Exam 1.13: Extraoral Plain Skull Radiographs

Question 1

What is the extraoral film cassette

Answer 1

Rigid container for screen/film combination

Question 2

What should the tube side of the cassette be made from

Answer 2

Bakelite, plastic

Something with a small atomic number

Question 3

What are intensifying screens made from

Answer 3

layer of flat crystals of lanthanum or gadolinium

Question 4

What size screens are there

Answer 4

8x10

10x12

Question 5

What is the purpose of the intensifying screen?

Answer 5

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

Question 6

Can you mix and match film types with screen types?

Answer 6

No, they are specifically paired

Question 7

Can you view the radiograph after the film is exposed?

Answer 7

No, you still have to develop it

Question 8

What is the purpose of a plain skull radiograph

Answer 8

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

Question 9

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

Answer 9

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

Question 10

Extraoral films should be checked for this bewteen contralateral structures

Answer 10

Symmetry

Question 11

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

Answer 11

Paranasal sinus

Question 12

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

Answer 12

soft tissue abnormalities

Question 13

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

Answer 13

Waters view (Occipitomental)

Question 14

What does waters view permit assessment of?

Answer 14

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

Question 15

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

Answer 15

Water’s view

Question 16

How do you position the patient for water’s view

Answer 16

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

Question 17

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

Answer 17

Pseudocyst

Question 18

This projection best demonstrates midline and posterior facial structures

Answer 18

Posteroanterior projection

Question 19

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

Answer 19

Posteroanterior projection

Question 20

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

Answer 20

Maxillary Sinuses

Question 21

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

Answer 21

Lamina papyracea

Question 22

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

Answer 22

Posteroanterior projection

Question 23

How do you position the patient for a posteroanterior projection

Answer 23

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

Question 24

What pathosis are illustrated by the posteroanterior projection

Answer 24

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

Question 25

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

Answer 25

Lateral projection

Question 26

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

Answer 26

Lateral projection

Question 27

What is the lateral projection essential for

Answer 27

Evaluating trauma to the sinuses

Question 28

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

Answer 28

sella turcica

Question 29

Patient placement for lateral projection

Answer 29

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

Question 30

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

Answer 30

``` Std. = 36-40 Ceph = 60 with wedge filter ```

Question 31

The lateral projection indicates

Answer 31

Sinusitis Osteopetrosis AOB

Question 32

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

Answer 32

Submentovertex (SMV)

Question 33

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

Answer 33

Jug handle fractures of the zygomatic arch

Question 34

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

Answer 34

Left and Right Sphenoid

Question 35

How do you position the patient for the SMV

Answer 35

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

Question 36

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

Answer 36

1/3

Question 37

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

Answer 37

Reverse-Towne

Question 38

What else does the Reverse Townes Projection permit evaluation of

Answer 38

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

Question 39

How do you position the patient for the Reverse Townes Projection

Answer 39

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