Radiology Third Year

1. EXTRA ORAL TECHNIQUES
PART II
By
Dr. Hassan M. Abouelkheir
.BDS, MSC, PHD

2. Types of Extra-Oral Radiographic
:Examination
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1- Mandibular oblique lateral (Ramus,
Body).
2- True Lateral (cephalometric).
3-Submento-vertex view.
4- Water’s projection (occipitomental).
5- postero-anterior projection.
6- Reverse Town’s projection.
7- Linear tomography.

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4-Occiptomental (water ’s
view):
Standard OM 0°
It shows facial skeleton
and maxillary antra and
avoids superimposition of
the dense bones of skull
base.
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Indications:
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1- Investigation of the
maxillary antra.
2- detection of middle
third fractures.
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4. Occipitomental (cont.):
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3- Coronoid process
fractures.
4- Frontal and ethmoidal
sinuses.
5- Sphenoidal sinus
investigation.
Technique:
Radiographic baseline
45° to the film (nosechin) position. Central
ray go through occiput
(0°).

5. Waters
(Sinus view)
Evaluate the maxillary sinus
MSP
FP
extraoral x-ray
unit
tip of nose 1” from
cassette
floor
CR

6. Occipitomental (water’s view):

7. Occipitomental 30 °(water’s view):
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This projection
demonstrate:
1( fracture of middle third
of face, including orbital
floor.
2( blow out fracture of
orbit..
3( fracture of zygomatic
arch.
X-ray beam
30°downword to the floor
centered through the
lower border of the orbit

8. ):Occipitomental 30 °(water’s view

9. Caldwell
(Orbit view)
Identify trauma, especially to area of orbit
MSP
FP
CR
extraoral x-ray unit
floor
tip of nose and chin
even with cassette

12. Posteroanterior (PA) Skull- 5
Identify trauma, pathology, or
developmental abnormalities
MSP
extraoral x-ray unit
FP
floor

14. Postero-anterior view (cont.)
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X-ray beam passes in a
posterior to anterior
direction through the
skull .
Uses:
• Facial growth and
development.
• Frontal & ethmoidal
sinuses.
• Orbital & nasal cavity.

15. Postero-anterior view (cont.)
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Film placement: long
axis of the cassette is
positioned vertically.
Head position: pt
faces cassette
Canthometal line is
10° above the
horizontal
Central ray ► center
of head ┴ cassette.

16. Postero-anterior view (cont.)

17. 6- Reverse Townes
Image fractures of the condylar neck
MSP
extraoral x-ray
unit
head tipped down
mouth open
FP
CR
floor

18. Reverse -Towne view (cont.):
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Used for
examination of
fracture of condylar
neck.
Postero-anterior
wall of maxillary
sinus.
Film position:
cassette is placed
vertically.

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Reverse -Towne view
(cont.):
Head position: pt
faces the cassette
with head tipped
down and mouth
open widely.
Central ray
►center of head ┴
cassette.

20. Reverse -Towne view (cont.):

24. 7- Linear Tomography
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It is a technique by
which structures are
blurred below &
above a certain
plane at which
image is sharp
(tomographic cut).
This is done by filmtube assembly
connected by pivot
and moved opposite
to each other.

25. •
.(Tomography (cont
Conventional film-based
tomography (body section
tomography) is applied
primarily to high contrast
anatomy such as TMJ and
dental implants.
The examination begins with the
x-ray tube and film
positioned on opposite sides
of the fulcrum, which is
located within the body’s
plane of interest (focal
plane). As the exposure
begins, the tube and film
move in opposite directions
simultaneously through a
mechanical linkage.

26. Blurring of image increases in
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The farther the structure lies from focal plane ,
the greater the distance between structure and
film.
The long axis of blurred structure perpendicular
to the direction of tube travel
The greater of tomographic angle or arc.

27. .(Tomography (cont
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There are 5 types of tomographic movements:
1-Linear.
2-Circular.
3- trispiral.
4- Elliptical.
5- Hypocycloidal.

28. Skull unit

29. .(Tomography (cont
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Linear tomography can be done by 2
ways:
1- the x-ray tube and film move in
opposite directions along a fixed fulcrum
2- both x-ray tube and film move along
concentric arcs rather than straight line.

30. Linear
Glenoid Fossa
Condyle
Articular eminence

31. •
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Drawbacks of linear
tomography
1-The blurring pattern is irregular
and incomplete.
2-Horizontal streaks (false
images or parasite lines) ,
represent the image of objects
outside the focal plane.
3- changing the angulations of
beam to focal plane leading to
Inconsistent magnification,
dimensional instability and non
uniform density.
panoramic Machines which uses
arc shape tomogram cause
distorted image because
magnification in the vertical plane
is independent of that in
horizontal plane.

32. •
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Linear Tomography
.((cont
Multidirectional Tomographic
motion is necessary as
Tomographic layer has width
(thickness of the cut) is inversely
proportion to the Tomographic
angle.
The greater the angle, the
thinner of the cut thickness.
Wide angle tomography
(>10º)allow visualization of fine
structures (1mm) but suffer from
decreased image contrast.
Narrow angle tomography (<10º)
→Zonography due to thick zone
of tissue (up to 25mm)

33. Linear

34. Multi-directional

35. Transcranial

36. Panoramic Film (special computer positioning(