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Image Production

Film Construction

QuestionAnswer
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