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D2: 621 Radiology > Exam 1.13: Extraoral Plain Skull Radiographs > Flashcards

Exam 1.13: Extraoral Plain Skull Radiographs Flashcards

1
Q

What is the extraoral film cassette

A

Rigid container for screen/film combination

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2
Q

What should the tube side of the cassette be made from

A

Bakelite, plastic

Something with a small atomic number

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3
Q

What are intensifying screens made from

A

layer of flat crystals of lanthanum or gadolinium

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4
Q

What size screens are there

A

8x10

10x12

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5
Q

What is the purpose of the intensifying screen?

A

Radiation hits the crystals and emits a flash of visible green light that helps expose the film

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6
Q

Can you mix and match film types with screen types?

A

No, they are specifically paired

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7
Q

Can you view the radiograph after the film is exposed?

A

No, you still have to develop it

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8
Q

What is the purpose of a plain skull radiograph

A

When pathoses are discovered on the pan, you need at least one more film perpendicular to the original to assist in the spatial localization of the pathosis

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9
Q

What anatomical land mark is important for extraoral plain skull projections?

A

Canthomeatal line which runs from the external auditory meatus to the outer cantus of the eye

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10
Q

Extraoral films should be checked for this bewteen contralateral structures

A

Symmetry

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11
Q

All major structures of the midface border at leasts one of these…

A

Paranasal sinus

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12
Q

Swelling, sings of penetrating injury, intraorbital air and soft tissue calcifications and masses are all…

A

soft tissue abnormalities

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13
Q

This view demonstrates medial and lateral walls of the maxillary sinuses and anterior facial structures including the medial wall of the orbit free of superimposition of the petrous ridges of the temporal bone

A

Waters view (Occipitomental)

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14
Q

What does waters view permit assessment of?

A

Zygomatic buttresses, orbital rims, nasal bones, anterior lamina, papyracea, ethmoid air cells, frontal sinuses

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15
Q

Only this view projects the anterior and posterior ethmoid air cells seperately

A

Water’s view

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16
Q

How do you position the patient for water’s view

A

Sagittal plane perpendicular to film
Chin raised high so that the canthomeatal line is 37 degrees above horizontal
Central ray should be perpendicular to the film at the level of the maxillary sinus
Source-film distance is 36-40

17
Q

What abnormality of the maxillary sinus can be projected by a water’s view

A

Pseudocyst

18
Q

This projection best demonstrates midline and posterior facial structures

A

Posteroanterior projection

19
Q

What is the projection of choice for demonstrating orbits, frontal and ethmoid sinuses and nasal fossa

A

Posteroanterior projection

20
Q

What is not well visualized due to the superimposition of the petrous ridges in a posteroanterior projection?

A

Maxillary Sinuses

21
Q

What is well visualized in a posteroanterior projection thanks to seperation of the ethmoid air cells from the orbits

A

Lamina papyracea

22
Q

What radiograph is good for detecting mediolateral changes in the skull including asymmetry

A

Posteroanterior projection

23
Q

How do you position the patient for a posteroanterior projection

A

Head centered in front of the cassette
Canthommeatal line parallel to the floor so the occlusal plane is horizontally oriented
Central ray is directed perpendicular to the plane of the film
Source to film distance of 36-40

24
Q

What pathosis are illustrated by the posteroanterior projection

A 
Cysts in ethmoid airspaces
Pagets ds CX
Cherubism
Fibrous dysplasia
Leiomyosarcoma
Surgery results
Glass eyes
25
Q

This projection is the best for evaluating the anterior and posterior walls of the maxillary, frontal, ethmoid, and sphenoid sinuses and the pterygomaxillary buttress

A

Lateral projection

26
Q

What is the best projection for evaluating an air fluid level in the maxillary sinuses

A

Lateral projection

27
Q

What is the lateral projection essential for

A

Evaluating trauma to the sinuses

28
Q

The lateral projection illustrates the relationship of the sphenoid sinus to this

A

sella turcica

29
Q

Patient placement for lateral projection

A

Left side of face adjacent to the cassette and midsagittal plane parallel with the film
central ray is oriented toward the external auditory meatus and perpendicular to the midsagittal plane

30
Q

For the lateral projection, what is the difference in source to film distances for a standard skull vs. a Ceph?

A 
Std. = 36-40
Ceph = 60 with wedge filter
31
Q

The lateral projection indicates

A

Sinusitis
Osteopetrosis
AOB

32
Q

This projection demonstrates the base of the skull, the position and orientation of the condyles, the cur of the mandible, the lateral wall of the maxillary sinuses, and the pterygoid plates

A

Submentovertex (SMV)

33
Q

What type of fractures does the SMV do a good job of demonstrating?

A

Jug handle fractures of the zygomatic arch

34
Q

The SMV is the only projection that shows these two sinuses seperately

A

Left and Right Sphenoid

35
Q

How do you position the patient for the SMV

A

Head extended backwards with vertex on center of cassette

Midsagittal plane must remain perpendicular to the floor

The canthomeatal line should extend 10 degrees past vertical

CRay from below the mandible up toward the vertex of the skull; passing 2 cm in front of imaginary line between the two condyles

36
Q

By what factor do you reduce the exposure time if you are specifically viewing the zygomatic arches

A

1/3

37
Q

What is the most important plain film for assessing subcondylar fractures because it accurately demonstrates the angulation and/or displacement that occurs as a result of them

A

Reverse-Towne

38
Q

What else does the Reverse Townes Projection permit evaluation of

A

Petrous Ridges and mastoid air cells and posterolateral wall of the maxillary antrum

39
Q

How do you position the patient for the Reverse Townes Projection

A

Head in front of cassette with Canthomeatal line oriented downward 25-30 degrees.

Patients mouth fully open

Rays are directed toward the film in the sagittal plane through the occipital bone

Beam is collimated to prevent exposure and fog

D2: 621 Radiology (16 decks)

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