How do you create an x-ray image? Flashcards
how does film-based imaging work?
Films were directly exposed by X-rays and then developed to produce the image. These developed films will be placed in a light box and then these images are then viewed.
how a film-based images processed?
Silver bromide crystals within the film become sensitised when in contact with X-rays or visible light. Then this film is removed from the patient’s mouth. This film is dipped in various chemicals in order to become developed to produce the greyscale image.
why is digital imaging used now rather than film-based imaging?
Less likely to get images that are over or under exposed and less like to get an image that is too dark or too light.
what are the 2 types of digital imaging?
solid state receptors
phosphor plate receptors
what are solid state receptors?
They are semiconductors.
They contain CCD (charged couple device) sensors
CMOS (complementary metal oxide semiconductors) sensors, the plate is exposed and the image is directly produced. they produce an image very fast.
what are the disadvantages of the solid state receptors?
they are bulkier and difficult to position in the mouth, some include a wire which will hang out of the patient’s mouth.
what are the components of the solid state receptors?
backhouse and cable
electronic substrate
CMOS imaging chip
fibre optic face plate
scintillator screen
front housing
what are the phosphor plate receptors?
The phosphor plate indirectly produces an image. It is wireless and has to be placed in a processor unit for an image to be produced.
what are the advantages of the phosphor plate?
Comes in various different sizes
very flexible so easily positioned in patients’ mouths
reuseable
cheaper
what are the disadvantages of the phosphor plate?
They are not attached to a computer they capture a latent image, which needs to be placed in a processor and then scanned by a laser beam from there an image is produced.
How is the phosphor plate processed?
The phosphor plate has a magnetic layer which is how it is pulled into the reader. The plate is scanned and cleared using white light and then ejected.
what is the pixel size for phosphor plate imaging?
60um
The smaller the pixel size the higher the spatial resolution.
what is the pixel size for solid state imaging?
20um
How many greyscale values do we have?
242
what are the advantages of digital imaging?
You can post-process the image by adjusting the contrast and brightness of the image. Also can avoid over and under exposed images
Lower dose radiation
No chemical processing, reducing processing artefacts
Rapid image producing
Digital storage reduces paper storage and easily share images
Images can be easily magnified and software tools can aid in measurements
