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