Radiographic Techniques Flashcards
What are the three basic components of radiographs?
X-ray source
Object
Receptor
What is key to the quality of an image?
The relationship of X-ray source, object and receptor to one another
What are three types of intra-oral radiograph?
periapical
bitewing ( horizontal and vertical)]
occlusal (maxilla and mandible)
When taking an intra-oral radiograph, where would the receptor be placed?
Inside the mouth
When taking an extra-oral radiograph, where would the receptor be placed?
Alongside the patient
What are five types of extra-oral radiographs?
dental panoramic tomogram
lateral cephalogram
postero-anterior mandible
lateral oblique mandible
Occipital-mental views of facial bones
On a peri-apical radiograph, what should be visible?
The crown to the apices of the root, and inter-proximal spaces
What are the limitations of a horizontal bitewing?
You are not able to visualise the roots
What radiograph would you consider taking if you wanted to assess bone levels of posterior teeth?
Bitewing, either horizontal or vertical
What type of extra-oral radiograph is described:
The x-ray tube rotates round the patients head with a constant long exposure of 14 seconds, forming an image of the patient’s teeth and supporting structures
DPT
What type of extra-oral radiograph is described:
A standardised and reproducible form of skull radiography, used extensively in orthodontics to asses the relationships of the teeth to the jaws and the mandible to the rest of facial skeleton
Lateral cephalogram
What type of extra-oral radiograph is described:
Shows fractures of the mandible and is used in conjunction with a DPT. it requires two views taken at right angles to one another to show full extent of fracture.
Posterior-anterior mandible
It is common for there to be multiple fractures in the mandible. True or false?
True
What type of extra-oral radiograph is described:
Most commonly carried out in a dental hospital in children that cannot tolerate bitewings. Also carried out on adults for, mandibular fractures if a DPT is not available.
Lateral oblique mandible
Q
What type of extra-oral radiograph is described:
Most commonly carried out in the first instance when patient reports with facial trauma. Shows fractures of the orbit, maxilla and zygomatic arches. Two views are taken, the first angle at 10 degrees and the second angle at 30 degrees.
Occipito-mental views of facial bone
Q
When taking an occipital mental view of the facial bones, why is it beneficial to take the films erect?
As this can help demonstrates fluid levels in antra
Why are intra-oral radiographs in more detail that extra-oral?
Because the object is closer to the receptor
What selection criteria helps decide the most appropriate form of imaging required when deciding what radiograph to take?
FGDP selection criteria for dental radiography
What are the two main types of technique used for intra-oral radiographs?
paralleling technique
bisected angel technique
What is the standardised intra-oral technique?
Paralleling technique
When would you opt for the bisected angle technique over the paralleling technique?
When a patient cannot tolerate a holder in their mouth
What is the main issue surrounding bisected angle technique?
Exposure of patients fingers to radiation as they are required to hold film in mouth
What is the downside of the paralleling technique?
Holders are bulky and may not be tolerated by patient.
What part of the mouth are blue holders used to visualise?
Anterior teeth
What part of the mouth are yellow holders used to visualise?
Posterior teeth
What colour of holder is used for bitewings?
Red holder
What colour of holder is used for endodontic procedures?
Green holder
What are the three components of holders?
Bite-block
Indicator arm/rod
Aiming ring
What is the function of a bite-block?
Retains the receptor
What is the function of the indicator arm/rod?
Fits into the bite-block
What is the function of the aiming ring?
Slides onto the arm to establish alignment of collimator with receptor, guiding direction of the x-ray beam
What is a receptor?
The object an image is taken on
what type of receptors are used in dundee dental hospital?
Phosphor plates
What reduces the variables in geometry?
Use of a holder
What are examples of variables in geometry?
Receptor-tooth relationship
X-ray tube position
How should the vertical plane of the film be positioned?
So that it is parallel to the long axis of the tooth
How should the horizontal plane of the film be positioned?
Parallel to the central arch under examination
If the film isn’t parallel with the tooth vertically, what may happen?
Distortion of the image (teeth elongated and apices missing)
If horizontal positioning of the film is incorrect what may happen?
Teeth appear overlapped, obscuring pathology
What angle should the x-ray beam be to the tooth/receptor?
90 degrees ( right angle )
If the angle of the x-ray beam is up too much, how will the image be distorted?
Elongation of image
If the angle of the x-ray beam is down too much, how will the image be distorted?
Fore-shortening of image
What is the rectangular attachment at the end of the x-ray tube known as?
Collimater
what will help achieve the most diagnostic, reproducible image?
Having the 4 corners of the collimator fitting nicely into the aiming ring
What two factors affect image size?
X-ray source to receptor distance
Object to receptor distance
Explain how the object comes to appear larger on the receptor
X-ray beam spreads out in all directions from the source and it continues to spread as it passes through the object, thus making it appear larger.
What action should be taken in regards to the x-ray source in order to get a more accurate depiction of the image?
X-ray source should be positioned further away from the object (beam diverges less)
What should the distance between source and film be?
Long
What should distance between tooth and film be?
Short
What is ‘cone cutting’ a result of?
Vertical angulation, when corners of the collimator have not been touching the guiding ring.
What are the four main barriers to good positioning?
-mouth size
-gag reflex
-film size
-digital sensor size and shape
What are the 4 most common sizes of film/ PSP receptors?
0, 1, 2, 4
What should the film size be for:
Periapical radiograph of anterior adult teeth
0 or 1
What should the film size be for:
Periapical radiograph of anterior adult teeth using bisected angel technique
2
What should the film size be for:
Periapical radiograph of posterior adult teeth
2
What should the film size be for:
Bitewing radiograph of adult teeth
2
What should the film size be for:
Periapical radiograph of anterior children’s teeth
0
What should the film size be for:
Periapical radiograph of posterior children’s teeth (deciduous and permanent)
Deciduous = 0
Permanent = 2
What should the film size be for:
Bitewing radiograph of children over 10
2
What should the film size be for:
Bitewing radiograph of children under 10
0 or 1
what is the “controlled area”?
The area in the immediate vicinity around the x-ray source
What are the key four reasons to take bitewing radiographs?
To detect caries
To monitor caries progression
To assess periodontal status
To assess existing restorations
What happens in a caries risk assessment?
You perform images at regular intervals
What happens in a caries risk assessment?
You perform images at regular intervals
What are the advantages of horizontal bitewing over vertical?
Usually only two images taken whereas verticals require 4 images to be taken
What is the advantage of vertical bitewings?
They demonstrate more of the roots
In a horizontal bitewing, where should the centre of the bite block be placed so to cover the whole region of interest?
On the centre of the 6
When would you pick a vertical bitewing over a horizontal bitewing?
When you need to see more of the root and supporting bone
What are the positioning requirements for bitewings?
Film and object parallel
Film close to object
X-ray beam perpendicular to object and film
How do we achieve good positioning?
By always using a holder
what could be used as an alternative to film holder if patient cannot tolerate it?
Paper tab
What does use of a guiding ring ensure?
That the x-ray beam is certain to hit the centre of the receptor
When may horizontal overlap of teeth be difficult to avoid?
If there is crowding or tilting of teeth
When would horizontal overlap of teeth be deemed acceptable?
If less than half of enamel is superimposed
What are the two problems associated with vertical angulation of x-ray beam to receptor?
Upper bone levels will be projected off the receptor
Resultant distortion of the teeth has caused separation of the cusps
On a bitewing, where does the ‘dot’ on the receptor go?
Always to the palate
If a child refuses to cooperate with bitewings what is the alternative?
Lateral oblique mandible images
what can reduce the dose of radiation to patients by up to 50%?
Use of rectangular collimation
Why is legislation for radiology necessary?
Helps to minimise risks from radiation exposure
