Quality Assurance - Common film and digital faults Flashcards
describe pale/weak image
- incorrect exposure selected - not enough radiation = underexposed image
- film did not spend enough time in the developer tank
- the developer may be exhausted or at a very low temperature
- chemicals not diluted correctly
Incorrect exposure factor selection on a phosphor plate?
speckled white areas have just not had any exposure to radiation, so the phosphor crystals cannot emit light, because no interaction with radiation has occurred. Consequently, there is no information for the computer software to convert into a shade of grey from those pixels
Describe incorrect film size
A size 2 has been used for anterior teeth, it should always be a size 0. There is also collimation along 2 edges which means the tube is not sitting with all 4 corners touching the guide ring. The film is also damaged with several scratches and marks, and it is under exposed
How can you prevent pale and weak images?
- Following quality assurance programme can prevent these faults
- use sensitometry testing and log routine processor maintenance
- important to always select the correct exposure factors
- regularly checking x-ray tube output
- topping up developer when required
describe fogged film
area of fogging down the left-hand side. This means the film has either been exposed to light leakage before it has been exposed through incorrect storage, or it has been handled wrong during processing, possibly from light leaking into the glove box of the processor. The image itself is not good as the teeth are quite elongated and the apices are missing as a result. This is caused when the vertical angulation of the tube or film is wrong
Describe second fogged film
This image is also fogged along the bottom of the film over the crowns. This image is also likely affected by movement artefact- image is quite blurred suggesting that the patient has moved during the exposure
What are fogging prevention?
- good QA programme in place
- carrying out the coin test regularly in glove boxes and under the safelight
- ensuring that open boxes of films are stored correctly
- staff are appropriately trained
describe dark image
- Too high of an exposure will give a dark image
- if not exposure, then likely processing fault
- film spent too long in the developer tank
- temperature of developer too high
- developer not diluted enough when it was changed
how can dark image be prevented?
- routine maintenance of the processor
- regular checking of the developer temperature
- having a robust QA programme
- regular staff training
describe green/yellow tinted film
This is caused by insufficient fixing during processing, time temperature or dilution. Similar reasons as mentioned above
As mentioned above, problems like these are eliminated by taking care of your processor and topping up fixer when required
describe pattern
This pattern has been caused by chemicals not being properly washed from the film during processing. Other splash marks to look out for are dark spots caused by developer splashes and clear spots caused by fixer splashes.
Again, appropriate processor maintenance is the key to preventing this and making sure the water in the wash tank is regularly changed.
describe static electricity pattern
This interesting pattern has been caused by static electricity discharging on the film. It often resembles a lightning strike or a tree. It can be caused when a film is pulled quickly from the packet when the atmosphere is dry.
It can be prevented by making sure the darkroom is well ventilated and film is stored/handled correctly
describe image
This image has been produced on a solid-state sensor -the curved marks on the bottom left corner are damaged pixels on the sensor resulting in artefact. There is also an area where no x-rays have reached the sensor where the 8 is overlying the oblique ridge on the mandible. The combined densities of the structures have absorbed all the radiation and prevented a reaction occurring with the pixels in the sensor.
describe phosphor plate image
The white line artefact is a speck of dust on the sensor in the processing tower which has blocked the transfer of data from one line of pixels.
Faults of these types are prevented by careful handling of digital equipment. Any scanners or processing towers should be regularly maintained by service engineers, and phosphor plates and sensors should be scanned monthly and checked for damage. The results of which should always be recorded in your QA programme.
Image is of the phoshpor plate that is damaged in these images and should no longer be used
Images like those on the right are regularly sent from dental partitioners. As well as the multitudes of scratches, the edges of the plate are starting to delaminate. On the occlusal view the marks are slightly more subtle, but submandibular occlusals are usually taken for salivary gland stones so artefacts on the film are not ideal as they may be mistaken for pathology.
describe DPT image
This DPT image has scratches and marks overlying the anatomy.
Little dots on the lower left 3 and inferior to the lower left 4.
May be a film artefact, or the patient works in a sheet metal factory, garage or welding and has been exposed to high velocity specs of metal. Looking at the image it is unclear whether the dots are foreign bodies in the patient or artefacts caused by poor film handling or dust inside the cassette.
describe image
Images taken on damaged phosphor plates
Exposing plates to extreme changes in temperature will damage the phosphor layer and prevent it from functioning correctly.
describe faults on image
Film packet back to front – foil marks visible. The lead foil has partially absorbed the x-ray photons giving an under exposed image.
Not acceptable.
describe faults on image
Crimp marks – Nail marks and scratches on the film emulsion due to poor handling.
Not acceptable.
describe faults on image
Wrong size of receptor used.
Not acceptable.
describe faults on image
Bone levels missing due to collimation. Not acceptable.
describe faults on image
Corner of film bent over, cusps separated and teeth slightly elongated. Just acceptable.
describe faults on image
Bisecting angle technique elongated and no apex on film. Not acceptable.
describe faults on image
Glasses on film. Brown tinge from incorrect fixing. Not acceptable.
describe faults on image
Glasses on film causing image artefact. Patient position not great, chin slightly high. Just acceptable.
describe faults on image
Double exposed film. (Used twice).
Not acceptable.
describe faults on image
Digital sensor cable in front of sensor causing artefact.
Not acceptable.
describe faults on image
2 positioning faults - frankfurt plane not parallel to the floor and chin too far down. Patient is rotated, uneven molar sizes. Not acceptable.
describe faults on image
Film has a big bend across the middle and nail marks in the emulsion, image blurred from patient movement. Not acceptable.
describe faults on image
Central air shadow from tongue not being against the palate.
Earrings not removed, ghosting.
Narrow incisors from patient being too far into the machine.
Not acceptable.
describe faults on image
Face mask pulled down under chin and metal strip in nose bar causing artefact.
Acceptable as no detriment to image.
