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Oral Radiology > Panoramic Imaging Principles > Flashcards

Panoramic Imaging Principles Flashcards

1
Q

what are the indications for panoramics

A
  • overall evaluation of dentition
  • intraosseous pathology
  • gross evaluations of the TMJ
  • evaluation of position of impacted teeth - 3rd moalrs
  • evaluation of dental development and eruption
  • dentomaxillofacial trauma
  • developmental disturbances of the maxillofacial skeleton
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2
Q

what are advantages of panoramic over FMS

A
  • relatively low radiation dose
  • broad coverage of facial bones and teeth
  • easier technique
  • can be used in patients with trismus or in patients who cannot tolerate intraoral radiographs
  • quick and convenient radiographic technique
  • useful visual aid in patient education
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3
Q

what are disadvantages of panoramic over FMS

A
  • lower resolution images (no possible to detect small carious lesions or early periapical disese)
  • overlap in the premolar area
  • magnification across image is unequal, making linear measurements unreliable
  • image is superimposition of real, double and ghost images
  • requires accurate patient positioning to avoid positioning errors and artifacts
  • difficult to image both jaws when patient has severe maxillomandibular discrepancy
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4
Q

how does pano work

A
  • direction of receptor past collimator
  • direction of xray source around patient
  • direction of receptor and collimator around patient
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5
Q

what is the continuous movement of pano source

A
  • starts on the R side
  • continues behind head
  • ends up on the L side
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6
Q

when the source is on the right side, the ____ side of the mandible is being imaged

A

left

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7
Q

the sensor is never______

A

in the back of the patient

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8
Q

the x ray tubehead is never ______

A

in front of the patient

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9
Q

what is the focal trough

A

a three dimensional curved zone in which structures are reasonably well defined
- where dental arches must be positioned to achieve sharpest images

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10
Q

describe objects outside the focal trough

A

blurred, magnified or reduced in size and are sometimes distorted to the extend of not being recognizable

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11
Q

what structures are the clearest in the focal trough

A

structures positioned in the center of the focal trough

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12
Q

what is the issue with the center of rotation and what is the solution

A
  • not just one
  • we cannot follow the shape of the mandible
  • solution: multiple and constantly moving centers of rotation
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13
Q

what is the pano unit that we use downstairs

A

orthophos XG sirona

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14
Q

objects closer to the receptor will be:

A

narrowed

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15
Q

objects closer to the source will be:

A

widened

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16
Q

buccal objects will be projected:

A

lower

17
Q

lingual objects are projected:

A

higher

18
Q

what is the beam angulation and why

A

about -4 degrees to avoid projection of the occipital bone

19
Q

structures closer to the source are projected:

A

higher up on the image

20
Q

distance between the _____ and the _____can be misrepresented on a pano

A

root apex and mandibular canal

21
Q

horizontal magnification is determined by:

A

the position of the object within the focal trough

22
Q

lingual to the focal trough ->

A

closer to the source -> appears wider

23
Q

buccal to the focal trough ->

A

appears narrow

24
Q

the magnitude of the horizontal distortion depends on the:

A

distance of the object from the center of the focal trough

25
Q

describe horizontal magnification in the anterior region

A

increases as the object moves away from the center of the focal trough

26
Q

is the degree of magnification higher in the posterior or anterior

A

anterior

26
Q

horizontal measurements made on pano images are:

A

unreliable

27
Q

what are real images

A

every anatomical structure positioned between the center of rotation and the receptor

28
Q

what are ghost images created by

A

objects located between the x ray source and the center of rotation

29
Q

where do ghost images appear

A

on the opposite side at a higher level, blurred and magnifiedw

30
Q

what are the anatomical structures that cast a ghost image

A
  • inferior border of the mandible
  • angle
  • ramus
  • hyoid
  • cervical spine
  • jewelry
  • palate
31
Q

what are the characterisitcs of the ghost shadows

A
  • appears on the appposite side
  • positioned higher than real structure
  • more blurred than the real structure
  • vertical components is highly magnified
32
Q

what are double images

A

objects that lie posterior to the center of rotation and that are intercepted twice by the x ray beam

33
Q

what are the anatomical structures that are double images

A
  • hyoid bone
  • epiglottis
  • cervical spine
  • cast images on the right and left side of the image
34
Q

all double images are _____

A

real images

35
Q

what is the positioning of the patient in panos

A
  • remove jewlery, glasses, and dentures
  • place lead apron
  • bite in biteblock groove
  • stand patient upright
  • align the center laser line
  • align the frankfurt horizontal plane
  • close side guides
  • have the pt close their lips, swallow and keep tongue on the palate and hold still
  • expose the radiograph
36
Q
A

Oral Radiology (26 decks)

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