossover |
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Halation
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- caused by light being reflected from air/film base on the back of single emulsion film
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Remedy for Halation
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- anti-halation coating may be applied to emulsion side
- coating designed to absorb the light coming in through emulsion & prevent backscatter, visible light, or reflected light from degrading image - coating increases patient dose, typically only used in extremity cassettes - emulsion side will be "Dull", non-emulsion side will be "shiny" |
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How is the anti-halation coating removed?
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By the processing chemicals so light can be transmitted through film for viewing
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How long are x-ray images usually kept in a facility?
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Usually 7 years, mammography images kept for patient's lifetime
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How should film be stored?
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- used before expiration date
- stored at 68 degrees F; brought to room temp before use - humidity should be between 30-60% - store film on edge, not flat |
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Film Storage - Automated Systems
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- will load film before exposure, transports film for processing after exposure
- uses a film magazine |
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What's a film magazine?
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Used to feed single film from storage unit to a location between 2 intensifying screens in a cassette
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Film Storage - Daylight Systems
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- cassette loading system that can be operated in full light instead of a darkroom
- light-proof loading & unloading units |
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Film Identification
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Should always include patient name, patient ID, date, & institution name
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Artifacts
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Undesirable densities or blemishes on a radiograph
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Artifacts - Exposure/Equipment
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- can have a bad cassette (multiple films in cassette, warped cassette, scratched, foreign objects)
- grid cutoff - bucky misalignment |
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Artifacts - Patient
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- motion, dressing instructions
- immobilizers (spine boards, C-collars) - tubing - positioning aids |
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Artifacts - Processing
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- chemical fog (curtain effect)
- transport artifacts (roller marks, guide-shoe marks, wet pressure sensitization) - fixer retention |
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Artifacts - Handling
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- kink/pressure marks (bending, fingernail marks, bad cassette loading)
- static (low humidity) - storage artifacts |
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What's the primary purpose of film developing?
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To deposit enough black metallic silver at the latent image sites to create a visible permanent image
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What happens when film enters the developer?
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- emulsion swells, which allows developer to access the silver halide crystal lattice
- reducing agents convert the silver ions to black metallic silver to produce manifest image - film no longer light sensitive |
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How much silver is required to create a visible density? (minimum amount)
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3 atoms of silver attached to a sensitivity speck
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Agents within the Developer
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Activator, reducing agents, restrainer, preservative, hardener, & solvent
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Activator - Developer
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- maintains alkalinity of the solution (can be neutralized w/ fixer or H2O)
- sodium carbonate - assists reducers in reaching silver halides by causing gelatin to swell & become penetrable |
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Oxidation
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process of reducing agents giving up electrons to neutralize the positive silver ions
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Reduction
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when a silver halide crystal takes 1 of those electrons freed up by oxidation & is changed to black metallic silver
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As oxidation/reduction occurs, what color will the developer solution change to?
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From light yellow to deep amber-brown to thick rust-red
Will reduce developing solution as process occurs |
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Reducing agents supply ____________ to silver ions attached to the sensitivity specks
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Electrons
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Phenidone (P developer)
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- quickly reduces silver to metallic silver & works only in areas of minimal exposure
- cannot reduce areas of heavy exposure - enhances fine detail & subtle changes of gray - controls "toe" portion of H&D curve |
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Hydroquinone (Q developer)
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- slowly reduces silver & produces heavy density
- works in areas of high exposure - controls "shoulder" portion of H&D curve |
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P & Q Together
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- both are needed to get proper diagnostic image
- works synergistically (sum of them equals greater ability) - known as "superadditivity" |
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Restrainer - Developer Solution
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- potassium bromide
- added to developer solution to restrain reducing action to crystals w/ sensitivity speck gates (ex. putting brakes on a car) |
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Preservative - Developer Solution
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- sodium sulfite
- decreases oxidation of the reducing agents when they're combined w/ air |
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Hardener - Developer Solution
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- glutaraldehyde
- controls swelling of gelatin to prevent scratches & abrasions to emulsion during processing - maintains uniform film thickness |
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What does insufficient hardener cause?
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- films to deposit gelatin on processor rollers
- films to exit the processor w/ moist, softened surfaces |
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What does excessive hardener cause?
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- emulsion can harden prematurely, which prevents chemical interactions w/ silver halides
- traps moisture in gelatin |
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Solvent - Developer Solution
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- water
- all processor chemicals are mixed with & suspended in water |
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Developer Depletion
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- becomes depleted when reducing agents lose their ability to provide electrons to ionic silver
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Contamination
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- 0.1% (10 mL per 2.5 gal) of fixer within developer tank will contaminate it
- most common cause = removing/replacing crossover racks |
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Agents within the Fixer
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activator, clearing agent, preservative, hardener, solvent (H2O)
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Activator - Fixer Solution
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- acetic acid
- maintains acidity of fixing solution to enhance function of clearing agent - acts as "stop" bath to stop reducing agents' function - developer is alkaline, fixer is acidic |
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Clearing Agent - Fixer Solution
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- ammonium thiosulfate (hypo)
- primary agent of fixer solution - bonds w/ unexposed silver halides & removes them from emulsion - if isn't allowed to work completely, it will have gray milky appearance |
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Preservative - Fixer Solution
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- sodium sulfite
- allows clearing agent to remove more non-exposed silver from emulsion - dissolves silver from clearing agent |
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Hardener - Fixer Solution
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- aluminum salts (potassium a., a. chloride, chromium a.)
- serves same purpose as hardener in the developer |
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Fixer Depletion
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- occurs when solution becomes saturated w/ silver ions
- requires longer clearing time |
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Are the chemicals used in developer & fixer hazardous?
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Yes; hydroquinone, preservative, & activator have pH of 12; glutaraldehyde is same agent used for tanning leather
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Washing
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- removes any remaining developer & fixer solutions
- water temp should be slightly lower than developer/fixer solutions |
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Drying
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- forcing hot air against both sides of film
- sets final hardening to emulsion & seals supercoat - temp ranges from 120-150 F |
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Who introduced the first automatic processor?
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Eastman Kodak in 1957
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Parts of Auto Processing System
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Transport, dryer, replenishment, circulation, & temperature control
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Transport System
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- designed to move film through all sections of processor
- time of film submersion is coordinated w/ aspects of processing chemicals - transport racks consist of 3 pairs of rollers under constant tension |
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Turnaround Rollers
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Used to bend the film at the bottom & top of transport racks
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Entrance Rollers
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Start film traveling from feed tray down into developer solution
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Crossover Networks
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Bend & turn film when it reaches end of roller system for each tank
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Guide Shoes
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Used to help keep proper alignment of film when passing from roller to roller
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Drive System
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- single electro-motor drives entire series of rollers
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Dryer System
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- final stage of processing
- dries emulsion to allow long-term storage of film - film exits processor damp = fixer depletion, lack of hardener, or wash tank needing fresh water |
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Replenishment System
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- automatic processors replenish developer & fixer solution to prevent chemical depletion
- film enters processor & replenishment pump starts simultaneously - typical rate = 4-5 mL of fluid per inch of film - after replenishing, allow processor to "season" for 15-20 min |
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Volume Replenishment
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- used for high-volume processing
- activated by film micro-switch or infrared sensor |
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Flood Replenishment
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- used for low volume units where films enter processor @ irregular intervals
- controlled by time mechanism |
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Circulation System
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- designed to stabilize temps, agitate solutions, mix chemistry, & filter solutions
- separate circulation systems for each part - draw chemistry from bottom ends of tanks & pump it into the upper level |
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Temperature Control System
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- maintains temp of all 3 solutions
- 0.5 degree fluctuation of temp can have a visible effect on quality of processed films - at 92-96 F, developer immersion time is 20-22 sec - at 68 F, immersion time is 4-8 min (*ideal temp*) |
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Feeding the Processor
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- films should be fed in w/ short axis of film entering first, long axis parallel w/ rollers
- films should be sent into processor using opposite sides of feed tray for every other film - automatic processor regulates replenishment - audible noise & safelight feed mechanisms to avoid film overlap |
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Darkroom Components
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Single/Revolving Door, safelights, & passbox
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Safelights
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- film designed to be insensitive to orange-red light
- low intensity used (7-15 watts), large distance away |
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Passbox
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- lightproof container allowing only 1 side of doors to open at a time, preventing exposure to undeveloped film
- most have 2 sides |
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How is a darkroom designed when a large processor is involved?
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- place outside of room, have feed tray inside
- minimizes space requirements - allows for quicker viewing of images |
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Where should film bins be located?
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Under the cassette loading center
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Why is good ventilation important?
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Because (Especially if processor is in room) chemicals aren't good for human inhalation
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What humidity is ideal?
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30-60%
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Silver Recovery Systems
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- method of removing silver from fixer solution (earn some money [10% of the expense of film]), government has regulations about how many toxins you can pour down drain)
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Fixer can accumulate silver at a rate of _______________
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100 mg/m^2 of film processed
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How much of unused silver from film is deposited in fixer?
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50%
- can reuse silver if it comes into contact w/ electrons, make more black metallic |
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Types of Silver Recovery Systems
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Electrolytic silver recovery system, metallic replacement, chemical precipitation, & resin
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Electrolytic Silver Recovery System
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- most often used
- current passes from cathode to anode through fixer, ionized silver in fixer solution is attracted to cathode, metallic silver attaches to plate as electrons move - units = recovery capacity - shouldn't be run when processor hasn't been used for awhile |
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Storage of Films
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- average = 5-7 years
- peds = 3 years after age 21 - mammo = 5-7 years after patient deceased |
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How should Films be Stored?
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- "on edge" not stacked on top of each other
- 60% humidity, 70 F temp - recycle processed films to recover silver |
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Soft Tissue Radiography
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- low subject contrast
- tissues have similar atomic numbers |
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Robert Egan, 1950s
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- used low kVp, high mAs, direct film exposure (no intensifying screens)
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Xeromammography 1970s
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- lower dose than 1950s
- higher kVp, edge enhancement |
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2000
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1st digital mammography approved by FDA
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Mammography Quality Standards Act (MQSA) 1991
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- standardized the equipment & quality control testing
- took effect in 1994 |
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Are mature breasts as sensitive to radiation as immature breasts?
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No
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Glandular dose should not exceed ____________________ without grid and __________________ with the grid.
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100 mrad/image; 300 mrad/image
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What do mammography machines have to have?
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- molybdenum target & filter (or rhodium)
- tungsten target w/ Mo Rh, Au, or Al filter - grid, AEC, compression - high frequency generators - microfocus tube (under 0.1 mm - 0.3 mm) SID = 60-80 cm |
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Screen-film combination minimum resolution up to ______________ when a high contrast resolution bar test pattern is oriented w/ bars PERPENDICULAR to anode-cathode axis
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11 line-pairs/mm
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Screen-film combination minimum resolution up to ______________ when a high contrast resolution bar test pattern is oriented w/ bars PARALLEL to anode-cathode axis
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13 line-pairs/mm
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How much kVp is needed to penetrate breast tissue?
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17-24 kVp, most machines used 23-32 kVp
Rhodium #45 about 20-23 keV (used for larger or denser breasts) |
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Focal Spot for Mammo
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- circular shape, most have approx. 23 degree anode angle & 6 degree tube tilt
- high spatial resolution (looking for microcalcifications) - 0.3 mm large & 0.1 mm small - tube tilt makes CR parallel to chest wall |
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What type of x-rays are used for mammo?
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Low dosage; only want to filter the x-rays that are so small we know they won't go through
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Filtration
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Filters of the same materiel as the target, allows characteristic radiation to penetrate & suppresses higher/lower energy Bremsstralung
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Heel Effect w/ Mammo
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- short SID makes heel-effect more apparent
- angling tube allows less tube tilt & smaller apparent focal spot |
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What does compression do?
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lowers OID, higher SOD, higher resolution, less scatter & dose, immobilization
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Automatic Exposure Control w/ Mammo
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- post-exposure, counts how many x-rays have penetrated
- have filters that enable them to discern image quality - have to have AEC cell completely covered by tissue |
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Mammography Magnification
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- up to 2x
- effective focal spot < or equal to 0.1 mm |
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Biased Focusing
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- negative voltage applied to focusing cup reduces size of electron stream
- patient dose doubled (less SOD) - used for microcalcifications & small lesions |
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Why don't we need a grid when we use magnification?
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Increased OID
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Screen-Film Mammo
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- single emulsion
- higher contrast especially in toe region - film/screen matched for light emission - good film/screen contact to avoid artifacts - x-rays interact w/ entrance surface of screen - resolution > 11 lp/mm |
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Digital Mammo
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- can manipulate contrast & density
- transmit images anywhere for reading - better for women w/ dense breasts |
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Charge-Coupled Devices (CCD)
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- amorphous silicon-CsI (cesium iodide) & amorphous selenium
- x-ray interacts w/ screen & produces light, captured by fiber-optic bundle or lens system, directed to CCD, electron signal is read in pixels to form image |
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Direct Digital Mammo Equipment
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- converts image to electric signal w/o CCD
- selenium flat panal (most common) or phosphor flat panel display - x-rays absorbed & converted into an electrical charge by system of electrode pads - doesn't use AEC - 8-10 lp/mm average |
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Daily Quality-Control Measures
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- clean darkroom
- base plus fog density has to be within +0.03 of established operating level - mid-density has to be within +/- 0.15 of established operating level |
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Weekly Quality-Control Measures
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- optical density @ center of phantom image must be at least 1.20
- density difference btw. background & added test subject can only vary by +/- 0.05 from established operating level |
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Quarterly Quality-Control Measures
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- residual fixer no more than 5 mg/cm^2
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Semi-Annual Quality-Control Measures
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OD from darkroom fog can't exceed 0.05
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Annual Quality-Control Measures
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- compression device performance (force of at least 111 N [25 lbs])
- screen-film contact (use 40 mesh copper screen) |
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Signal Noise Ratio
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- image has electronic "noise"
- looks like quantum mottle but is more like base plus fog on radiograph - increase noise, decrease contrast - doesn't affect density - high ratio is best |
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Sensitometry
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- measurement of characteristic responses of film to exposure & processing
- usually performed @ beginning of morning shift - performed by same person, record the info |
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Penetrometer (step wedge)
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- aluminum composition
- good method for monitoring x-ray equipment & correct film/intensifying screen combos - uniform graduations |
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Sensitometer
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- electronic device designed to expose film to create a reproducible, uniform, optical step-wedge image onto film
- contains controlled intensity light source - circuits supply an exact quantity of power to the capacitor to control voltage fluctuations |
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11 step version increases density by ________ every step
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100% (a factor of 2)
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21 step version increases density by _______ every step
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41% (factor of 1.41)
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What can be detected by sensitometric equipment?
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Very slight density differences
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Densitometer
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- reads the "light transmission" through processed film
- provides readout of amount of density on film - "zero" out the densitometer, place exposed & processed sensitometry film onto stage, place sensor arm against film, press button to measure |
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Proper step on film is determined by the step reading closest of an OD of ______
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1.0
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Optical Density Numbers
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- numeric value produced is a result of the amount of light transmitted through the density of the film
OD = log(sub)10 (Io/I1) |
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Radiographic film has a density range of ______________.
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0.0 to 4.0
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What does 1.0 OD mean?
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10% (1/10th) of incident light is transmitted through radiograph
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Increments of 0.3 change in OD represents..........
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A doubling or halving opacity
1.3 OD = opacity doubled, % of light transmitted is halved 0.7 OD = opacity halved, % of light transmitted is doubled |
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Clear areas of the film will be represented by ___________ numbers, while dark areas of the film are represented by __________ numbers.
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Smaller; Larger
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Sensitometric Curves (D log E, H&D Curve)
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- graphic relationship between the amount of exposure & the resultant
- horizontal axis = logarithmic scale - vertical axis = a linear scale demonstrating OD Look at Table 21-1 |
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Components of the Curve
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Base plus fog, toe, straight line portion, shoulder, & Dmax
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Base plus fog (b+f)
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- inherent amount of density present in the film w/o exposure (max amount of light transmission)
- OD of base is 0.05-0.10; should never exceed 0.22 OD - base density is caused by blue tinting - fog caused by heat, chemical fumes, light, & radiation |
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Toe
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- phenidone is responsible
- controls subtle gray tones during processing - first thing to cause a change in density on film |
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Straight Line Portion
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- film is reacting in linear fashion
- low end is between 0.25-0.50; high end is between 2.0-3.0 - majority of diagnostic quality info will measure between 0.5-1.25 OD |
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Shoulder
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Hydroquinone controls this
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Maximum Density (Dmax)
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- represents point where all the sensitivity specks have a full complement of silver atoms & cannot accept more
- maximum density the film is able to record |
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Solarization
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Exposure beyond Dmax will result in less density b/c silver atoms attached to sensitivity specks will be ionized again, reversing their charge & causing them to be repelled from speck
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Film Characteristics
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Resolution, speed, contrast, latitude
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Resolution
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- detail, sharpness, definition
- measured by ability to see pairs of lines - unit = line-pairs/mm - diagnositc radiology has resoltuion of 1 lp/mm |
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Film resolution is determined by _________ of silver halide crystals
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Size
Inverse relationship between crystal size & resolution |
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Speed
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- determined by phenidone
- at the beginning location of toe (farther to the left that curve starts, faster the speed) - Directly Related --> film speed & crystal size, film speed & thickness of emulsion, film speed & number of sensitivity specks |
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Speed Point
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- point on D log E curve where a density of OD 1.0 + b + f is achieved
- Y axis of graph |
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Speed Exposure Points
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- log exposure that will produce the speed point for a given film
- X axis of graph |
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Speed is affected by:
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Immersion time (longer immersed, darker the film), Solution Temp (0.5 degree change in temp will have visible effect on density), & Chemical Activity
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Contrast
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- difference between adjacent densities
- determined by shape of H&D curve - defined by slope of straight line portion of curve - steep slope = high contrast, gradual slope = low contrast - controlled by hydroquinone |
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Latitude
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Latitude = Eh - E1 Eh = OD 2.5 exposure point, E1 = OD 0.25 exposure point
LATITUDE & CONTRAST ARE INVERSELY RELATED |
