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film and processing

chapter 9

QuestionAnswer
types of film screen film and direct exposure film
parts of film super coat=outer most laye emulsion=gelatin adhesive layer=bonds emulsion base base layer=inner most layer
base layer polyester/plastic=gives stability blue dye= to decrease eye strain substance to prevent crossover
crossover effect unique to double emulsion film used with intensifying screens. occurs when light exposes the first emulsion then crosses over the base to expose the other emulsion. reduces RD
emulsion layer -Radiation/light sensitive -very fragile and must have plastic base for stability -consists of silver halide crystals (silver bromide and silver iodine in gelatin) -silver halide: the material that is sensitive to light
silver halide crystals -made of mostly of silver bromide and a small amount of silver iodine. -silver is a positive ion -bromide and iodine are negative ions
supercoat layer (outer most layer) durable,protective outside layer intended to prevent damage to sensitive emulsion underneath.
film characteristics 1.film speed 2.film contrast 3.exposure latitude 4.spectral sensitivity
film speed increase speed=increase sensitivity to light= decrease exposure to produce density.
film contrast ability of film to provide levels of contrast (differences in two adjacent densities shade of gray) -levels of contrast mostly depend on manufacture -high contrast film=more black & white -low contrast film=more gray
exposure latitude range of exposure that can be used with a film to produce diagnostic densities -wide latitude -narrow latitude
wide latitude decrease contrast=adequate exposure of film with wide range of mAs values=more gray=low contrast
narrow latitude increase contrast=differentiate more strikingly with densities because of high contrast= black &white
spectral sensitivity the color of light to which a particular film is most sensitive
wave length that panchromatic is sensitive to blue sensitive
wave length that orthochromatic is sensitive to green sensitive
storing of unexposed film -store in original packaging for info (light sensitivity ,exp date,speed,size etc.) -store vertically -store away from heat and radiation(cause fog) -use First In First Out system (FIFO)
storage temp for unexposed film 50*-70*F above 75*F increases fog
storage humidity for unexposed film 40-60% humidity less than 40% humidity increases likelihood of static discharge
what is a latent image image on the film after exposure to x-ray but before processing -invisible
what is a manifest image image on film after processing -visible
processing converting latent image into the manifest image
automatic processor a device that encompasses chemical tanks,roller transport system and a dryer system for processing film
processing cycle the amount of time needed to process 1 film (45 sec-3-5 minutes)
processor capacity -number of films processed per hour.based on sizes of films processed -capacity is expressed in number of various sizes of film processed in 1 hour or number of various sizes of film processed in 1 hour
4 stages of processing in order 1.developing 2.fixer 3.washer 4.dryer
3 tanks in processor developing- deepest and film spends the most in it fixing-next deepest and film spends less time in the fixer then the developer washing-least deep and film spend the least amount of time here
developing primary function to create a latent image to manifest image
developing secondary function -increase amount for metallic silver on film by increasing the number of silver atoms in each latent image center -reduce amount of silver halide crystals into metallic silver
process of developing solution causes the emulsion to swell in order to allow interaction between chemicals and silver halide. solution donates an e- to sensitivity speck and therefor attracts more silver to the area of the sensitivity speck
what is the effect of time and temperature of developer? increase time and temp.=increased density=increased fog decrease time and temp=decreased density=film underdeveloped
6.agents in the developer 1.developer/reducer 2.accelerator/activator 3.restrainer 4.preservative 5.hardener 6.solvent
developer tank: developing/reducing agent -reduces exposed silver halide to metallic silver and add e- to exposed silver halide. -swells emulsion to allow for interaction between silver halide of film and chemicals in solution
developer tank:accelerator/activator (buffering agent) purpose: to elevate and maintain PH of solution (decreased ph=decreased activity) developer is a alkaline/basic solution
developer tank: restrainer purpose: it is used to decrease the amount of reduction of unexposed silver halide. -controls chemical fog that can be caused by too much reduction/development
developer tank:preservative purpose:to decrease oxidation and prolong life of developer solution
developer tank:hardener purpose:hardens emulsion after swelling due to reducing agents. protects the image from being damaged by roller system while moving into fixer tank.
developer tank:solvent purpose:to dilute chemicals so that they aren't too potent -water
oxidation decreased chemical activity. 2 types: aerial oxidation and use oxidation
aerial oxidation decreased chemical strength due to exposure to air -affects developer because of air from feed tray
use oxidation decreased chemical strength due to increased temperature over extended period of time affects developer and fixer
primary purpose of the fixer -to remove all undeveloped/unexposed silver halide (without affecting the metallic silver image) -make the manifest image permanent
secondary function of the fixer -stops development process -farther hardens emulsion and make image permanent
5 agents of fixing solution 1.fixing agent 2.acidifier 3.preservative 4.hardener 5.solvent
fixer tank: fixing agent purpose:to clear undeveloped silver halide from the film
fixer tank: acidifier purpose: to stop development process and create acidic ph for fixing agent
fixer tank: preservative purpose: to protect fixing agent from oxidation and maintain activity level
fixer tank:hardener to harden emulsion and create the permanent manifest image
fixer tank:solvent purpose: to dilute chemicals -water
cross contamination fixer crossing over into the developer can disrupt the effectiveness of th developer solution.
washing purpose:to remove fixer from film
drying purpose:to remove 85-90% moister from film radiographs must retain 10-15% moister too little will cause cracking
10 components of the vertical transport system 1.feed tray 2.entrance rollers 3.transport rollers 4.turnaround rollers crossover rollers 5.crossover rollers 6.guide plates (shoes) 7.motor drive 8.replenishment system 9.recirculation system 10. temperature control
feed tray flat metal surface with edges on either side that permits the film to enter easily and correctly aligned.
entrance rollers corrugated rollers that accepts film and orients it correctly for travel
transport rollers move film through the tanks and dryer system,found on either side of the roller assembly,rollers are usually staggered of set
turnaround/master rollers aka deep rollers found at the bottom of the roller assembly in each tank that turns the film from a downward to an upward direction
crossover roller found between tanks. transports film from one tank to another. the rollers are very tight to act as a squeege to decrease the amount of transfer fluid
guide shoes/plates slightly curved metal plates that guide the film between the rollers
what happens when guide shoes are in misalignment? cause emulsion to get picked off at the corners or edges
drive system electric motor that provides power to the roller transport system
drive system:stand by control electric circuit that shuts off the power to the assembly and washer system when the processor is not in use. saves on wear and tear of processor
replenishment system replacement of fresh chemicals after loss of chemicals during processing. fixer & developer can become exhausted and decrease function
replenishment system based on size replenishment system of developer and fixer is activated and pumps fresh chemicals for as long as the piece of film is in the entrance roller.film must be place crosswise to avoid over replenishment.
flood replenishment system replenishment of solution at timed intervals during standby regardless of size or number of films processed.
what happens when chemicals are over replenished? too many new chemicals. developer=increased density/decreased contrast fixer=overall wasting of solution
what happens when chemicals are under replenished? too many old chemicals! developer=films jam because of lack of hardener fixer=films jam because of lack of hardener and leads to poor archival quality
recirculation keeps chemicals mixed=maintains solution activity=agitation of chemicals=fast processing
developer temperature 93*-98* depending on speed of processor
3 types of temperature controls 1.water jackets 2.immersive heater 3.in-line heat exchanger
temperature control:water jackets located around the developer tank and uses hot and cold water to increase/decrease temp appropriately
temperature control:immersive heater heating coil immersed in tank and controlled by thermostat -cold water tank only needs cold water supply
temperature control: in line heat exchanger located in recirculation system of developer that heats water to proper temp before recirculation back into tank
drying system -squeegee rollers from washer to dryer -90 sec. processor: hot air blown onto both sides of film -slower processors: infrared lamps
safelight wattage range 7.5-15W
silver recovery purpose:removal of silver from fixer solution -use fixer has high amounts of silver -silver is a heavy metal and must be disposed of according to government regulations
temperature storage of exposed film 60*-80*F
humidity temperature storage of exposed film 30-50%
Created by: lchadderton