Digital & Film Radiography Flashcards
What are the different types of digital receptor?
- phosphor plate
- solid state sensor
- all multiple use
What are the different types of film receptor?
- direct action film
- indirect action film
- all single use
What are the 3 different sizes of phosphor plates and what are they used for?
- size 0
- anterior periapicals
- size 2
- bitewings
- posterior periapicals
- size 4
- occlusal
What values given to x-ray intensity create black and white on a receptor?
- 0 = black
- 255 = white
What are the advantages and disadvantages of increasing the number of pixels on a digital radiograph?
- advantages
- better detail
- higher resolution
- disadvantages
- more storage space required
- increased cost
- manufacturing challenges concerning smaller pixels
What is the typical greyscale bit depth?
- 8 bits
- 256 shades of grey
- 8 bit is the minimum
What is the format for digital images?
- DICOM
- digital imaging and communications in medicine
- also stores patient ID, exposure settings, date of image
- international standard for handling digital medical images
- used to transmit, store, retrieve, print, process and display
- works between different software, machines, hospitals
How are digital images managed?
- PACS
- picture archiving and communication system
- medical imaging technology
- provides storage and access to images
- input by imaging modalities
- secure network for transmission of patient information
- workstations for interpreting and reviewing images
- archives for the storage and retrieval of images/reports
- vary in size and scale
- hospital PACS are not connected to dental practices
In what ways can digital radiographs be altered?
- contrast/windowing
- darker areas darker
- lighter areas lighter
- negative
- flipping covers
- emboss
- makes areas of contrast stand out
- magnify
- focus on area of interest
How should digital radiographs be viewed?
- environmental
- subdued lighting
- avoid glare
- monitor
- clean
- adequate display resolution
- high enough brightness level
- suitable contract level
What is SMPTE test pattern?
- society of motion picture and television engineers
- available online
- used to assess resolution, contrast and brightness of monitor
What are phosphor plates?
- also called:
- photostimulable phosphor plate
- storage phosphor plate
- not connected to computer
- after receptor is exposed to x-rays it must be put in a scanner
- read to create the final image
How are images created using phosphor plates?
- within patient’s mouth
- receptor exposed to x-ray beam
- phosphor crystals in receptor excited by x-ray
- creation of latent image
- within scanner
- receptor scanned by a laser
- laser energy causes excited phosphor crystals to emit visible light
- light is detected and creates digital image
What are solid-state sensors?
- two types
- CCD (charge-coupled device)
- CMOS )complimentary metal oxide semiconductor)
- connected to computer
- usually wired
- some wireless now available
How are images created using solid state sensors?
- latent image created
- immediately ready within sensory
- final image created virtually instantly
What are the components of solid-state sensors?
- back housing and cable
- electronic substrate
- CMOS imaging chip
- fiberoptic faceplate
- scintillator screen
- front housing
What are identification dots?
- located in corner of receptor to aid orientation of image
- helps with orientation of image
- ensures image has not been flipped
- only effective if receptor was positioned correctly during exposure
- should be on the top right or left
How is cross-infection control managed in digital radiography?
- intra-oral receptors have purpose made covers to prevent saliva contamination
- single-use covered
- phosphor plates
- adhesive sealed plastic covers - solid state sensors
- long plastic sleeves - receptors additionally disinfected between uses
How is cross-infection control managed in digital radiography?
- intra-oral receptors have purpose made covers to prevent saliva contamination
- single-use covered
- phosphor plates
- adhesive sealed plastic covers - solid state sensors
- long plastic sleeves - receptors additionally disinfected between uses
What digital receptors are used for extra-oral radiology?
- larger phosphor plates
- larger solid state sensors
- usually build into machine
What digital receptors are used for extra-oral radiology?
- larger phosphor plates
- larger solid state sensors
- usually build into machine
How should receptors be handled?
- held by edges
- not flat surfaces
What are common types of damage to receptors?
- scratches
- tears
- fingerprints
- bending
- creasing
What are common types of damage to receptors?
- scratches
- tears
- fingerprints
- bending
- creasing
Compare phosphor plates and solid state sensors
- phosphor plates
- thinner, lighter and usually flexible
- wireless, more stable and more comfortable
- variable room-light sensitivity
- risk of impaired image
- latent image needs to be processed in scanner
- handling similar to film
- solid state sensors
- bulkier and rigid
- usually wired
- smaller active area for same physical area of receptor
- no issues with room-light control
- arguably more durable
- replaced less often
- more expensive
What does an intra-oral film packet contain?
- inner paper
- dental film
- inner paper wrap
- lead foil backing
- outer package
What is the function of protective paper in intra-oral film packets?
- protects film
- light exposure
- damage by fingers
- saliva
What is the function of lead foil in intra-oral film packets?
- lies behind film
- absorbs some excess x-ray photons
- primary beam continuing past the film
- scattered by patient’s tissues, returning back to film
- embossed pattern to highlight if receptor was placed wrong way round
- texture shown on image
- image will also be pale
What is the function of the outer wrapper in intra-oral film packets?
- prevents ingress of saliva
- indicates which side of the packet is the front
What are the properties of the radiographic film in an intra-oral film packet?
- material in which the actual image is formed
- sensitive to both x-ray photons and visible light photons
- photons interact with emulsion on film
- produces latent image
- only visible after chemical processing
- structure
- transparent plastic base
- supports the emulsion - adhesive
- attaches emulsion to plastic base - emulsion
- layered on both sides of plastic base - protective coating of clear gelation
- shields emulsion from mechanical damage
- transparent plastic base
What is the emulsion of a radiographic film made of and how does it work?
- silver halide crystals embedded in a gelatine binder
- usually silver bromide
- microscopic crystals that become ‘pixels’ of image
- become sensitised upon interaction with x-ray photons
- sensitised crystals converted to particles
- black metallic silver
- dark parts of final image - non-sensitised crystals removed
- light parts of final image
- sensitised crystals converted to particles
What is film speed?
- relates tp the amount of x-ray exposure to produce an adequate image
- higher the speed, the less radiation required to achieve an image
- affected by number and size of silver halide crystals
- larger crystals require a faster film
- poorer image quality
- larger crystals require a faster film
How are film speeds adjusted?
- qualified technician converts settings on x-ray unit
- filter installed to absorb part of primary x-ray beam
- prevents over-exposure
What are intensifying screens?
- used alongside special indirect action films for extra oral
- too bulky for intraoral use
- recude radiation dose
- also reduce detail
- excitation within screen disperses energy
- also reduce detail
- screens release visible light to create latent image on film
What is film processing?
- sequence of steps which converts the invisible latent image to a visible permanent image
- must be carried our under controlled, standardised conditions to ensure consistent image quality
What are the different methods of film processing?
- manual
- automated
- self-developing film
What are the common steps in film processing?
- developing
- converts sensitised crystals to black metallic silver particles
- washing
- removes residual developer solution
- fixing
- removes non-sensitised crystals
- hardens emulsion (contains black metal silver)
- washing
- removes residual fixer solution
- drying
- removes water so film can be handled and stored
What is the manual cycle?
- person dips film into different tanks of chemicals
- precise concentrations and temperatures
- specific periods of time
- washes film after each tank
- must be carried out in dark room
- adequate light-tightness (red light)
- adequate ventilation
What is the automated cycle?
- all necessary steps carried out in machine
- faster and more controlled than manual processing
- avoids need for dark room
- more expensive
- 4 compartments
- developer
- fixer
- wash
- dryer
- sponge rollers squeeze developer solution out of film
- instead of washing with water
How are film packets opened for automated processing?
- disinfect surface of the packet
- hold the packet under the hood of the processor unit
- peel back flat of outer wrapper
- fold back lead foil
- pull back paper flap
- hold film by edges and slide out
- insert film into processor
What are self-developing films?
- radiographic film and processing solution in same packet
- squeeze solution into film once exposed
- not recommended
- advantages
- no dark-room or processing facilities required
- faster
- around 1 minute
- disadvantages
- poorer image quality
- no lead foil
- image deteriorates more rapidly over time
- easily bent
- difficult to use in positioning holders
- relatively expensive
Why can developer solution cause issues?
- developer solution oxidises in air
- becomes less effective over time
- needs to be replaced regularly
- irrespective of how many films have been developed
What are potential causes of a pale image?
- exposure issue
- radiation exposure too low
- developing issue
- film removed from solution too early
- solution too cold
- solution too dilute/old
What are the potential causes of a dark image?
- exposure issue
- radiation exposure too high
- developing issue
- film left in solution too long
- solution too warm
- solution too concentrated
What issues can arise as a result of inadequate fixing?
- inadequate fixing means non-sensitised crystals are left
- image greenish-yellow or milky
- image becomes brown over time
What issues can arise as a result of inadequate washing?
- developer and fixer will continue to act if not washed off
What are the challenges of film storage?
- takes up room
- needs to be easily accessible and safe from damage
- requires a reliable organisation system
- allows images to be easily found
- reduces risk of images being lost/mixed up
Compare digital and dilm radiography
- advantages of digital radiography
- no need for chemical processing
- easy storage and archiving of images
- easy back-up of images
- images can be integrated into patient records
- easy transferring/sharing of images
- images can be manipulated
- disadvantages of digital radiography
- worse resolution/risk of pixelation
- requires diagnostic-level computer monitors to optimally view
- risk pf data corruption/loss (solved by backing up)
- hard copy print outs generally have reduced image quality
- image enhancement can create misleading images
