lecture final Flashcards
(32 cards)
In a variable KVP technique chart, for every cm increase in part thickness, the kvp is changed by:
increasing 2kvp
The phosphor coated detector in the AEC system does what?
converts radiation to light
where is the detector located in the exit type AEC system?
underneath or behind cassette
what does the capacitor do in the AEC system?
stores the electrical current
the phtotomultiplier tube is a _______ tube and does what?
vacuum tube, produces the electrical current
what produces the ion (electrical current) in the ionization chamber AEC system?
exit/image forming radiation
what factors will affect image density produced by an AEC system?
CR improperly centered
pathology
incorrect bucky switch selected
what is the direct square law used for? (old mAs/new mAs)
adjust the mAs when the SID is altered to maintain density
Collimating down from a 14x17 to an 8x10 field size, how will your technical factors need to be adjusted?
mAs increased by 60%
OR
add 10 Kvp
collimating down from a 14x17 to a 10x12 field size, how will your technical factors need to be adjusted?
mAs increased by 40%
OR
add 5 Kvp
fast speed screens: Phosphor size and layer, recorded detail/spatial resolution, mottle, dose, amount of mAs required
- large crystals, thick layer
- less recorded detail/ spatial resolution
- more mottle and noise
- decreases patient dose
- 200 speed screen requires 50% less mAs than 100 speed screen
slow speed screens: Phosphor size and layer, recorded detail/spatial resolution, mottle, dose, amount of mAs required
- small crystals, thin layer
- more recorded detail/spatial resolution
- less mottle/noise
- increases patient dose
- 100 speed screen would require 100% more mAs than a 200 speed screen would
in screen/film emulsion, what is the sensitivity speck?
a defect or flaw in the crystalline structure of screen/films liver bromide crystal. Its also a trap where black metallic silver is formed as the latent image
in a CR imaging plate, phosphors are stimulated with what’?
xray photon energy and fluoresce
what is developer oxidation?
refers to the giving up of electrons by developer reducing agents to reduce the silver atoms to black metallic silver to create the visible image.
what does developer selectivity mean?
the developer only reduces the exposed silver bromide crystals and leaves the unexposed intact.
what does the transport system do?
provides mechanical movement of film thru the processor at a controlled rate
what does the circulation system do?
responsible for agitation of the chemistry and constant filtering of the developer
what does the fast acting reducing agent establish?
gray and white shades of the visible/manifest image
-component of developer
what does the slow acting reducing agent establish?
black tones of the visible manifest image
-component of developer
what do the reducing agents do?
reduces exposed silver bromide crystals to black metallic silver and changes the latent image into a visible manifest image
-component of developer
what does the activator do?
swells the films emulsion
-component of developer
what is the pre hardeners job?
shrinks and hardens the films emulsion, prevents films from getting stuck together
-component of developer
what does the retrainer/antifog agent do?
prevents the reduction of unexposed silver bromide crystals
-component of developer
