Digital and Film Radiography Flashcards
what is the difference between film and digital radiography
they differ in how the x-ray beam acts after it interacts with the patient
digital radiography receptors are reusable whereas film are not
what x-ray receptors are used for digital radiography
phosphor plate
solid state sensor
what are the types of film receptors
direct action film
indirect action film
what size receptor is used for anterior periapicals
size 0
what size receptor is used for bitewings and posterior periapicals
size 2
what size receptor is used for bitewings and posterior periapicals
size 2
what size receptor is used for occlusal radiographs
size 4
what is an x-ray shadow
pattern of attenuation after passing through the object
how is x-ray shadow converted to a digital image
the receptor measures the x-ray intensity at defined areas (arranged in a grid) and then each wee box in the squarer is given its own value relating to x-ray intensity which then corresponds to a specific shade of grey
what are pixels
the grids of square in a receptor
each pixel can only display one coloiur
what gives a higher resolution
more pixels
why do we want a higher resolution
provides a more diagnostic image but only up to a limit
why can using more pixels potentially be a problem
when you increase pixels you increase storage size on computer which is increased costs
what is the greyscale depth
number of different shades of grey available
how many shades of grey are processed in radiographs
8 bits
what is the real number of shades available for radiography
256 (2 to the power of 8) goes from 0-255
what is a massive advantage of digital radiography
you can manipulate the image (make it bigger, rotate, change contrast)
what is embossing
contrast stands out more easier
how are digital images stored
DICOM - digital imaging and communications in medicine - universally acceptable
what other information is stored in DICOM
patient ID
exposure settings
date of image
how are digital images managed
PACs
picture archiving and communication system
what are not part of PACs
dental practices - you would need to email the dental hospital as a GDP to get them
what are the main components of PACs
input by imaging modalities
secure network for transmission of patient information
workstations for interpreting and reviewing images
what should the environment be like when viewing digital radiographs
subdued lighting
avoid glare
what is the SMPTE test pattern
something you can download from the internet asses the resolution, contrast and brightness of your monitor
what are the two types of digital intra-oral receptor
phosphor plates
solid state sensors
are phosphor plates connected to the computer
no
what is the process for using phosphor plates
after the receptor is exposed to x-rays it needs to be put in a scanner and read to create the final image
how are images created using phosphor plates
the receptor is exposed to an x-ray beam and the phosphor crystals in the receptor are excited by the x-rays resulting in the creation of the latent image
how are images created after the phosphor receptors are placed in the scanner
the receptor is scanned by a laser
the laser causes the excited phosphor crystals to emit visible light
light is detected and creates the digital image
what are the two types of solid-state sensors
CCD (charge coupled device)
CMOS (complimentary metal oxide semiconductor)
are solid state sensors connected to the computer
yes usually by a wire
how is the image created using solid state sensors
the latent image is created immediately and read within the sensor itself
what are the two disadvantages of solid state sensors
more expensive
more bulky
what is the identification dot
small dot which is on corner of receptor that will be on the actual radiograph and helps to re-orientate the image
hoe are intra-oral receptors protected by cross-infection control
they are concealed by single use covers to prevent saliva contamination
what happens to the receptor between uses
disinfected
what damage might scratches and tears appear as on an x-ray receptor image
white lines
what might bending or creasing a receptor cause in the final image
distortion
what are benefits of phosphor plates
thinner
lighter
usually flexible
wireless
what are the benefits of solid state sensors
more durable so you replace less often
no issues with room-light control
what is in the middle of the radiographic film packet
radiographic film
what is around the radiographic film
protective black paper which protects from light exposure, damage and saliva
what sits under the radiographic film
lead foil which absorbs some excess x-ray bea,
what covers the whole film packet
outer wrapper which protects from saliva
how do images process on x-ray film
the film is sensitive to x-ray photons and visible light photons and the photons interact with the emulsion on film to produce latent image which only becomes visible after chemical processing
what is the structure of a radiographic film
transparent plastic base
an adhesive that attaches emulsion to top and bottom of the plastic base
around which is a protective coating of clear gleatin
what are embedded in the emulsion layer
silver halide crystals embedded in a gelatin binder
what effectively become the pixels of the final film image
the silver halide crystals
why do film images give higher resolution than digital
as the silver halide crystals are microscopic and they are what work as the pixels
what occurs to the silver halide crystals when processing
they are converted into particles of black metallic silver which give the dark parts of final image and the non-sensitised crystals are removed which gives the light areas
what is the purpose of the lead foil in the film
absorbs excess x-ray photons - those in primary beam continuing past film and those scattered by patients tissues
how can you tell on film radiography if you have placed the receptor the wrong way round
the lead foil is embossed with a pattern which appears on the final image
what does film speed relate to
the amount of x-ray exposure required to produce an adequate image
what is film speed affected by
number and size of silver halide crystals
what does an increased film speed mean
decreased radiation required to achieve an image
what must you do if changing to a different film speed
convert settings on x-ray unit by a qualified technician
install a filter to absorb part of the primary x-ray beam
what are intensifying screens
you can reduce radiation dose but also get less detail
why is there less detail in intensifying screens
because the screen makes the photons spread out to a larger area so instead of a pinpoint accurate image they are larger
what are the different methods of film processing
manual
automated
self developing
what are the five steps of film processing
developing
washing
fixing
washing
drying
what occurs in the developing stage of film processing
converts sensitised crystals to black metallic silver particles
what occurs in washing stage of film processing
removes residual developer solution
what occurs in the fixing stage of film processing
removes non-sensitised crystals
hardens emulsion
what occurs in the second washing stage of film processing
removal of fixer solution
what occurs in the drying stage of film processing
removes water so film can be handled/ stored
what is the manual cycle
person dips film into different tanks of chemicals at precise concentrations and temperatures
what is the automated cycle
all necessary steps carried out in a machine
what are self developing films
longer cover on it, the chemicals are kept in one end are squeezed down to meet the film - but NOT recommended
what is the chemical reaction that turns sensitised silver halide crystals to black crystals controlled by
time
temperature
concentration
what might cause a pale image
exposure issue (too low)
developing solution (too cold, too old)
what is fixing
a chemical reaction which removes non-sensitised crystals and hardens remaining emulsion
what might show on an image if there has been inadequate fixing
the image will be greenish-yellow or milky
image becomes brown over time
how are film radiographs stored
reliable organisation system
advantages of digital radiography
no chemical processing
easier to store and archive
easy transferring and sharing of images
disadvantages of digital radiography
worse resolution
requires diagnostic level computer monitors
data corruption or loss
