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Carlton & Adler Ch40

Carlton & Adler Ch40 Fluoro

QuestionAnswer
Credited with inventing fluoroscope Thomas Edison 1896
Invention of image intensification tubes 1948
Primary function of fluoroscope real time imaging to provide visualization of dynamic processes as they occur
Transparent protective outer covering of the eye cornea
Where light is focused onto the retina lens
Between the cornea and lens in the eye Iris
Controls the amount of light that is admitted to the eye Iris
Where the light is focused in the eye retina
Where cones and rods reside in eye retina
Area where the cones are concentrated in the center of the retina fovea centralis
Where are rods found in the retina around the periphery
Illumination is measured in what? lumen per square meter or lux
Sensitive to low levels of light, 2 lux rods
Less sensitive to light, 100 lux cones
Daylight vision photopic
Night vision scotopic
Minimum SOD in fixed fluoro equipment 15 inches
Fluoroscopic mA range .5 to 5.0mA
Diagnostic mA range 50 to 1200mA
Five major components in image intensifier input screen, photocathode, acceleration anode, electrostatic focusing lenses, output phosphors.
In contact with input phosphor to prevent divergence of light beam photocathode
Absorbs the light photons and emits electrons photocathode
Absorbs x-ray photons and emits light photons input phosphor
Electrons accelerated from cathode to anode output phosphor
Primary brightness gain occurs from what acceleration & focusing of the electrons
Absorbs electrons & emits light phosphors output screen
Entire image intensifier is housed where inside lead lined housing
Input phosphor has _____mm of sodium activated cesium .1 - .2mm
Range of input phosphor range of diameters 6-23”
Why is input phosphor concave to maintain same distance between each point on input screen & corresponding location on output screen
Photocathode is composed of what cesium & antimony
What attaches photocathode to input phosphor protective coating
Process of turning light photons into electrons photoemission
How many light photons does it take to cause emission of one electron thousands (many)
Stimulation is _____ not _____ light not heat
Focused and accelerated electrons through the vacuum to the output phosphor electrostatic focusing lenses
Electrostatic focusing lenses create what to intensify electron beam electric potential
Positively charged, draws electrons away from the photocathode at a tremendous velocity accelerating anode
Output screen is made of what? silver-activated zinc-cadmium
Electrons are converted into light photons where in the image intensifier? output screen
Photoelectrons that arrive at the output phosphor provide ____ times as many light photons than were created 50-75 times
How does image intensifier improve fluoroscopy increasing brightness
Minification gain x flux gain brightness gain
Ratio of the illumination intensity at the output phosphor to the radiation intensity of the input phosphor brightness gain
Ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor minification gain
Increase in brightness or intensity, not in the quality or number of photons minification gain
Ratio of the number of light photons at output phosphor to the number of x-rays at the input phosphor flux gain
Increase in the brightness as a result of acceleration of the electron flux gain
Measurement of conversion efficiency of output screen flux gain
Switches the mode from larger to smaller, increases voltage on electrostatic focusing lenses multifield image intensification
Causes the focal point to move further from the output phosphor multifield image intensification
Principle result of multifield image intensification reduce the field of view and thereby magnify the image
Magnification mode results better spatial resolution, better contrast resolution, higher patient dose
Maintains brightness of the image by automatically adjusting the exposure factors according to subject density and contrast automatic brightness control
When is primary beam changed when using automatic brightness control when current and intensity fall below established limits
Difference between plumbicon & vidicon tubes different target materials & plumbicon has faster response time
Heated filament that supplies a constant electron current by thermionic emission electron gun
Steer and accelerate the electrons to the anode electrostatic grids
Parts of the cathode in video camera tube electron gun & electrostatic grids
Parts of the anode in the video camera tube window, signal plate, target
Thin part of glass envelope in anode window
Made of metal or graphite in the anode signal plate
Photoconductive later of antimony trisulfide in anode target
Two methods of attaching the image intensifier to the camera tube fiber optics & optic lens device
Disadvantage of fiberoptics in production of video signal cannot accommodate auxillary imaging devices such as cine or spot cameras.
Allows for image to be seen on the TV monitor to be recorded at same time optical lens device or lens coupling
Used to transmit part of the beam to the tv camera and remainder to the film camera beam splitting mirror
Most important critical elements in optical chain in terms of alignment camera lenses
Types of viewing systems video, cine, spot film, video camera tubes
recording device with higher patient dose cassette loaded spot film
records only one frame at a time photospot camera
can be viewed as movie or stop action film cine film
benefit of cine film increased resolution
drawback of cine film increased patient dose
how does cine film record? on video - VHS
SSD for portables 12"
SSD for stationary units 15"
requirements for lead apron must be worn by all persons present, at least .25mm of Pb/eq
lead gloves used lead content .25mm Pb/eq
primary source of exposure in fluoroscopy patient
radiographer's responsibility in fluoroscopy inform others in room to wear lead apron, do not initiate fluoro until all persons have complied
in fluoro, switching from 9" to 6" FOV results in ___ in the resolution and ___ in patient entrance exposure increases, increases
image intensifier improved fluoroscopy by increasing image brightness
what is the purpose of fluoroscopy to view dynamic anatomy
what comes last in the image intensifier? zinc cadmium sulfide screen
what conversion occurs in the image at the input phosphor of the image intensifier tube? x-rays are converted into visible light
raster when it is scanning active tracer
raster when it is moving back to the next starting point inactive tracer
what comes last in the image intensifier zinc cadmium sulfide screen
visual acuity in the eye is greatest at the __ where the __ are concentrated fovea centralis, cones
image intensifier improved fluoroscopy by increasing image___ brightness
in fluoro, switching from 9" to 6" FOV results in __ in resolution and __ in pt entrance exposure increase, increase
x-rays that exit the patient and enter the image intensifier first interact with the input phosphor
what conversion occurs in the image at the input phosphor in the image intensifier tube x-rays converted to visible light
how is magnification gain calculated input screen diameter / diameter of input screen used during magnification
measurement of the increase in image intensity achieved by an image intensification tube total brightness gain
input screen diameter squared / output screen diameter squared minification gain
output phosphor intensity is measured in what? candelas
major cause of size distortion in fluoro OID
vignetting or pincushion distorting distortion of edges of fluoro image because of concave input screen
where is contrast improved and distortion minimized? the center of the fluoro image
Created by: jen.studer