DPT

Question 1

what does attenuation between x-ray tube and receptor alter?

Answer 1

number of photons reaching receptor

Question 2

how is latent image produced?

Answer 2

direct action of photons on emulsion/ phosphor plate

Question 3

what is a tomogram?

Answer 3

slice or section of tissue in focus

Question 4

what principal does dental panoramic use?

Answer 4

tomography

Question 5

what shape is the focal trough in DPT?

Answer 5

horseshoe shaped

Question 6

how is a DPT taken?

Answer 6

x-ray tube rotates behind patient
sensor/ cassette move in front of patient synchronised with tubehead

Question 7

how may the focal trough result in poor image quality?

Answer 7

if arch shape “non standard”

Question 8

what are in cassettes?

Answer 8

intensifying screens

Question 9

what do intensifying screens do?

Answer 9

absorb x-rays and produce light

Question 10

what are advantages of intensifying screens?

Answer 10

reduced dose

Question 11

what are disadvantages of intensifying screens?

Answer 11

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

Question 12

what is indirect action film and intensifying screen replaced by in digital?

Answer 12

phosphor plates or solid state sensor/CCD

Question 13

How is patient positioned for DPT?

Answer 13

focal trough corresponds to dental arch

Question 14

what direction does x-ray tube move?

Answer 14

behind patient from right to left

Question 15

what direction does receptor move in?

Answer 15

left to right

Question 16

what is used to ensure positioning of focal tough?

Answer 16

bite block

Question 17

what happens if finger is removed from exposure switch?

Answer 17

radiation exposure and receptor movement - cant be restarted

Question 18

what are advantages of DPT?

Answer 18

minimal discomfort
both sides
sinus walls
dose reduced compared to full mouth intraorals

Question 19

what are disadvantages of DPT?

Answer 19

lack of fine detail
superimposition
patient must be correctly positioned
16 second exposure time
magnification

Question 20

where does tongue go when taking DPT?

Answer 20

roof of mouth

Question 21

what projection is the central portion?

Answer 21

posterior anterior

Question 22

what type of incisal relationship makes focal trough alignment impossible?

Answer 22

class III

Question 23

What type of views will help to reduce the dose?

Answer 23

collimated views

Question 24

what is the selection criteria for DPT in GDP?

Answer 24

1. Grossly neglected dentition.
2. Part of periodontal bone assessment.
3. Bony lesion/ unerupted tooth of a size or position that precludes complete demonstration on intra-oral radiographs.
4. Assessment of third molars IF planning surgical intervention.
5. Part of orthodontic assessment where there is clinical need to know the state of the dentition and the presence/ absence of teeth.

Question 25

What is the selection criteria for DPT in dental hospital?

Answer 25

1. Assessment for fractures of the mandible EXCEPT anteriorly
2. Assessment of maxillary sinus pathology
3. Assessment of destructive disease of the TMJ articular surfaces.
4. Pre-implant planning – alveolar bone height and position of anatomical structures.

Question 26

where would you see air shadows?

Answer 26

• Between lips
• Oral cavity
• Nasal cavity
• Oropharynx
• Nasopharynx