Digital & Film Radiography Flashcards
How do digital and film forms of radiography differ
they differ in how the x-ray beam is dealt with after it has interacted with the patient
What are the type of digital receptors
phosphor plate
solid sensor
both multiple use
What are the types of film receptors
direct action
indirect action
both single use
What aerate different measurements for the receptor size for phosphor plates
size 0 - anterior periapicals
size 2 - bitewings; posterior periapical
size 4 - occlusal radiographs
What is an x ray shadow
it is a pattern of attenuation that you see if you pass the x ray beam through an object
How does the x ray shadow get turned into an x ray density
the receptor measures the x-ray intensity at defined areas that are arranged in a grid
each area is given a value relating to x ray intensity
each value corresponds to a different shade of grey
What are the values relating to x ray intensity
range from 0-255
255 means that very few x ray photons are reaching the area
0 = black 255 = white
How is the digital image displayed
as a grid of squares called pixels
each pixel can only display one color at a time
more pixels you have the more accurate the image
What is the benefit of more pixels
better detail and a higher resolution
increasing the resolution will provide a more diagnostic image up to a limit
What is the issue if there’s too many pixels
digital image will require more storage space resulting in increased costs
Why are digital receptors limited in how small they can make the pixels
due to manufacturing challenges
How are radiographs typically processed in regards to greyscale bit depth
the radiographs are typically processed in at least 8 bits which refers to the different number of shades of grey available
you do 2^8 giving 256 meaning 256 shades of grey
How can a digital image be modified
contrast/widowing
negative
emboss
magnify
What is the format for digital images
DICOM - digital imaging & communications in Medicine
international standard format for handing digital medical images used to transmit, store, retrieve, print, process and display images
What are the benefits of DICOM
allows imaging to work between diff software, machines, manufacturers, hospitals and countries without compatibility issues
also stores other important data alongside the image
What is PACS
picture archiving and communication system
a medical imaging technology which provides storage and access to images (typically in healthcare organization)
What are the main components of PACS
input by imaging modalities e.g plain radiography, CT, MRI, US
secure network for transmission of px info
workstations for interpreting and reviewing images
archives fo rate storage and retrieval of images and reports
What environment should digital radiographs be viewed
subdued lighting
avoid glare
How should the monitor be prepared for viewing digital radiographs
should be
clean
adequate display resolution
high enough brightness level
suitable contrast level
What is the SMPTE test pattern
society of motion, picture and television engineers
available online
can be used to assess the resolution, contrast and brightness of your monitor/monitors
Describe phosphor plates
not connected to computer
after the receptor is exposed to X-rays it must be put in scanners and read to create the final image
Describe image creation using phosphor plates within the patients mouth
the receptor is exposed to the x ray beam
the phosphor crystals in the receptor are excited by the x ray energy resulting in the creation of a latent image
Describe image creation using phosphor plates within the scanner
receptor scanned by a laser
the laser energy causes the excited phosphor crystals to emit visible light
this light is detected and creates the digital image
What are the types of solid state sensors
charged couple device (CCD)
complimentary metal oxide semiconductor (CMOS)
Describe solid state sensors
connected to computer - usually wired but can be wireless
latent image created and immediately read within the sensor itself meaning final image is created virtually instantly
What are the components of a solid state sensor
black housing + cable
electronic substrate
CMOS imaging chip
fibre-optic face plate
scintillator screen
front housing
direction of the x ray beam
What is the point of the identification dot
it is located in the corner of the receptor to aid orientation of the image
only effective if the receptor was positioned correctly during exposure
How is cross infection control done for digital receptors
intra oral receptor have purpose made single use covers to prevent saliva contamination
What are examples of cross infection control covers
adhesive sealed plastic covers
long plastic sleeves
Why do receptors require careful handling
both digital and film receptors can be damaged
for digital, if certain types of damage happen they will impact every subsequent image obtained from that receptor and this reduces their diagnostic value and may render the receptor unusable
How should receptors be handled to prevent damage
hold it by their edges, not by their fault surface
What are types of damage you can get
scratches and tears
fingerprints
bending and creases
What are the features of phosphor plates
thinner, lighter and flexible
wireless so mores table and comfortable
variable room light sensitivity meaning there is risk of an impaired image
latent image needs to be processed in scanner separately
handling similar to film
What are the features of solid state sensors
bulkier and rigid
usually wired
smaller active area for same physical area of recpetor
no issue with room light control
arguably more durable and so they’re replaced less often
more expensive
What are the components of an inter oral film packet
Inner paper dental film inner paper wrap lead foil backing outer package
What is the function of the protective paper surrounding the film
it protects the film from light exposure, damage by fingers and saliva
What is the function of the lead foil in the intra oral film packet
it absorbs some excess x ray photons
What is the function of the outer wrapper
it prevents ingress of saliva
indicates which side of the packet is in the front
What is radiographic film
material in which the actual image is formed
sensitive to both x ray photons and visible light photons
photons interact with emulsion on film to produce latent image which only becomes invisible after chemical processing
What is the structure of radiographic film
transparent plastic base on inside
adhesive surrounding
emulsion on top
protective coating of clear gelatin
What is the function of a transparent plastic base
supports the emulsion
What is the function of the adhesive
attaches the emulsion to the plastic base
Where is the emulsion
layered on both sides of the plastic base
What is the function of the protective coating of clear gelatin
shields the emulsion from mechanical damage
What is radiographic emulsions made of
it is silver halide crystals embedded in gelatin binder
crystals are microscopic and they are what become the pixels of the final image
What are the silver halide crystals
usually silver bromide
they become sensitized upon interaction with x-ray (& visible light) photons
What happens to silver halide crystals during processing
the sensitized crystals are converted to particles of black metallic silver and these lead to the dark parts of the image
the non sensitized crystals are removed resulting in the lighter parts of the image
Where is the lead foil seen
it lies behind the film and absorbs photons behind the primary beam and also x ray photons that scatter in the patient smooth and bounce back to hit the film
What can be seen if the receptor is put back to front
you see a embossed pattern as the x ray photons have to pass through the lead before the emulsion
What is film speed
relates to the amount of x ray exposure required to produce an adequate image
What does increased film speed mean
increased speed means reduced radiation required to achieve an image
What is film speed affected by
number and size of the silver halide crystals
larger crystals have a faster film but poorer image quality
If you change to a different film speed what must u do
convert settings on x-ray unit which has to be done by a qualified technician
install a filter to absorb part of the primary x ray beam
What are intensifying screens
used alongside special indirect action film for extra oral radiographs
too bulky fr intra oral use
REDUCE RADIATION DOSE BUT ALSO REDUCE DETAIL
Describe how intensifying screens work
the film is placed inside the cassette with an intensifying screen on either side
the screens release visible light upon exposure to x ray and this visible light creates latent image on film which can be converted using film processing
What is film processing
sequence of tests which converts the invisible latent image to a visible permanent image
Where must film processing be carried out
must be carried out under controlled standardized conditions to ensure consistent image quality
What are the different methods for film processing
manual
automated
self developing films
What are the common steps for film processing
developing washing fixing washing drying
What happens in developing
converts sensitized crystals to black metallic silver particles resulting in darker areas
What happens in washing
removes residual developer solution
What happens in fixing
removes non sensitized crystals hardens emulsion (which contains the black metallic silver)
What happens in washing
removes residual fixer solution
What happens in drying
removes water so that the film is ready to be handled/stored
Describe what happens in the manual or wet cycle
person dips film into different tanks of chemicals at precise concentrations/temperatures for specific periods of time and washes the film after each tank
Where must the manual cycle be done
in a dark room with absolute light-tightness and adequate ventilation
What is the automated cycle
all necessary steps carried out within a machine
exposed film goes in one end and processed film comes out the other
What is the benefits and disadvantages of the automated cycle
faster and more controlled than manual processing and avoids need for a dark room
more expensive
In the automated cycle, how is the washing cycle done
sponge rollers squeeze developer solution of the film
How do you open a film packet for automated processing
disinfect the surface of the packet and wipe off
hold the packet under the hood of the processor unit
peel back flap of outer wrapper
fold back lead foil
pull back paper flip
hold film by edges (NOT SURFACES) and slide out
insert film into processor slot/shelf
What are the advantages of self developing films
no darkroom or processing facilities required
faster
What is the disadvantage of self developing films
poor image quality - important
image deteriorates more rapidly over time
no lead foil - important
easily bent
difficult to use in positioning holders
relatively expensive
What are processing issues in developing
it involves a chemical reaction (sensitized silver halide crystals -> black silver)
reaction affected by time, temp and solution conc
developer solution oxides in air - becomes less effective over time, needs to be replaced regularly (irrespective to how many films have been developed)
What are the potential causes of pale image
exposure issue
developing issue
What are exposure issue that can lead to a pale image
radiation exposure factors too low
What are developing issues that can lead to a pale image
film removed from solution too early
solution too cold
solution too dilute/old
What are issues that come form inadequate fixing
means non desensitised crystals are left behind
image is greenish-yellow or milky
image becomes brown over time
What are issues that come from inadequate washing
developer and fixer solution will continue to act if not washed off
What are issues with film storage
takes up room
needs to be easily accessible and safe from damage
requires a reliable organization system to allow images to be found easily and reduce risk of images being lost and mixed up
What are advantages of digital radiography
no need for chemical prcoesinsg
easy storage and archiving of iamages
easy back up of images
images can be integrated into patients records if digital
easy transfer/sharing of iamges
images can be manipulated
What are disadvantages of digital radiography
worse resolution and risk of pixelation
requires diagnosis level computer monitors for optimal viewing
risk of data corruption / loss which is solved by backing up
hard copy print outs have lower image quality
image enhancement can create misleading images
