Image Receptors 1 Flashcards
types of film?
direct action film
indirect action film
types of digital film?
solid state sensor
PSP’s
what is direct film?
dental intra oral
xrays act directly on silver halide crystals on film emulsion
what is an indirect film?
extra oral
light from intensifying screens act on silver halide crystals in film emulsion
what is DR?
solid state CCD, CMOS sensor
what is CR-PSP?
latent image produced by interaction of xrays with phosphor layer of plate
scanned by laser to produce image
PSP action when in a patients mouth?
phosphor layer absorbs and stores xray energy in the electrons of the phosphor crystals
PSP action when taken to scanner?
plate inserted into scanner
plate scanned by red laser
light released
light detected by photomultiplier tube
how is an image produced from a PSP plate?
light = electrical signal
relayed to computer - digital image
residual energy trapped in electrons after scanning
image on plate erased by exposing PSP to bright light
plate ready to re use
what state is a psp plate in when acted on by an xray?
stable excited state
what happens to the stable excited state plate when acted on by red laser?
unsatble excited state
how is the unstable excited plate turned back to a normal imaging plate?
scanner collects blue light and converts to an image
layers of a CCD plate?
back cover + cable to PC
silicon wafer - light to electrical signal
scintillator layer - x ray energy to light
how is an image produced from a CCD plate?
x rays hit scintillator layer = light
light hits photosensitive cells in silicon layer = pixels of image
electrons released in each cell = charge that is converted to a voltage = electrical signal = image
what is the signal the computer receives made up of?
lines of pixels
each pixel connected to its neighbour
how does CMOS work?
similar except photocells are electrically isolated
charge to volatge signal is made up of each individual cell instead of lines
what gives the better quality image?
CCD
what is cheaper?
CMOS
what is more reliable?
CCD
what uses less power?
CMOS
advantages of digital images?
no chemicals easily archived easy image transfer image can be manipulated reduced pt dose
disadvantages of digital images?
expensive
reduction in resolution because of pixel size
archiving = problem because of back up
how are x rays stored at a dental practice?
local storage
PC
back up = CD, DVD, hardrive
where is PACS stationed?
locally - NHS Tayside
nationally - Livingstone
