Computed Radiography Flashcards
the CR reader processes the ___ image captured by the detector
the CR reader processes the latent image captured by the detector
what is in CR detectors that stores the latent image
photostimulate phosphor (PSP)
what happens when the PSP is stimulated by laser light in the CR reader
the phosphor emits light by stimulated luminscence
what is the quantity of light produced proportional to?
the x-rays absorbed
what detects the emitted light?
the Photomultiplier tube (PM tube)
the emitted light is of a different wavelength to the stimulating laser light - True or False?
True
what is the PSP made of
Europium activated Barium fluorohalide compounds
what is the PSP sandwiched between
protective layer and base support
what is the DQE
the % of x-ray photons absorbed by the phosphor
what effect does thicker phosphors have on DQE
thicker phosphors increase DQE
What is the limitation with thicker phosphors?
light cannot escape if the phosphors are too thick and the light won’t reach the PM tube
describe the PSP function
x-ray photon absorbed, creates multiple electron hole pairs
electrons get trapped in the F band
some electron hole pairs reunite immediately an produce light - these are not detected
the remaining electron hole pairs form the latent image
what happens to the electron hole pairs that reunite immediately when an x-ray photon is absorbed
these account for about 50% of electron hole pairs created, these do not get detected
what happens to the latent image when stimulated by laser
electrons escape from their traps and combine with the holes to produce light
is the light produced after the laser scanning higher or lower frequency than the laser
the light produced is higher frequency than the laser
what does the trapped electron distribution depend on?
trapped electron distribution depends on the incident x-ray exposure
the digitised signal is ____ to produce a satisfactory image using ____ ____ and ____ reduction
the digitised signal is processed to produce a satisfactory image using edge enhancement and noise reduction
how to reset the PSP
expose to high intensity white light
what does the white light exposure do to the PSP
returns electrons to their resting state and remove ghost images
what is the spatial resolution of CR
3.5-5 lp/mm
how does CR contrast resolution compare to film screen?
CR contrast resolution is better than film screen
what is there a risk of in CR and why?
risk of dose creep due to wide latitude/dynamic range
