DPT Flashcards
what does attenuation between x-ray tube and receptor alter?
number of photons reaching receptor
how is latent image produced?
direct action of photons on emulsion/ phosphor plate
what is a tomogram?
slice or section of tissue in focus
what principal does dental panoramic use?
tomography
what shape is the focal trough in DPT?
horseshoe shaped
how is a DPT taken?
x-ray tube rotates behind patient
sensor/ cassette move in front of patient synchronised with tubehead
how may the focal trough result in poor image quality?
if arch shape “non standard”
what are in cassettes?
intensifying screens
what do intensifying screens do?
absorb x-rays and produce light
what are advantages of intensifying screens?
reduced dose
what are disadvantages of intensifying screens?
light is emitted in all directions
light affects larger area of film than a single photon
image qaulity is not as good as direct action film
what is indirect action film and intensifying screen replaced by in digital?
phosphor plates or solid state sensor/CCD
How is patient positioned for DPT?
focal trough corresponds to dental arch
what direction does x-ray tube move?
behind patient from right to left
what direction does receptor move in?
left to right
what is used to ensure positioning of focal tough?
bite block
what happens if finger is removed from exposure switch?
radiation exposure and receptor movement - cant be restarted
what are advantages of DPT?
minimal discomfort
both sides
sinus walls
dose reduced compared to full mouth intraorals
what are disadvantages of DPT?
lack of fine detail
superimposition
patient must be correctly positioned
16 second exposure time
magnification
where does tongue go when taking DPT?
roof of mouth
what projection is the central portion?
posterior anterior
what type of incisal relationship makes focal trough alignment impossible?
class III
What type of views will help to reduce the dose?
collimated views
what is the selection criteria for DPT in GDP?
- Grossly neglected dentition.
- Part of periodontal bone assessment.
- Bony lesion/ unerupted tooth of a size or position that precludes complete demonstration on intra-oral radiographs.
- Assessment of third molars IF planning surgical intervention.
- Part of orthodontic assessment where there is clinical need to know the state of the dentition and the presence/ absence of teeth.
