Digital and Film and Radiography Flashcards
digital vs film receptors
times they can be used
digital - multi use
film - single use
Greyscale bit depth
number of different shades of grey available
radiographs usually 8 bits - 2^8 = 256 shades of grey
How are digital receptors arranged
arranged in a grid with the squares of grid known as pixels
more pixels = more accurate image (higher resolution) up to a point*
each pixel can only display one colour
pixels measure intensity of beam (number of photons) reaching it with different intensities corresponding to different shades of grey
what effect does increased pixels have on file size and therefore storage (digital radiography)
increased pixels = increased file size = increased storage space required
what does PACS stand for
picture archiving and communication system
what are the 2 types of digital inta oral receptors
phosphor plates
solid state sensors
phosphor plate receptors
used in digital intra oral radiography
they are not connected to anything and must be ran through a separate scanner to create an image
within the patients mouth a latent image is created on the receptor, within the scanner a laser is used to convert this to a digital image
solid state sensors
used in digital intra oral radiography
connected to the computer - usually via wire but can be wireless
latent image created on the receptor is immediately read and an image produced on the computer
solid state sensors vs phosphor plates
price
solid state are more expensive
solid state sensors vs phosphor plates
impact of light
phosphor plate receptors may be damaged by light
solid state sensors vs phosphor plates
patient comfort
phosphor plate receptors thinner, less bulky and less rigid
also wireless
what is contained within a radiographic film receptor packet
radiographic film - on which actual image is formed
lead foil , lies behind film , to absorb excess photons
what 2 types of photons are x ray film sensitive to
x ray photons
visible light photons
how is a latent image created on film radiography
film contains silver halide crystals which become sensitised upon interaction with x ray photons
must be chemically processed to become visible - sensitised crystals are converted to particles of black metallic silver
what is the impact on having large silver halide crystals on a film rather than small
larger crystals results in faster production and therefore decreased patient dose however the image is of poorer quality
what are the 5 stages of film developing
developing
washing
fixing
washing
drying
what is done during the developing stage of film developing
sensitised crystals are converted to black metallic silver particles
what is done during the washing stages of film developing
removes residual developer and fixer solution
what is done during the fixing stage of film developing
removes non sensitised crystals
what is done during the drying stage of film developing
removes water so film can be stored
digital vs film radiography
digital requires no chemical processing, has easier storage, images can easily be manipulated and added to digital patient records
however they are of poorer resolution and risk data corruption
on the whole digital are superior
what would happen to the x ray image if developer solution was old and out of date (film radiography)
less silver halide crystals would be converted so the image would be lighter
what would happen if the developer solution was too warm or too concentrated (film radiography)
more silver halide crystals would be converted so the image would be darker
what would happen if there was inadequate fixation of an image (film radiography)
decreased contrast of image as excess crystals not removed
what would happen if film was exposed to visible light before processing
darker image would be produced as more crystals sensitised as film sensitive to both x ray photons and visible light photons
