Digital and Film Radiology Flashcards
What is the plate made from in digital X-Ray receptors?
How do these create the final image?
Phosphor Plate
After receptor is exposed to x-rays, it must be put in a scanner and read to create the final image
What type of X-rays receptor can be used again?
What type can’t?
Digital receptors can be disinfected and used again
Film receptors can’t be used again as they become the image themselves
What size of phosphor plate receptor is used for anterior periapicals?
Size 0
What size of phosphor plate receptor is used for bitewings and posterior periapicals?
Size 2
What size of phosphor plate receptor is used for occlusal radiographs?
Size 4
What creates an X-Ray shadow?
What is it?
When the x-ray beam passes through an object some of the photons are attenuated which creates an x-ray shadow
The x-ray shadow is the image ‘information’ held by the x-ray photons after an x-ray beam has passed through an object
The image receptor detects this x-ray shadow & uses it to create an image
What is the benefit of a higher number of pixels?
More pixels means better detail in the image and a higher resolution
Increasing the resolution will provide a more diagnostic image up to a limit (eventually it will not provide any meaningful clinical benefit)
What does DICOM stand for?
What is it?
Digital Imaging & Communications in Medicine
International standard format for handling digital medical images (used to transmit, store, retrieve, print, process & display images)
What is the SMPTE test pattern?
What is it used for?
Society of Motion Picture & Television Engineers
Can be used to assess the resolution, contrast & brightness of your monitor/monitors
How is the image created in the patient’s mouth using phosphor plates?
Receptor is exposed to the x-ray beam
Phosphor crystals in receptor are excited by the x-ray energy, resulting in the creation of a latent image
How is the image created within the scanner using phosphor plates?
Receptor is scanned by a laser
The laser energy causes the excited phosphor crystals to emit visible light
The light is detected & creates the digital image
How does the phosphor plate receptor transfer the image to a computer?
Has to be wiped and disinfected and placed in a scanner
How do solid-state sensors transfer the image to the computer?
Usually wired to the computer but can be wireless
Latent image created & immediately read within the sensor itself (final image is created virtually instantly)
Where does the identification dot need to be placed when putting together an X-ray receptor?
In the top right hand corner
What are the advantages of phosphor plates?
Thinner, lighter and more flexible
Wireless, more comfortable
Variable room light sensitivity & risk of impaired image (need to be in a dark box)
Latent image needs to be processed in scanner separately
Handling similar to film
What are the advantages and disadvantages of solid-state sensors?
Bulkier and rigid
smaller active area (for same physical area of receptor)
more durable- replaced less often
no issues with room-light control
more expensive
What is in an intra-oral film packet? (Used in film radiography)
Protective (black) paper
—Protects film from light exposure, damage by fingers and saliva
Outer wrapper
—prevents ingress of saliva
—indicates which side of the packet is the front
Lead Foil
—absorbs some excess x-ray photons
What is a radiographic film? What photons is it sensitive to? How does this produce an image?
Material in which the actual image is formed
sensitive to both x-ray photons & visible light photons
photons interact with emulsion on film to produce latent image which only becomes visible after chemical processing
What is in a radiographic film structure?
Transparent plastic base
Adhesive
Emulsion
Protective coating of clear gelatin
What is the transparent plastic base for in radiographic film structure?
To support the emulsion
What is the adhesive for in radiographic film structure?
Attaches the emulsion to the plastic base
What is the emulsion for in radiographic film structure?
It is layered on both sides of the plastic base
Silver halide crystals embedded in a gelatin binder
Results in higher resolution than digital
What is the protective coating of clear gelatin for in radiographic film structure?
Shields the emulsion from mechanical damage?
How do the silver halide crystals produce an image in film radiography?
Become sensitised upon interaction with x-ray (& visible light) photons
During processing the sensitised crystals are converted to particles of black metallic silver (dark parts of final image)and the non-sensitised crystals are removed (light parts of the final image
What is film speed? What happens if you increase speed
Relates to the amount of x-ray exposure required to produce an adequate image
Increasing the speed decreases the radiation required to achieve an image
It is also affected by the number & size of the silver halide crystals (larger crystals= faster film but poorer image quality)
What must you do if changing to a different film speed?
Convert settings on x-ray unit (by a qualified technician)
or
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
They reduce radiation dose but also reduce detail
Why is film processing required for x-rays?
Converts the invisible latent image to a visible permanent image
What are some common steps in Film processing?
What does each step do?
Developing
–converts sensitised crystals to black metallic silver particles
Washing
–removes residual developer solution
Fixing
–removes non sensitised crystals and hardens the emulsion
Washing
–removes residual fixer solution
Drying
–removes water so film is ready to be handled/stored
What is involved in a manual (wet) processing cycle?
Person dips film into different tanks of chemicals at precise concentrations/temperatures for specific periods of time
Washes the film after each tank
Must be carried out in a dark room with light tightness and adequate ventilation
What are the steps for opening a film packet for automated processing?
Disinfect the surface of the packet (&wipe off)
Hold the packet under the hood of processor unit
Peel back flap of outer wrapper
Fold back lead foil
Pull back paper flap
Hold film by edges (not surfaces) and slide out
Insert film into processor
What are some developing issues during processing?
It involves a chemical reaction (between sensitised silver halide crystals and black silver)
Reaction affected by time, temperature and solution concentration
Developer solution oxidises in the air
–Becomes less effective over time
–Needs to be replaced regularly (irrespective to how many films have been developed)
What are some fixing issues during processing?
Fixing involves a chemical reaction which removes non-sensitised crystals & hardens the remaining emulsion
Inadequate fixing means non-sensitised crystals are left behind
–makes the image green/yellow ish or milky
–makes the image brown over time
What can cause a pale image to be formed?
Exposure issue
–radiation exposure factors too low
Developing issue
–film removed from solution too early
–solution too cold
–solution too dilute/old
What are the advantages to digital radiography?
No need for chemical processing
easy storage & archiving of images
easy back-up of images
images can be integrated into patient records
easy transfer/sharing of images
images can be manipulated
