Radiology Errors and Artefacts Flashcards
What checks must you do when taking a panoramic radiograph
- Select exposure factors & correct focal trough size
- Align patient within machine (Frankfort plane/midsagittal plane/canine)
- Check that the patient is standing with a straight spine & relaxed shoulders
- Ask patient to bite incisal edges on bite block
- Patient to stay still and place tongue against
palate - Check & expose
What checks must you do when taking an intra-oral radiograph
- Select correct sensor/film size
- Select correct holder and put together
correctly! - Select exposure settings
- Position sensor within mouth
- Align x-ray tube head
- Check & Expose
When looking at an image we analyse in relation to what 4 topics
- Preparation
- Positioning
- Processing
- Exposure
What are the 3 general things that you need to prepare before a radiograph
X ray area
Specific equipment
Patient
What needs to be prepared in the X ray area before a radiograph
- equipment
- computer acquisition systems
- patient chair & headrest
- processing equipment / phosphor plate scanners
What specific equipment needs to be prepared before a radiograph
- Intra-oral holders
- films/plates
- packets
- bite guides
- sterile covers
- cotton wool rolls
What about the patient needs to be prepared before a radiograph
- Identification
- explanation
- remove jewellery etc.
- position comfortably
Where should the sensing plate be relative to the ring that is used for aiming things
Right in the centre of the ring
Why might you see a straight line that shows no radioactive absorption when the plate isnt in the middle of the ring
Not because the ring is blocking it but because you’re probably using a rectangular collimator so you will have a rectangular radiation beam
What colour is the sensitive side of the phosphor plate
blue
What is the copper dot on the back of a phosphor plate for
If you put a phosphor plate in the wrong way around and the phosphor layer isnt facing the beam you will get an inverted image pretty much and this will make you think it you have scanned one side of the mouth when youve actually scanned the other.
So the copper dot is there to absorb radiation and will show up on the radiograph to tell you you’ve got it wrong
What is the small silver dot used for on a phosphor plate
This is a positiioning dot in the corner that should be placed in the holder so that it is towards the crown. It should be in the slot of the holder – DOT to SLOT !
How can there be edges on the radiograph that have not been exposed properly
- Ring not placed correctly
- Patient has moved it while in the mouth
- If ring is on and bad collimator alignment
- When we place in mouth can be difficult and moves
- Not placed firmly and al
What patient preparation do you need to do before a panoramic radiograph
- Remove all jewellery and appliances
- No Movement
- Tongue against palate
If the patient moves in a panoramic image what happens to the image
The entire image will become blurry
Why do we ask the patient to put their tongue against the palate
It blocks the airspace behind the tongue and stops a shadow forming over the upper anterior teeth.
Name some positioning faults you can have with intra-oral radiographs
- Not parallel- tube head and beam aiming device not aligned
- Not parallel – film not parallel with long axis of tooth
- Collimator not aligned with sensor/film (most often due to film/plate coming out of holder)
What happens to the image when the tube head and beam aiming device aren’t parallel
the beam wont go through the interdental spaces nicely and you get overlap between teeth
What can double exposure form in the radiograph
when someone has used the same plate twice and exposed it in the patients mouth before developing it, this cant happen on DR but can on CR
Describe the positioning ideal for taking a panoramic radiograph
- Standing with a straight spine
- Biting in the grooves of the bite block – not
too far forward or back - Head straight and median sagittal plane vertical – not rotated
- Frankfort plane horizontal - not “Chin Up” or “Chin Down”
If we dont line up a patient on the mid-sagittal plane what happens to the panoramic radiograph
can form an asymmetrical image and one side will appear alot thicker and just messed up
If we dont get the patient standing straight in a panoramic radiograph what happens to the image
The Spine is exacerbated in the radiograph and will see a white line showing in the image.
What happens if we dont line the patient up on the frankfurt horizontal plane
We lose definition in the lower portion and there is too much of a smiley image
Why might there be a white lined off section of the image that still has some of the true image definition showing (not completely white like collimator errors)
As the film has been put into the reader the plastic bag that covers it has been removed too quickly and caused over exposure
What might cause guitar like lines on the image
when pushing the plate into the reader it becomes stuck a little and yeh probably crinkled or something
What happens if you put 2 films in at once
One will overlap the other in the image and will just show black in the overlap and it will prevent radiation from reaching the underlying film
Why can you see on the image if you dont wash it properly
leaves the chemicals remaining in the gelatin and they go brown quickly and make you lose definition
Why might you see tree root like patterns on the image
static electricity between the film and metal feed in tray and yeh
Name the 3 types of potential exposure errors
- Overexposed
- Underexposed
- Contrast errors
What kind of exposure errors do too light and too dark images
too light = underecposure
too dark = overexposure
What effect can mAS have on the images (tube current/second)
Low mAS = whiter image due to less electrons and so less photons
High mAS = darker image due to overepxosure due to too many electrons and photons, still good contrast
What effect can changing the kV have
This will change the photon penetrating power.
Low kV = not very penetrating and so they dont really reach the film
High kV = lose ideal contrast because the high, medium and low energy photons reach the film and shows a more grey image
Why is digital better than conventional
Slight differences of kV and mAS show less problems
