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Image Production
Film Construction
| Question | Answer |
|---|---|
| Who discovered photographic film? | william talbot in 1840 |
| What are the two components of film construction? | base & emulsion |
| Modern film has a base of what thickness? | 0.2 mm |
| Why is the base tinted blue? | to make it easier on the yes when viewing radiograph |
| WHat is the purpose of the base? | to provide support for the film emulsion |
| What makes up the emulsion? | silver bromide suspended in gelatin |
| What type of emulsion is used in x-ray film? | silver halide and gelatin |
| What molecules in the emulsion are most sensitive to visible light? | silver bromide (AgBr) |
| Concerning emulsion, what is the name of the process of heating the mixture? | digestion |
| Why is gelatin used in emulsion? | bc chemically it is a colloid |
| WHat does colloid mean? | allows things to distribute evenly |
| Where does gelatin come from? | calves skin and bones |
| What is an inherent problem with double sided coating emulsion? | parallax motion-a slight distortion of the image |
| The speed of the film is increased by doing what to the size of the crystals or thickness of the emulsion? | increasing |
| By increaseing the speed with crystal size or thickness of emulstion, what effect does this have on image detail? | impairs |
| Which grain emulsions are the fastest? | large |
| What types of crystals are flat with the flat side facing the x-ray tube? | t-grain |
| 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 |
| What charge do bromide ions ( Br-) have and why? | Negative, bc they have an extra electron |
| WHat charge do silver ions(Ag+) have and why? | positive bc they have a one-electron deficit |
| -invisible image in the film emulstion that is made visible upon development | latent image |
| Where does the formation of the latent image occur? | at the sensitivity speck located in the emulsion |
| At crystal level, what is the latent image? | a collection of silver atoms |
| The conversion of metallic silver to black metallic silver occurs when? | the film is immersed in developer chemicals of the processor |
| The ____ image which appears after development is called the _____ image. | visible manifest |
| The majority of processed radiographs in diagnostic radiography are considered to be what kind of images? | negative |
| In a radiographic image, the "shadows" are which part? | white regions, where the x-rays were blocked by the object) |
| In the radiographic image, the black region is which part? | where the x-rays were not stopped and passed through to expose the film |
| What is the most common type of film? Why? | screen film Designed to have the max sensitivity to the light emitted by the screen |
| Blue sensitive film responds to what kind of light? | blue and violet from calcium tungstate screens |
| Green sensitive/orthochromatic film responds to what kind of light? | blue and green light from rare earth screens |
| Where does radiography begin and end? | in the darkroom |
| An exposure as low as ____ mR can caused detectable film fog. | 5 |
| -a hallway that consists of several turns before entering the actual darkroom | maze or labyrinth |
| What is the most popular type of door used for darkroom entrances? | revolving door |
| What is the working distance from the safelight? | no less than 1 meter (3 ft) |
| What is the blub wattage that should be used for a safe light? | 15 watts |
| 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 |
| 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 |
| -marks or surious images that sometimes appear on the processed radiograph | artifacts |
| White crescent marks are put on the film before or after exposure? | before |
| Black crescent marks are put on the film before or after exposure? | after |
| What reduces contrast and increases the fog of a radiograph? | heat |
| Radiographic film should not be stored at temperatures in excess of? | 20 deg C ( 68 deg F) |
| Film storage for a yr or longer is acceptable if the film is maintained at what temp? | 10 deg C ( 50deg F) |
| What humidity level should film be stored at ? | btwn 40-60% |
| Above ____% humidity and contrast will be reduced and fog increased | 60 |
| Below __% humidity and there is an increase in static artifacts | 40 |
| What are 3 types of static? | tree/branch crown smudge |
| Most hospitals receive film on what basis? | monthly |
| What is the reasonable max storage time for radiographic film? | 45 days |
| -the study of the response of an image receptor to x-rays | sensitrometry |
| THe fog level of unprocessed film is approx ___ mR | 0.2 |
| What is another name for the h & D curve and LogE chart? | Characteristic curve |
| What is the range that radiographic film is sensitive to? | 5 - 1000 mR |
| What are the two factors that affect a characteristic curve ? | exposure and processing |
| -shows the lightest portion of the film | toe |
| -shows the darkest portion of the film | shoulder |
| -area of avg radiographic density; the diagnostic range | straight line portion |
| What is past the shoulder of the curve? | solarization point |
| What is the Dmax | the darkest area on the curve |
| What is the point just above the Dmax where additional exposure will begin to cause a decrease in radiographic density? | Solarization point |
| -an aluminum step-wedge | pentrometer |
| -device that measures optical density | densitometer |
| -when electromagnetic energy interacts with radiographic film, a density is produced within the emulsion | latent image formation |
| -a light exposure device which automatically adjust for changes in electrical current to ensure that each exposure made is uniform | sensitometer |
| 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) |
| Base density usually has a value of what? | 0.05 |
| Fog density on a radiograph should not exceed what? | 0.05 |
| Base plus fox should never exceed what? | 0.2 |
| What is the useful range of optical density? | 0.25 - 2.5 |
| What range do most radiographs show image patterns? | 0.5 - 1.25 |
| At what point is the optical density too dark to see anything? | over 2.5 |
| Mathematically, film contrast is equal which portion of the characteristic curve? | straight line portion |
| The ____ the straight line portion of the curve, the higher the contrast. | steeper |
| -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 |
| Speed = ? | 1 divided by roentgens needed to produce an optical density of 1 |
| The closer the curve is to the ___ the faster (higher) the film speed. | left |
| -the range of acceptable error | latitude |
| contrast and latitude are _____ proportional. | inversely |
| The ____ the straight line portion of the curve, the less the latitude. | steeper |
| The ____ the straight line portion, the higher the contrast. | steeper |
| What 4 things does the characteristic curve show? | base plus fog film speed film contrast film latitude |
| Where does the greatest amt of variation occur? | processor |
| Processing control charts monitors what 3 factors? | speed, contrast, base-plus-fog |
| Processing control charts when used correctly and faithfully, can reduce repeat rates by as much as? | 35% |
| What 2 things do processing control charts reduce? | pt exposure and operating costs |
Created by:
erikasmith28
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