Film Factors Flashcards
The study of the relationship between the intensity of exposure of the film and “the blackness after processing” is called
Sensitometry
Film Factors is consists of
Speed
Contrast
Density
Latitude
Processing temperature
Processing time
The “two principal measurements” involved in sensitometry are the___________and___________
-exposure to the film
-Percentage of light transmitted through the process film
Types of characteristics curve
H&D curve
Hurter and Driffield
It describe the relationship between OD and radiation exposure
Characteristic curve
-low radiation exposure level
Toe
-intermediate radiation exposure level
-the region in which properly exposed radiograph appears
Straight line portion
-high radiation exposure level
Shoulder
Apparatus that are needed to construct a characteristic curve
Optical step wedge/sensitometer
Densitometer - a device that measures OD
Steps involved in the construction of a characteristic curve
Exposure the film
Process the film
Analyze the film
Record and plot data
The degree of blackening on the radiograph
-has a precise numeric value
Optical Density
Attributable to the composition of the base and the tint added to the base to make the radiograph more pleasing to the eye.
-has a value of approximately 0.1
Base Density
Results from “inadvertent exposure of film during storage”, undersirable chemical contamination, improper processing, and a number of other influences
- on a processed radiograph should not exceed 0.1
Fog density
States that the “OD on a radiograph is proportional only to the total energy imparted to the radiographic film” and independent of the time of exposure
Reciprocity Law
Is inherent in the screen-film combination and is “influenced somewhat by processing of the film”.
Image receptor contrast
Is “determined by the sized, shape, and x-ray attenuating characteristics of the anatomy” that is being examined and the energy (kVp) of the x-ray beam
Subject Contrast
Is probably “more important than average gradient for general radiography” because many clinical ODs appear in the toe region of the characteristic curve
Toe gradient
Is more important for mammography
Midgradient or shouldrr gradient
Refers to the “range of exposures” over which the image receptor responds with ODs in the diagnostically useful range.
Latitude
Latitude and contrast are
Inversely proportional
Development time is______ and the IR speed and Fog is_______, IR contrast is
High, high, low
Development Temp is ______, IR speed is________ and fog is __________
High, high, High
Is “related to the slope of the straight line portion” of the characteristic curve
Film contrast
Wide latitude have
Long gray scale
Low contrast
Narrow latitude have
Short gray scale
High contrast
Fast/high speed IR
More than 100
Par speed
100
