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QM Registry Ch.3
F/S IR, Darkrooms, and Viewing Conditions
Question | Answer |
---|---|
The ratio between the image contrast to the amount of image noise (both quantum mottle and/or electronic); can be used to describe image quality | contrast-to-noise ratio |
The ability of an imaging system to distinguish structures with similar transmission as separate entities | contrast resolution |
Area protected from white light where films are processed | darkroom |
Electronic device for measuring the optical density of a film | densitometer |
A graphic indication of image resolution | edge spread function |
The type of luminescence that is desired for use in intensifying screens because it occurs when certain crystals emit light within 10-8 seconds after being exposed to radiation | fluorescence |
Measurement of illuminance; lumens per square foot = foot-candles | foot-candle |
A measure of resolution equal to the width of an image of a line source at points where the intensity is reduced to half the maximum | full-width half maximum (FWHM) |
A measurement of the relative level of moisture in the air | humidity |
The brightness of light projected on a given surface, measured in lux or foot-candles | illuminance |
A measurement of intensifying screen speed | intensification factor |
The increase in sensitivity of a film after it has been exposed to light or ionizing radiation so that it can be as much as two to 8 times more sensitive to subsequent exposure as an unexposed film | latensification |
The amount of luminous intensity emitted by a source of light | luminance |
The emission of light resulting from x-rays exiting the patient, which energize the phosphor crystals. It can occur by one of two different processes, fluorescence or phosphorescence | luminescence |
A graphic or numeric indication of image resolution | modulation transfer function (MTF) |
A unit to measure luminance, equivalent to candela per square meter | nit |
The highest spatial frequency resolved by an imaging system, measured in lp/mm | Nyquist frequency |
A type of film that is sensitive mainly to light in the green portion of the visible light spectrum | orthochromatic |
A type of film that is sensitive to all wavelengths of the visible light spectrum | panchromatic |
Delayed emission of light--often called afterglow or lag--not desired for use in intensifying screens that occurs when certain crystals emit light sometime after 10-8 seconds after exposure to radiation | phosphorescence |
The study and measurement of light | photometry |
A graphic demonstration of image resolution | point spread function |
An instrument used to measure relative humidity | psychrometer |
Image noise caused by statistical fluctuations in the number of photons creating the image | quantum mottle |
A relative number indicating the speed of an intensifying screen imaging system | relative speed |
A light source that does not fog film | safelight |
The amount of light that is emitted from an intensifying screen for a given amount of x-ray exposure | screen speed |
An electrical device that exposes the film to a premeasured light source for quality control purposes | sensitometer |
Used to describe the relative contributions to a detected signal of the true signal and random superimposed signals or noise | signal-to-noise ratio |
A decrease in optical density with an increase in exposure. AKA image reversal | solarization |
The ability of an imaging process to distinguish small, adjacent, high-contrast structures in the object | spatial resolution |
The matching of film sensitivity with the color of light emitted by the intensifying screen | spectral matching |
Electrical charges created by friction, which can cause artifacts on unprocessed film | static electricity |
A measure of the average kinetic energy in atoms and molecules of matter | temperature |
A type of electromagnetic radiation in between visible light and x-rays | ultraviolet radiation |
The process by which air is changed into and out of a specific area | ventilation |
An electronic device for viewing transparency images such as radiographs | viewbox illuminator |