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135 Dental Radiography > Extra Oral Imaging > Flashcards

Extra Oral Imaging Flashcards

1
Q

Where is the receptor placed for extra oral radiology? What is it used for? When?

A

Receptor placed outside of the mouth.

Used to view larger surface area, such as the skull or jaw.

They are generally used in conjunction with an FMS

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2
Q

Why are extra oral radiographs used in conjunction with an FMS?

A

Exposures do not show clarity of teeth and bone levels for inter-proximal decay and fine diagnostic problems. Not as defined or as sharp as an intra oral image

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3
Q

When are extra oral exposures used that are not supplemental to an FMS?

A

When swelling or injury mix receptor placement impossible

When a child cannot tolerate receptors intra-orally

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4
Q

What specific things are extra oral exposures used for?

A
  • To evaluate large areas of the school and jaw
  • growth and development
  • impacted teeth
  • to detect diseases, lesions, conditions of the jaw
  • to examine the extent of large lesions
  • to evaluate trauma
  • to evaluate the TMJ
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5
Q

Which dental professionals are extra oral radiographs most valuable to?

A

Oral surgeons, orthodontists and prosthodontist

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6
Q

What are two of the special attachments called for a panoramic unit that are used to stabilize the patient’s head parallel to the receptor at right angles to the direction of the beam of radiation?

A

Cephalostat

Craniostat

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7
Q

What are the two types of intensifying screens?

A
  • Calcium tungstate screen

- Rare earth screen

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8
Q

What color light does the calcium tungstate screen emit?

A

Blue light

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9
Q

What color light does the rare earth intensifying screen emit?

A

Greenlight

Provides less radiation to the patient, is more efficient

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10
Q

Most typical size of an extra oral receptor

A

8x10

Can use an occlusal size 4 but requires more radiation and does not cover a large area

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11
Q

What holds the intensifying screen and the film tight together?

A

Cassettes

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12
Q

Which side of the cassette his face toward the tube?

A

Plastic side toward the tube

Metal side reduces scatter radiation

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13
Q

What is a grid used for?

A

Reduces scatter which reduces fog

Has led strips so radiation scatters after it hits the skin, lead absorbs it

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14
Q

Receptor placement for the lateral jaw technique: body of the mandible

A

Receptor flat against cheek, centered over body of mandible. Also parallel with body of mandible, patient holds in position with thumb under bottom edge

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15
Q

Head position for the lateral jaw technique: body of the mandible

A

Head is tipped 15° toward the side being imaged. The chin is extended and elevated slightly

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16
Q

Beam alignment for the lateral jaw technique: body of the mandible

A

Central ray directed to a point just below the inferior border of the mandible on the side opposite the receptor. Beam is directed upward and centered on the body of the mandible. Beam must be directed perpendicular to the receptor

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17
Q

Receptor placement for the lateral jaw technique: ramus of the mandible

A

Receptor flat against patients cheek, centered over the ramus. Receptors also positioned parallel with the ramus. Patient must hold receptor in position with some under edge and palm placed against outer surface surface

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18
Q

Head position for the lateral jaw technique: ramus of the mandible

A

Head tipped approximately 15° toward side being imaged. Chin is extended and elevated slightly

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19
Q

Beam alignment for the lateral jaw technique: ramus of the mandible

A

Central ray directed to a point posterior to the third molar region on the side opposite the receptor. Beam is directed upward and centered on the ramus of the mandible. Beam must be directed perpendicular to the receptor

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20
Q

What does the posterioanterior skull view evaluate?

A

Facial growth and development, trauma, developmental abnormalities. Can also see frontal and ethmoid sinuses, Orbits and nasal cavity

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21
Q

How are the receptor, head and central ray positioned for a Posterioanterior skull view?

A

Receptor placed perpendicular to the floor, and vertically
Patient face is receptor. For head and nose touch receptor, mid sagittal plane perpendicular to the floor
Central ray aligned perpendicular to the receptor

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22
Q

What does the lateral cephalemetric skull view evaluate? What can we see?

A

Facial growth and development, trauma, developmental abnormalities

We see bones of the face and skull, shows soft tissue profile

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23
Q

What does the waters technique evaluate?

A

Maxillary sinuses. Can also see frontal and ethmoid sinuses, Orbits and nasal cavity

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24
Q

What does the submentovertex projection evaluate

A

Position of condyles, base of skull, zygomatic arch. Also can see sphenoid/ethmoid sinus and lateral wall of maxillary sinus

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25
Q

What does a reverse towne projection evaluate?

A

Fx of condyle neck and ramus

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26
Q

What does the trans cranial image of the TMJ evaluate?

A

Superior surface of condyle/articular eminence. Can also compare bilateral joint spaces

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27
Q

What does TMJ tomography evaluate?

A

The TMJ. Shows structures while blurring other structures. We move x-ray and receptor in opposite directions around a fixed rotation

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28
Q

What is the image in TMJ tomography called?

A

Tomogram.

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29
Q

What are cephalometric radiographs used for?

A

Reliable for lateral growth of the skull and face. Skull and soft tissue measurement. Skull radiographs are used for making skull measurements, must be viewed for pathology prior to tracing

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30
Q

What are the two most common radiographic views?

A

Lateral (most common)
Frontal colon indicated when asymmetry is suspected. Frontal Posterionterior ( used for further study of cranial growth patterns)

31
Q

What do cephalometric radiographs help determine?

A

Help determine because of malocclusion: can be skeletal, dental, or skeletodental

32
Q

What is anthropometry

A

The science that deals with measurements of the size, weight and proportions of the human body

33
Q

Disadvantages of panoramic exposures

A

Cannot detect height of alveolar bone and inter-proximal decay

Varying degrees of magnification, distortion and definition. As well as overlapping because it is exposed outside of the patient’s mouth

34
Q

Advantages of panoramic exposures

A

To detect pathology that cannot be seen on intra oral radiographs

Radiation dose is relatively low


35
Q

What are indications for using panoramic exposures?

A

Orthodontics: exhibit spacing and crowding of teeth, growth of both jaws and development of teeth
Surgery: impacted third molar, fractures, outline of pathologic lesions
Periodontics: exhibit condition of bone supporting the teeth
Miscellaneous: absence of teeth, impacted or unerupted Teeth and foreign bodies

36
Q

What is the image size of a panoramic exposure?

A

5 to 6 inches wide and 12 inches long

37
Q

What is the principal that the panoramic machine operates on?

A

Principle of curved surface laminography (tomography)

38
Q

What is tomography?

A

Recording of selected layers of body tissue on a radiograph

39
Q

What is seen on a panoramic image

A

Entire Dentition, surrounding alveolar bone, sinuses and TMJ

40
Q

What is the exposure time for a panoramic image? How does it compare to an FMS

A

Three minutes compared to 15 minutes for an FMS. Actual exposure time is 10 to 30 seconds

41
Q

What is the definition of fundamental of rotational panoramic radiography?

A

Technique for making radiographic projections by utilizing a narrow beam of x-rays to image a curved layer. X-ray beam is directed toward the moving cassette to record a selected plane of dental anatomy

42
Q

What is the rotational center?

A

The axis on which the tube head and cassette rotate, is the functional focus of the projection

43
Q

What does it mean if an x-ray beam is collimated?

A

 narrow opening in the tube head means less tissue is irradiated

44
Q

What is the focal trough

A

Theoretical concept, zone of sharpness.

A plane extends through the trough with objects in that plane are recorded with diagnostic sharpness. Objects are located at various distances from the plane which become less sharp as they get farther from the plane

Outside FT= blurry
Inside FT= clear

45
Q

What is the main factor that determines the width of the focal trough?

A

Distance from the function center of rotation to the object (structure to be radiographed)

46
Q

What is a real image?

A

When a structure is between the rotation center and receptor

47
Q

What is a double image?

A

Structure behind the rotation center, penetrated twice by the beam

48
Q

What is a Ghost image

A

Outside of the focal plane, close to x-ray source, blurred/magnified, On opposite side of the image and higher up

49
Q

What is the Frankfort plane?

A

Horizontal plane between porion with orbitale

50
Q

What is the porion?

A

Mid portion of the upper edge of the external auditory meatus

51
Q

What is the orbitale?

A

Lowest point on the contour of the bony orbit

52
Q

Where most of the Frankfurt plane be?

A

Parallel to the lines on the head stabilizer

53
Q

Where should the sagittal plane be?

A

Perpendicular to the floor; position at midline or mid sagittal plane

54
Q

Where should the teeth be positioned?

A

In the focal trough

55
Q

Where should the tongue be during a panoramic exposure

A

On the roof of the patient’s mouth. Then ask them to swallow. Closes palatoglossal air space

56
Q

Common errors in panoramic imaging

A
  • Artifacts
  • ghost image
  • lead apron
57
Q

Positioning errors in panoramic imaging

A
  • Lips not closed on bite block cause a dark shadow that it scares front teeth
  • tongue not in contact with pallet causes a dark shadow that it scares the apices of the maxillary teeth
  • Frankfurt plane up or down
  • teeth Anterior or Posterior to focal trough
  • mid sagittal plane not perpendicular to the floor
  • Slumped spine
58
Q

Why do we need to use descriptive term analogy when documenting interpretations?

A

We need to communicate using a common language: patient may be referred to a specialist. Document lesions in patient record

59
Q

What will show up as radiolucent on a radiograph?

A

Air spaces, soft tissue, pulp, periodontal ligament, carries and loss of bone

Ex. Soft tissue cyst, abscess, granuloma, tumor, neoplasms, carcinoma, sarcomas, lymphoma

60
Q

What does it mean when a lesion has a unilocular corticated border?

A

Is a space with a well defined radiopaque border indicative of a benign, slow growing process

61
Q

What does it mean when a lesion has a unilocular non-corticated border?

A

Is a space with fuzzy, non-defined water. Benign or malignant

62
Q

What does it mean when a lesion is multilocular?

A

Resembles soap bubbles, usually well-defined borders. Large and expansive, displaces lingual and buccal plates of bone. Benign with aggressive growth

63
Q

What will show up as radiopaque on a radiograph?

A

Dense tissue or materials.

Ex. Hard tissue osteitis, sclerotic bone, odontoma, hard tissue tumors, fibroma, sarcoma‘s, carcinoma, calcified glands and nodes, foreign bodies, ossification etc.

64
Q

What describes a focal opacity?

A

Well defined in the localized

65
Q

What describes a target Lesion?

A

Well defined, localized, but surrounded by a radiolucent halo

66
Q

What describes multifocal confluent?

A

Multiple radiopacities that overlap or flow together

67
Q

What is described as irregular?

A

Poorly defined pattern

68
Q

What is described as ground glass?

A

Granular or pebbled

69
Q

What is described as mixed lucent opaque

A

Mixed radiopaque and radiolucent

70
Q

What is described as soft tissue opacity?

A

Well defined, located in soft tissue

71
Q

What does inter-radicular mean

A

Between roots of adjacent teeth

72
Q

What is an edentous zone

A

Location without teeth

73
Q

What does pericoronal mean?

A

Around the crown of an impacted tooth

135 Dental Radiography (23 decks)

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