Image Receptors Flashcards
The item the x-ray image is formed on
Image receptor
Give three examples of image receptors
Film, plate or digital sensor
What is meant by ‘ fogging of the film’?
When some photons do not have enough energy to make a useful interaction with the receptor, therefore resultant scatter of photons can degrade the image.
What are the two ways to capture an x-ray image?
Film or digital
What are the two types of film image receptors that can be used?
direct action film
indirect action film
What are the two types of digital image receptors?
-solid state sensor
- photo-stimulate phosphor (PSP)
What image receptor is described:
An actual piece of film which is sensitive to x-rays that is wrapped in a packet.
used intra-orally, x-ray directly acts on silver halide crystals in film emulsion
Direct film
What image receptor is described:
a film inside a cassette which contains intensifying screens, that x-ray photons interact with to produce light photons, exposing the film to produce the image.
used extra-orally, light from intensifying screens act on silver halide crystals in film emulsion
Indirect film
What image receptor is described:
Two types of sensors:
- CCD and CMOS
These work by converting light into electrons
Solid state sensor
What does CCD stand for?
Charge-coupled device
What does CMOS stand for?
Complimentary metal-oxide semiconductor
What image receptor is described:
Latent image produced by the interaction of x-rays with the phosphor layer on the plate, which is then scanned by a laser to produce an image.
Phosphor- stimulable phosphor (PSP)
which digital sensor can sometimes not be tolerated well by patients, due to it’s large and bulky nature?
Solid state sensors
Which digital sensor has better image resolution?
Solid state sensors
What are the two sides of a phosphor plate?
Phosphor coating side ( white)
Black side with orientation dot
which side of a phosphor plate is the image formed on?
Phosphor coating side ( white)
what side of the phosphor plate should be visible through the window of a protective bag?
The black side
Describe the stable excited state
Image plate placed in patients mouth and phosphor coating is exposed to x-rays which causes a reaction within the phosphor.
Describe the unstable excited state
The plate is dropped into the vista scan unit where it is scanned by a red laser
What type of light is emitted to be differed into an image once the phosphor plate is scanned by red laser?
Blue light
What are the 4 layers that make up a charge couple device? And what is their function?
front cover
scintillator layer (converts x-ray energy to light)
silicon layer ( converts light into electrical signal)
back cover ( incorporates a cable to carry signal to pc)
What is a ‘pixel’?
Electrons within each cell
What is the difference between CCD and CMOS?
CMOS - signals sent from each individual cell (pixel)
CDD- signals sent from lines of cells (pixels)
What is the issue with digital images?
There is no orientation dot visible on the image. This means you may have images that could be very east to turn the wrong way and get muddled up.
What type of solid state sensor has higher quality image production?
CCD
Name 6 reasons why digital image receptors would be chosen over film?
No chemicals
Faster processing times
Easy archiving
Easy image transfer
Image manipulation
Dose reduction
In regards to the resolution of an image, what happens in response to shorter exposure of image?
A drop in image resolution
What size would a pixel be to make an image less detailed?
Large
What happens to exposure if there is too much radiation?
High exposure and image appears dark
What happens to exposure if there is not enough radiation?
Low exposure and the image appears pale
What does PACS stand for?
Picture archiving and communication system
What are the different sizes of receptor for digital PSP’s?
0,1,2 and 4
What is the one available size of solid state receptor?
2
Why might using a size 2 solid state receptor make x-raying anterior teeth difficult?
Due to large size of receptor and subsequent positioning in the mouth
What does the plastic barrier wrapped around film do?
Protects film from saliva and is good for infection control
How many layers are there in a direct action film packet?
4
What are the 4 layers in a direct action film packet?
Outer plastic wrapping
Block paper
Lead foil
Film
Which layer of direct action film:
Keeps film dry, protects it from fogging and indicates the correct orientation of the film inside the mouth?
Outer plastic wrapping
Why can you only open film packet in a dark room under a safe light?
Because radiographic film is photosensitive, which means it will react with light
Which layer of direct action film:
Protects films for light leakage and stiffens/ supports the film to prevent crimp/pressure marks appearing?
Black paper
Which layer of direct action film:
Is composed of a mixture of lead and aluminium, readily absorbs x-rays, prevents back scatter and has a distinct pattern embossed into lead?
Lead foil
Which layer of direct action film:
Is composed of a mixture of lead and aluminium, readily absorbs x-rays, prevents back scatter and has a distinct pattern embossed into lead?
Lead foil
Which layer of direct action film:
Is composed of: base layer, adhesive layer (with anti-glare tint), followed by double emulsion layers and gelatin protective layer?
Film
What layer of film reacts with x-rays to form an image?
Emulsion layer
What layer of film reacts with x-rays to form an image?
Emulsion layer
What components make up the emulsion layer of film?
Silver halide crystals suspended in gelatin
What are the two functions of gelatin?
allows even distribution of crystals
absorbs liquid readily to allow processing
what is the function of the adhesive layer of film?
Sticks the emulsion to the base layer
How is a direct action “latent image” formed?
X-ray photons hit silver halide crystal emulsion of film. Silver halide crystal becomes sensitised, this is known as the LATENT IMAGE.
The pattern produced within the emulsion by the sensitising of silver bromide/iodide crystals, either by light or x-rays.
Latent image
What is the main reaction involved in creating a latent image?
The reduction of the silver bromide crystals to black metallic silver
What are the two available speeds of film?
Slow and fast
What other term can be used for ‘speed of film’?
Sensitivity of film to x-rays ( the exposure required to produce a given amount of blackening on an image)
What is the effect on film speed, the larger the crystal?
The faster the film speed
What is the sensitivity of the film dependant upon?
The size of crystals in the emulsion
If the film speed is fast, is the amount of x-rays required to produce an image higher or lower?
Lower
How does indirect film differ from direct film?
It is sensitive to light rather than x-rays
What are the four layers that comprise intensifying screens?
base layer
reflective layer
phosphor layer
supercoat
What material makes up the base layer of intensifying screens?
Polyester
What material makes up the base layer of intensifying screens?
Polyester
what is the purpose of the reflective layer of intensifying screens?
Reflects light produced back towards film
What is the function of the phosphor layer in an intensifying screen?
Contains fluorescent phosphors with emit light when excited by X-rays
What is the purpose of the super coat layer of intensifying screens?
Protects phosphor layer from damage
What do intensifying screens allow for?
A reduction in exposure and therefore a reduced dose to patient
The reduction of the exposed silver bromide crystal to black metallic silver and then making the image permanent is known as?
Film processing
The reduction of the exposed silver bromide crystal to black metallic silver and then making the image permanent is known as?
Film processing
what are the three methods of film processing?
Automatic
Manual
Instant
Which type of film processing only tends to be done in emergency situations as it is unreliable?
Instant film processing
What are the five stages of film processing?
Develop
Wash
Fix
Wash
Dry
What occurs in the develop stage of film processing?
Makes latent image visible
What occurs in the two wash stages of film processing?
( after develop stage) Stops development by removing excess developer from film
(after fix stage) Stops fix and removes residual fixer
What happens in the fix stage of film processing?
Makes image permanent
What happens in the dry stage of film processing?
Makes film easier to handle and prevents damage
What are the two developing agents that act upon silver halide crystals, sensitising them by chemical reduction of silver bromide to silver + bromide?
Phenidone and hydroquinone
What are the two developing agents that act upon silver halide crystals, sensitising them by chemical reduction of silver bromide to silver + bromide?
Phenidone and hydroquinone
What is the activator within the developer that controls the activity of developing agents?
Calcium carbonate
What is the restrained within the developer that stops the developer working on unexposed crystals?
Potassium bromide
What is the preservative within the developer that slows down oxidation?
Sodium sulphite
What is the solvent within the developer that dilutes the chemicals?
Water
What is very important to note about working temperatures of developers?
Each developer has its optimum working temperature
What is the action of the developing agent on silver halide crystals dependent on?
Time
Temperature
Concentration
What is the action of the developing agent on silver halide crystals dependent on?
Time
Temperature
Concentration
If the film stays in developer too long, how will it appear?
Dark
If the film stays in developer too short, how will it appear?
Light
If the film is too hot, how will it appear?
Dark
If the film is too cold, how will it appear?
Light
If the film is too concentrated, how will it appear?
Dark
If the film isn’t concentrated enough, how will it appear?
Light
How will silver halide crystals which are developed but not fixed appear?
Black
What is the role of fixing agents?
Change unexposed silver halide to soluble compound so they can be washed away
What maintains the pH and neutralises the developer?
Acid
What are the 5 components of fixer stage of film o processing?
Clearing agent (ammonium thiosulphate)
Acidifier (acetic acid)
Hardener (aluminium chloride)
Preservative (sodium sulphite)
Solvent (water)
What happens to unexposed silver halide crystals during fixing?
They are removed
How will under-fixed images appear?
They will have a green tinge and will not archive well
What is the difference between a manual wash and an automatic wash of the film?
Manual wash occurs between develop stage and fix stage and then between fix stage and dry stage. Whereas, automatic wash only occurs between fix stage and dry stage.
What is the purpose of washing the film?
Removes unexposed silver halide crystal once made soluble by fixer
What will the effect of insufficient washing do to the film?
Make film feel sticky and look cloudy
Which method of film processing is the best?
Automatic film processing
When would instant film processing be beneficial?
If you have to process images away from a power source
What is the main regulation used for health and safety when carrying out radiographs?
COSHH
What does COSHH stand for?
Control of substances hazardous to health
What work act meant that employers has a legal duty to ensure their staffs were safe and risk free at work?
HEALTH AND SAFETY AT WORK ACT 1974
What must manufactures supply for potential hazardous substances that makes you aware of how dangerous your developer and fixer are?
Material safety data sheets
