Intro to dental radiology Flashcards
What are the 3 basic principles of radiation protection?
- Justification
- Optimisation
- Dose limitation
Who does the basic principle of radiation protection ‘dose limitation’ apply to?
- For radiation workers and members of the public, NOT patients
What does the ‘justification’ principle of radiation protection mean?
- Deciding for each time we think we want a radiograph that it is justified - is it going to be of benefit to the patient
What does the ‘optimisation’ principle of radiation protection mean?
- ALARA (as low as reasonably achievable) - the does of radiation that we give to the patient when we give a diagnostic radiograph should be as low as reasonably achievable
What does ALARA mean?
As low as reasonably achievable
ALARA was changed to ALARP. What does ALARP mean?
As low as reasonably practicable
What is the source of an x-ray?
The x-ray machine
What does an x-ray machine do?
Produces x-rays
What objects are we using x-ray images to analyse?
Teeth and jaws
What are the 3 different types of image receptor?
- Digital receptors
- x-ray film packets (intra oral)
- Screen-film combinations (extra-oral) (hardly used now)
What type of image receptor is used the majority of the time now?
Digital receptors
What are the 2 different types of digital image receptor?
- Direct and indirect
What kind of x-ray are direct digital receptors used for?
- Panoramics
How do direct digital image receptors work?
- The interact with x-ray and image comes up almost instantly
What kind of radiographs are indirect digital image receptors used for?
- Intra-orals
How do indirect digital image receptors work?
After the sensor has been exposed to x-rays it doesn’t look any different - has to go through a machine in order to produce the image - this is called processing
- Because we can’t see it immediately the image is describes as a latent image and has to be converted into a permanent visible image (done using a computer or chemicals)
What does ‘processing’ mean?
Conversion of latent image to permanent visible image:
- Digital
- Chemical
You need to have a very high voltage to produce x-rays which means you have to convert the domestic electricity supply to the high voltage. What are the values of the domestic and high voltage supply?
- Domestic = 240 volts
- High voltage = 60-70 thousand volts for a small intra-oral
- Panoramic machines have a higher kV
What is the direction of travel of electromagnetic radiation?
- Straight, diverging beam
What is the inverse square law?
A law which explains the intensity of a unit point related to the distance from the source
X-rays have photographic properties. What does this mean?
This enables images to be created
X-rays interaction with matter is crucial to be able to get an image. What ways are x-rays able to interact with matter? (3 points)
- No effect
- Complete absorption
- Absorption and scatter
Give an example of a materials where x-rays will just pass through with no interaction at all?
- Air
How do x-rays interact with materials like amalgam and gold?
- They will be completely absorbed by these materials. This absorption will result in a white image
Why can having materials like amalgam etc be harmful when talking x-rays?
- The absorption is useful as it gives us an image of the mouth but it is also transferring energy to the patient which is giving them a dose which is adding to the potential for harm
One type of x-rays interaction with matter is absorption and scatter. Why can this be harmful to the patient?
- You only get partial absorption of energy in the x-ray beam but the individual component of the beam also has its direction changed (also going to add dose - this has the potential to exit the patient and if the patient has someone near to them giving a dose to that person - that’s why people in the vicinity of x-ray machines have to exercise some care)
What is a radiographic image?
- It is a pictorial representation of a part of the body
A radiographic image is a pattern of attenuation of the x-ray beam after it has passed through matter. What does this mean?
- Attenuation = the combination of absorption and scatter events and how it has reduced the intensity of the x-ray beam
- You see shades going from almost black to white
- These shades are what happens to the x-ray beam as it has passed through the tissues going from complete absorption where we have amalgam fillings to where we have no absorption in the black bits (describe this as pattern of attenuation)
What are the types of intra-oral radiographs we use? (3)
- Bitewings
- Periapicals
- Occlusals
Where does the image receptor go for an intra oral radiograph?
- Inside the patients mouth
What are the different types of extra-oral radiographs we use? (2)
- Panoramic
- Cephalometric (view of the facial skeleton)
Where is the image receptor put for an extra-oral radiograph?
- Stays outside the patients mouth
- Therefore the image is going to be bigger
What is a cone beam CT radiograph?
- A form of cross-sectional 3D imaging
What do cone beam CT radiographs allow us to look at?
- Very thin slices of the patient from different views
What does the CT in cone beam CT stand for?
- Computer Tomography
What is one of the most common reasons why we would use a bitewing radiograph?
- To look for caries
- But we also see the interdental bone so also need to think about periodontal disease affecting the bone
What teeth do we see in a bitewing radiograph?
- Side teeth (molars and premolars)
What are our requirements for an optimal bitewing radiograph? (2)
- Symmetry of upper and lower teeth
- Minimal overlap of adjacent teeth
Can you see the interdental bone on a bitewing radiograph?
Yes
What are the conditions for an ideal bitewing radiograph? (6)
- Upper and lower crowns of one side
Want to pick up:
- Mesial first premolar contact to most dital contact point or surface of the last tooth
- None, or minimal ovrlap of teeth
Want to see these:
- Enamel-dentine junction
- Coronal pulp morphology
- Interdental bone
What are the key points when taking bitewings? (4)
- Show upper and lower cheek teeth of one side
- From distal of canine posteriorly, to include all contact points
- Take R and L
- One per side unless all premolars and molars present (in which case would need 2 in order to see)
What pathologies/things can we see or look for in bitewings? (5)
- Interproximal caries
- Cervical caries
- Occlusal, buccal & lingual caires
- Restorations: led g es, defects
- Interdental bone changes
What part of the tooth does a periapical radiograph show?
- The full length of at least 1 tooth
What does ‘periapical’ mean?
PEri = around
Apical = the apex or tip of the tooth
What pathologies/things can you identify from a periapical radiograph? (5)
- Crown - caries, trauma, other non-carious tooth surface loss
- Changes related to restorations
- Pulpal pathology
- Root
- Supporting bone
You can take an oblique occlusal radiograph. What is this similar to?
- Similar to a large periapical
What can you see when you take a true (cross-sectional) occlusal radiograph?
- Plan view of a section of the mandible or floor of the mouth
Where is the film packet put in an occlusal radiograph?
- In the occlusal plane
What can DPR mean?
- Dental panoramic radiograph
What part of the dentition does a panoramic radiograph show you?
- A full view of the dentition
What sort of image does a panoramic radiograph show you?
- An mage of a layer, not full thickness of all structures between x-ray source and image receptor
What do Cephalometric radiographs give you a view of?
- View of the facial bones to enable measurement of dental and skeletal relationships
What kind of view does a cephalometric radiograph give you?
- Usually lateral view (true lateral)
Do cephalometric radiographs include a soft tissue profile?
- Yes
