Digital and Film Radiography Flashcards
what are the x-ray receptors used in digital radiography
phosphor plate
solid state sensor
what are the receptors used in film radiography
direct action film
indirect action film
what are the sizes of the phosphor plates
0,2,4
what is size 0 used for
anterior periapicals
what is size 2 used for
bitewings, posterior periapicals
what is size 4 used for
occlusal radiographs
what causes an x-ray shadow
the x-ray beam passes through an object and some of the x-ray photons are attenuated
what is an x-ray shadow
image held by x-ray photons after x-ray beam has passed through object
what is the interaction between the image receptor and the x-ray shadow
it detects the x-ray shadow and uses it to create an image
what does the receptor do
measures the x-ray intensity at defined areas
what is the digital image displayed as
grid of squares called pixels
what is the benefit of more pixels
better detail and higher resolution
what will increasing the resolution do
provide a more diagnostic image up to a limit
what is the issue with having more pixels
need more storage space so increased cost
how many bits are radiographs processed in
at least 8 bits
what do bits refer to
number of different shades of grey available
what does DICOM stand for
digital imaging and communications in medicine
what is DICOM
international standard format for handling digital medical images
what does DICOM allow for
imaging to work between different software, machines, manufacturers, hospitals, countries without compatibility issues
what does PACS stand for
picture archiving and communication system
what is PACS
medical imaging technology which provides storage and access to images
what are the main components of PACS
input by imaging modalities
secure network for the transmission of patient information
workstations for interpreting and reviewing images
archives for the storage and retrieval of images and reports
what kind of environment is needed to view digital radiographs
subdued lighting and avoiding glare
what should the monitor be like when viewing radiographs
clean, adequate display resolution, high enough brightness level, suitable contrast level
after taking an x-ray how do you process it with a phosphor plate
put it in a scanner
how are images created using phosphor plates
phosphor crystals in receptor excited by the x-ray energy, resulting in the creation of a latent image
what happens to the phosphor plate inside the scanner
laser energy causes excited phosphor crystals to emit visible light which is detected and creates a digital image
what are the 2 types of solid state sensor
CCD (charge coupled device)
CMOS (complimentary metal oxide semiconductor)
how are images created with a solid state sensor
latent image created and immediately read within the sensor itself
what is the purpose of the identification dot
aid orientation of image
what is used for cross infection with intra oral receptors
purpose made covers to prevent saliva contamination - single use
what are the advantages of the phosphor plates
thinner, lighter, flexible
wireless and more stable
what are the disadvantages of phosphor plates
variable room light sensitivity so risk of impaired image
latent image needs to be processed in scanner separately
what are the disadvantages of solid state sensors
bulkier and rigid
wired
smaller active area
what are the advantages of solid state sensors
more durable
no issues with room light control
more expensive
what are the layers of the intra-oral film packet
radiographic film
protective black paper
lead foil
outer wrapper
what is the purpose of the protective paper
protects film form light exposure, damage by fingers and saliva
what is the purpose of the outer wrapper
prevents ingress of saliva
indicates which side of the packet is the front
what is the purpose of the lead foil
absorbs some excess x-ray photons
what is the purpose of the radiographic film
material in which the image is formed
what is the radiographic film sensitive to
x-ray photons and visible light photons
what is the photon reaction on radiographic film
photons interact with emulsion on film to produce latent image which only becomes visible after chemical processing
what is the structure of the radiographic film
transparent plastic base
adhesive
emulsion
protective coating of clear gelatin
what is the purpose of the transparent plastic base
supports emulsion
what is the purpose of the adhesive
attaches emulsion to plastic base
what is the purpose of the clear gelatin coating
shields the emulsion from mechanical damage
what crystals are embedded in the gelatin binder of a radiographic emulsion
silver halide crystals
what do crystals become
pixels of final image
what is film higher resolution than digital
due to the microscopic crystals
what happens to the silver halide crystals when in contact with x-rays
become sensitised
what happens to the silver halide crystals during processing
converted to particles of black metallic silver and non-sensitised crystals removed
what does the lead foil do
absorb some excess photons
what is film speed
amount of x-ray exposure required to produce an adequate image
what does increased film speed do
decrease radiation required to achieve an image
what is film speed affected by
number and size of silver halide crystals
what is the purpose of intensifying screens
reduce radiation dose but also reduce detail
what do intensifying screens do
release visible light upon exposure to x-rays which creates latent image on film
where must film processing be carried out
under controlled, standardised conditions to ensure consistent image quality
what are the different methods of film processing
manual, automated
self developing
what are the steps of film processing
developing
washing
fixing
washing
drying
what is the developing phase of film processing
converts sensitised crystals to black metallic silver particles
what is the first washing phase of film processing
removes residual developer solution
what is the fixing phase of the film processing
removes non-sensitised crystals
hardens emulsion
what is the second washing phase of film processing
removes residual fixer solution
what is the drying phase of film processing
removes water so that film is ready to be stored
what is involved in a manual cycle
person dips film into different tanks of chemicals at precise concentrations/temperatures for specific periods of time
where must manual processing be carried out
in a dark room with light tightness and adequate ventilation
what is involved in the automated processing cycle
steps carried out in a machine where film goes in one end and out the other
how do you open a film packet for automated processing
disinfect packet
hold packet under hood of processor unit
peel back flap of outer wrapper
fold back lead foil
pull back paper flap
hold film by edges
insert film into processor
what are the issues with developing
chemical reaction affected by time, temperature and concentration of solution
solution can oxidise in air and become less effective
what are the causes of pale images
exposure issue (radiation exposure factors too low)
developing issue - film removed from solution too early/solution too cold/solution too dilate/old
what are the issues with fixing
inadequate fixing means non-sensitised crystals left behind - can be greenish/milky and become brown
what is the issues with washing
developer and fixer solution will continue to act if not washed
what are the advantages of digital radiography
no need for chemical processing
easy storage and archiving
easy back up of images
images can be integrated into records
easy transfer/sharing of images
images can be manipulated
what are the disadvantages of digital radiography
worse resolution
requires diagnostic level computer monitors for optimal viewing
risk of data corruption/loss
hard copy print outs have less image quality
image enhancement can create misleading images
