Film Construction
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| Who discovered photographic film? | william talbot in 1840
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| What are the two components of film construction? | base & emulsion
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| Modern film has a base of what thickness? | 0.2 mm
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| Why is the base tinted blue? | to make it easier on the yes when viewing radiograph
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| WHat is the purpose of the base? | to provide support for the film emulsion
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| What makes up the emulsion? | silver bromide suspended in gelatin
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| What type of emulsion is used in x-ray film? | silver halide and gelatin
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| What molecules in the emulsion are most sensitive to visible light? | silver bromide (AgBr)
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| Concerning emulsion, what is the name of the process of heating the mixture? | digestion
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| Why is gelatin used in emulsion? | bc chemically it is a colloid
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| WHat does colloid mean? | allows things to distribute evenly
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| Where does gelatin come from? | calves skin and bones
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| What is an inherent problem with double sided coating emulsion? | parallax motion-a slight distortion of the image
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| The speed of the film is increased by doing what to the size of the crystals or thickness of the emulsion? | increasing
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| By increaseing the speed with crystal size or thickness of emulstion, what effect does this have on image detail? | impairs
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| Which grain emulsions are the fastest? | large
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| What types of crystals are flat with the flat side facing the x-ray tube? | t-grain
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| WHat allows the film speed to be faster without loosing detail? | the flatness of the t-grain allows the crystals to capture more light with out the need of thickening the emulsion
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| What charge do bromide ions ( Br-) have and why? | Negative, bc they have an extra electron
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| WHat charge do silver ions(Ag+) have and why? | positive bc they have a one-electron deficit
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| -invisible image in the film emulstion that is made visible upon development | latent image
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| Where does the formation of the latent image occur? | at the sensitivity speck located in the emulsion
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| At crystal level, what is the latent image? | a collection of silver atoms
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| The conversion of metallic silver to black metallic silver occurs when? | the film is immersed in developer chemicals of the processor
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| The ____ image which appears after development is called the _____ image. | visible
manifest
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| The majority of processed radiographs in diagnostic radiography are considered to be what kind of images? | negative
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| In a radiographic image, the "shadows" are which part? | white regions, where the x-rays were blocked by the object)
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| In the radiographic image, the black region is which part? | where the x-rays were not stopped and passed through to expose the film
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| What is the most common type of film? Why? | screen film
Designed to have the max sensitivity to the light emitted by the screen
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| Blue sensitive film responds to what kind of light? | blue and violet from calcium tungstate screens
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| Green sensitive/orthochromatic film responds to what kind of light? | blue and green light from rare earth screens
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| Where does radiography begin and end? | in the darkroom
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| An exposure as low as ____ mR can caused detectable film fog. | 5
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| -a hallway that consists of several turns before entering the actual darkroom | maze or labyrinth
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| What is the most popular type of door used for darkroom entrances? | revolving door
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| What is the working distance from the safelight? | no less than 1 meter (3 ft)
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| What is the blub wattage that should be used for a safe light? | 15 watts
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| How is a safelight test preformed? | subject film to small amt x-ray exposure; remove film in darkroom; cover one half of film with black paper and leave it exposed; process the film normally
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| How do you read the results of a safelight test? | If the uncovered portion of the film is darker than the covered area, you may conclude that the darkroom lighting is unsafe
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| -marks or surious images that sometimes appear on the processed radiograph | artifacts
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| White crescent marks are put on the film before or after exposure? | before
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| Black crescent marks are put on the film before or after exposure? | after
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| What reduces contrast and increases the fog of a radiograph? | heat
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| Radiographic film should not be stored at temperatures in excess of? | 20 deg C ( 68 deg F)
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| Film storage for a yr or longer is acceptable if the film is maintained at what temp? | 10 deg C ( 50deg F)
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| What humidity level should film be stored at ? | btwn 40-60%
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| Above ____% humidity and contrast will be reduced and fog increased | 60
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| Below __% humidity and there is an increase in static artifacts | 40
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| What are 3 types of static? | tree/branch
crown
smudge
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| Most hospitals receive film on what basis? | monthly
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| What is the reasonable max storage time for radiographic film? | 45 days
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| -the study of the response of an image receptor to x-rays | sensitrometry
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| THe fog level of unprocessed film is approx ___ mR | 0.2
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| What is another name for the h & D curve and LogE chart? | Characteristic curve
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| What is the range that radiographic film is sensitive to? | 5 - 1000 mR
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| What are the two factors that affect a characteristic curve ? | exposure and processing
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| -shows the lightest portion of the film | toe
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| -shows the darkest portion of the film | shoulder
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| -area of avg radiographic density; the diagnostic range | straight line portion
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| What is past the shoulder of the curve? | solarization point
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| What is the Dmax | the darkest area on the curve
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| What is the point just above the Dmax where additional exposure will begin to cause a decrease in radiographic density? | Solarization point
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| -an aluminum step-wedge | pentrometer
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| -device that measures optical density | densitometer
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| -when electromagnetic energy interacts with radiographic film, a density is produced within the emulsion | latent image formation
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| -a light exposure device which automatically adjust for changes in electrical current to ensure that each exposure made is uniform | sensitometer
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| Unexposed radiographic film has an optical density in the range of what? | 0.1 to 0.15 ( 80% of the light is allowed to be transmitted)
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| Base density usually has a value of what? | 0.05
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| Fog density on a radiograph should not exceed what? | 0.05
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| Base plus fox should never exceed what? | 0.2
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| What is the useful range of optical density? | 0.25 - 2.5
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| What range do most radiographs show image patterns? | 0.5 - 1.25
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| At what point is the optical density too dark to see anything? | over 2.5
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| Mathematically, film contrast is equal which portion of the characteristic curve? | straight line portion
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| The ____ the straight line portion of the curve, the higher the contrast. | steeper
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| -the ability of an x-ray film to respond to a min quantity of x-ray exposure is a measure of what? | its sensitivity or speed
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| Speed = ? | 1 divided by roentgens needed to produce an optical density of 1
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| The closer the curve is to the ___ the faster (higher) the film speed. | left
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| -the range of acceptable error | latitude
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| contrast and latitude are _____ proportional. | inversely
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| The ____ the straight line portion of the curve, the less the latitude. | steeper
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| The ____ the straight line portion, the higher the contrast. | steeper
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| What 4 things does the characteristic curve show? | base plus fog
film speed
film contrast
film latitude
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| Where does the greatest amt of variation occur? | processor
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| Processing control charts monitors what 3 factors? | speed, contrast, base-plus-fog
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| Processing control charts when used correctly and faithfully, can reduce repeat rates by as much as? | 35%
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| What 2 things do processing control charts reduce? | pt exposure and operating costs
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