Panoramic

Question 1

What is the focal trough

Answer 1

The focal trough is the image layer that contains the structures of interest. Anything in the trough will be clear, anything not will be blurred

Question 2

What is the direction of the beam

Answer 2

lingual to buccal

Question 3

Where is the rotation centre

Answer 3

Continually changes
o Posterior teeth are further from the rotation centre (faster beam passage)
o Anterior teeth are closer to the rotation centre (slower beam passage)

Question 4

How does the distance from the rotation centure impact the teeth

Answer 4

o Width of focal trough
o Horizontal distortion if px in incorrect position
o Ghost images

Question 5

What is the vertical angle

Answer 5

-8

Question 6

What plane is of significance

Answer 6

o Frankfurt plane is horizontal to the floor

Question 7

What are ghost images

Answer 7

Ghost images are created by the tomographic movement and cast by structures on the opposite side of a long way from the focal trough

Question 8

How do ghost images occur

Answer 8

• Due to the 8 upward angulation of the beam this means that the ghost images often appear at a higher level than the structures that have caused them
• The more important ghost shadows include cervical vertebrae, body, angle and ramus of the contralateral side of the mandible and the palate
• They tend to be magnified horizontally and appear more anterior

Question 9

What does patient malposition cause

Answer 9

can be represented mainly as distortion in the horizontal plane so that the teeth are too wide or narrow rather than foreshortened or elongated e.g if patient rotated to the left and the left teeth are nearer the film and will be narrower while the teeth on the right will be further away from the film and wider

Question 10

What are the applications of panoramic

Answer 10

o development of the dentition
o developmental and acquired anomalies
o caries, pulpal and periodontal disease
o pathological jaw lesions
o trauma
o surgery – evaluation and review

Question 11

What are px preparation errors

Answer 11

Failure to remove jewelry
* earrings
* necklaces
* piercings
Failure to remove dentures
Failure to remove orthodontic appliances
Failure to remove spectacles
Inappropriate use of lead apron

Question 12

What are patient positioning errors

Answer 12

• failure to ensure that the spine is straight – ghosting error
• failure to ensure the incisors are biting edge to edge on the bite peg – anteroposterior errors
• failure to use the light beam marker to ensure the mid saggital plane is vertical and the head is not rotated (horizontal error)
• failure to use the light beam marker to ensure the Frankfort plane is horizontal (vertical error)
• failure to instruct the patient to press the tongue against the roof of their mouth – air shadow error
• failure to instruct px to remain still throughout exposure
• if px is closer to x-ray source (further back in machine or canine behind canine guidance line) then the image receptor will be too fast and the image magnified horizontally
• if the patient is further away from the x-ray source then the image receptor will be too slow and the image of the teeth will be reduced in width horizontally

Question 13

What are equipment positioning errors

Answer 13

• failure to set height adjustment correctly
• failure to select correct exposure settings
• failure to use the cassette correctly