Radiology - Panoramic

Question 1

What are the uses of panoramic radiographs? (5)

Answer 1

tooth development - ortho

jaw development and abnormalities

oral disease

pathology

trauma

Question 2

what technique is used in panoramic radiographs?

Answer 2

linear tomography

Question 3

describe how linear tomography work?

Answer 3

both the image receptor and x-ray source are continuously moving from left to right

teeth are the only things staying in the same place = the focal trough/image layer

Question 4

what structrues should be present in the focal trough/image layer (layer in focus)?

Answer 4

all the teeth

structures above and below the teeth

structures superficial and deep to the teeth

Question 5

what does the distance from the teeth to the rotation centres influence?

Answer 5

width of the image layer in focus

horizontal distortion

ghost images

Question 6

describe the speed of the x-ray beam for posterior teeth.

Answer 6

Posterior teeth are further away from their rotation centres so the x-ray beam has to be faster passing through the teeth.

• movement of the image receptor also has to be fast to match this and prevent distortion

Question 7

describe the speed of the x-ray beam for anterior teeth.

Answer 7

Since the rotation centre is closer to anterior teeth the passage of the X-ray beam is slower.

• movement of the image receptor also has to be slow to match this and prevent distortion

Question 8

what is the width of the image layer dependant on?

Answer 8

the width of the x-ray beam

distance to the rotation centre

Question 9

what distance from the rotation centre creates a narrow image?

Answer 9

closer (anterior teeth)

Question 10

what distance from the rotation centre creates a wider image?

Answer 10

further away (posterior teeth)

Question 11

what position must the patient be in for a panoramic radiograph?

Answer 11

frankfort plane horizontal to the floor

Question 12

define the frankfort plane.

Answer 12

the lower border of the orbit / orbital rim

to

the upper border of the external auditory meatus

Question 13

What must the patient remove before taking a panoramic radiograph?

Answer 13

glasses

metal objects - necklaces, piercings

dentures
other mouth appliances

Question 14

what must you check before taking a panoramic radiograph? (3)

Answer 14

no metal objects etc

frankfort plane is horizontal

red vertical light is shining on the upper canine

Question 15

What are the limitations of panoramics? (5)

Answer 15

malocclusion - cant bite on to the peg

long exposure time - problem for nervous patients, children, special needs

big shoulders, obese, spinal issues

incorrect width of focus

horizontal distortion

Question 16

what signs on a panoramic radiograph indicate movement?

Answer 16

wavy lower border of the mandible

abnormally large teeth - have to consider the fact they could have megadonts

Question 17

what happens to the image if the Patients canine is behind the canine guide line?

Answer 17

The image is magnified horizontally.

Question 18

what happens if the Patients canine is in front of the canine guide line?

Answer 18

The image is reduced in width horizontally

Question 19

what structures are commonly subject to ghost images? (4)

Answer 19

Earrings

Metal restorations

Anatomical features - ramus and angle of the mandible (opposite sides)

Soft tissue calcifications - i.e. lymph nodes and salivary glands.

Question 20

where are ghost images usually found on a radiograph? (3)

Answer 20

higher up

horizontally magnified

further forward