image receptors 1 Flashcards
what are the two ways to capture x rays?
film and digital
what are the two forms of film known as?
direct action
indirect action
what are the two forms of digital known as?
solid state sensor
photostimuable phosphur
what is the scanner called that is used for PSP?
vista scan tower
what are the advantages of using PSP?
-tolerated by most patients
-can be used with holders
what are the disadvantages of using PSP?
-can be easily damaged
-expensive
-sensitive to background radiation (daylight)- must be cleared every 24hrs if unused
how does PSP work?
-psp placed in mouth
-phosphur coated side exposed to X-rays (stable excited state)
-plate dropped into vista scan tower and scanned by red laser (unstable excited state)
-blue light is emitted and converted into image
when is the latent image produced?
when x ray energy is stored in electrons of phosphur crystals
this is later emitted as blue light
what converts blue light to image?
ADC
how does ADC convert blue light to digital signal?
each pixel is given numerical value depending on intensity of light detected
-each numerical value represents shade of grey
-this forms image
how is residual energy in phosphor electrons erased?
by bright light
what are the two forms of solid state sensors?
CCD and CMOS
what are the four layers of sensors?
front layer
scintillator layer
silicone water layer
back layer
what happens at the scintillator later?
x ray is converted to light
what happens at the silicone water late?
light is converted to electrical signal after it hits photosensitive cells
what happens at back cover layer?
it is connected to pc and carries signal to computer
in CCD, how are pixels connected and how are the formed?
pixels are connected to neighbours and signals are formed in lines
what is the difference between CCD and CMOS?
it is the same process but in CMOS photosensitive cells are isolated and each released a signal instead of in lines
what are the advantages of Digital over film?
-no chemicals
-less storage
-no ventilation needed for hazardous chemicals
-image processed faster
-can edit image
-archive image
-easily transferable
-dose reduction as less repeats
what are the disadvantages of using digital over film?
-easily damaged
-image not as detailed
-stored on software- power cut-cyber attack?
-security- may be transferred to wrong place
-hackers
-may over edit image- affects diagnosis
how are images stored?
locally and backed up nationally
what is the storage system called in DDH?
PACS
where are images stored and backed up?
NHS tayside and national archive
what size of film is always used for solid state sensor?
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