1-extraoral techniques.pdf
TRANSCRIPT
DR.MOHAMMED SHAMIAH
M . S . C . O F O R A L & M A X I L L O F A C I A L S U R G E R Y
ORAL & MAXILLOFACIAL RADIOLOGY
Extra-oral Techniques
INTRO.
• Extra-oral radiograph are used alone or in
conjunction with intra- oral film because they are not
defined or sharp as intra- oral radiograph.
• Extra-oral radiography, both the X-ray source and the
image receptor are placed outside the patient’s
mouth and the X-ray beam directed toward it .
• The main anatomic landmarks used in patient
position is the cantho-mental line and the Frankfort
line.
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• The canthomeatal line is the radiological
base line and joins the central point of external auditory meatus with the outer canthus of the eye. (10 degree with Frankfort line).
• the Frankfort line which joins the superior border of the external auditory meatus with the most inferior portion of the infraorbital rim .
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• The first step on obtaining a radiograph is
the selection of the appropriate projection for the proper diagnosis.
• The proper exposure parameter depend on the patients size, anatomy, head,
orientation, image receptor speed, target-film distance and whether or not grids are used.
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THE GRID
• A grid is a device used to decrease film fog
and increase the contrast of the radiographic image.
• It does this by reducing the amount of scatter radiation that reaches an extra-oral film
during exposure.
• Scatter radiation causes film fog and reduces film contrast and resolution.
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A GRID DECREASES THE AMOUNT OF SCATTER
RADIATION THAT REACHES THE EXTRAORAL FILM.
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ORAL -INDICATION OF EXTRARADIOGRAPHY:
1- To evaluate and examine large area of the skull and jaws for pathological condition .
2- To evaluate the status of impacted teeth, trauma, TMJ, maxillary sinus and salivary glands .
3- To evaluate skeletal growth and development.
4- Sometimes it is used because the patient suffer from trismus or cannot tolerate the placement of an intraoral film due to the presence of swelling or due to having a gagging sensation .
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ORAL -CLASSIFICATION OF EXTRATECHNIQUES :
I-lateral views:
1- lateral oblique view (body projection and ramus projection)
2- True ∕ Dead lateral view
3- lateral cephalometric view
II-Postero-anterior views :
1- True PA view
2- Sinus view
3- Reverse Towne’s view 9 Dr.Mohammed Shamiah
III-Antero-posterior views:
1-True AP view
2-Towne’s view
3-Submentovertex view
IV-TMJ views:
1- Transpharyngeal view
2- Transcranial view
3- Transorbital view
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GENERAL PROCEDURE GUIDELINE: DURING EXTRA ORAL RADIOGRAPHY:
Equipment preparation:
1- Load the extra oral cassette in the darkroom under safelight conditions. place one extra oral film between two extra oral screen and securely close the cassette .
2- Set the exposure factor according to the area to be radio-graphed and according to the patient’s specifications .
Patient preparation:
1- Remove all objects from the head and neck region that may interfere with film exposure.
2- Place a lead apron without a lead collar over the patient and secure it.
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:LATERAL VIEWS -I
1- Lateral oblique view
(body projection and ramus projection)
2- True ∕ Dead lateral view
3- Lateral cephalometric view
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LATERAL OBLIQUE VIEW: -1
- Indications:
• Fracture in the body, angle, ramus or coronoid process.
• Large pathological lesions in the body or ramus.
• Salivary gland stones.
• Impacted lower third molar.
• Used as alternative when intraoral views are unobtainable because of sever gagging or inability to open his mouth.
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LATERAL OBLIQUE VIEW:
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• Ramus projection
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• Body projection
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• Mandibular Body projection
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Central ray: 2 cm below
angle of the mandible (tube
side) towards molar area .
V.A.= -5 to -100
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• Mandibular Ramus projection
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2
2 cm below lower border of the mandible at
the 1st molar area towards the center of the
ramus. V.A. = -15 to -250 Dr.Mohammed Shamiah
:TRUE LATERAL PROJECTION -2
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- indications:
• Lateral profile of the skull.
• Fracture of the outer and inner plates of frontal sinuses.
• Relationship of the maxilla and mandible.
• Posterior displacement of maxillary fracture.
• Foreign bodies in the Oro-pharynx.
• Detects developmental anomalies.
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Lateral Head
Film parallel to
sagittal plane of
the head
The x-rays directed at right
angles to the plane of the film 20 Dr.Mohammed Shamiah
• V.A. = zero degree
• Focal spot-film distance =36 inches
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VIEW: CEPHALOMETRICLATERAL -3
- Indications: 1-it is standardized technique ,used mainly for
orthodontic analysis and assessment of treatment .to assess relationship of the teeth to the jaw and the jaw to the rest of facial skeleton.
2-it is used in orthognathic surgeries in pre and post treatment record.
3-it is used to evaluate facial growth and development, trauma, disease and development anomalies .
4- it is used to evaluate fracture of the cranium and displacement of maxilla.
5- it is used to evaluate condition affecting the skull vault and the sella turcica .
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V.A. = zero degree
Focal spot-film distance = 60 inches Dr.Mohammed Shamiah
26 AN EXAMPLE OF A CEPHALOSTAT
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ANTERIOR VIEWS :-POSTERO-II
1- True PA view and ceph.
2- Sinus view
3- Reverse Townes view
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TRUE PA VIEW: -1
- indications:
• Localizing objects in mediolateral
direction.
• Fractures in maxilla and mandible
specially in anterior region, angle of
mandible, and sub-condylar area.
• Large pathological lesions and
impaction.
• Good visualization of facial st.
including frontal & ethmoidal
sinuses.
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V.A. = zero degree
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WATER’S (SINUS) VIEW: -2
- Indications:
• Examination of para-nasal
sinuses (frontal, ethmoidal,
sphenoidal, and maxillary).
• Examination of nasal bones
and nasal cavity.
• Assessment of coronoid
process fractures.
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REVERSE TOWNE’S VIEW :-3 (OPEN MOUTH)
- indications:
• Suspection of condylar neck
fracture and displacement of
the condyle.
• Show condylar neck and
process and ramus area.
• Reveals the posterolateral wall
of maxillary antrum.
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POSTERIOR VIEWS:-ANTERO-III
1. True antero-posterior view.
2. Towne’s view.
3. Submento vertex view.
4. Trans-orbital TMJ view.
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TRUE AP VIEW:-1
• The X-ray beam passes from
anterior to a posterior
direction through the skull .
• In this situation, the object-film
distance is increased, thus the
magnification is increased
and the sharpness is
decreased, that’s why this
view is not practical ..except
in cases of unconscious
patient where posteranterior
projection is difficult to be
obtained. 35 Dr.Mohammed Shamiah
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TOWNE’S VIEW:-2 (MODIFIED AP OR FRONTO-OCCIPITAL)
- Indications:
• Show the angles and
ramus of mandible.
• Detect subcondylar or
zygomatic arch fractures.
• Show the occipital region.
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V.A. = 30 degrees Dr.Mohammed Shamiah
SUBMENTOVERTEX VIEW-3
- Indications:
• Zygomatic arches fractures.
• Lesions affecting the palate,
pterygoid region or base of
the skull.
• Identify the position and
orientation of the condyles,
body of mandible and
foramina in the base of the
skull.
• Assessment of mediolateral of
mandible before osteotomy. 39 Dr.Mohammed Shamiah
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TMJ VIEWS:-IV
1- Trans-Cranial view. (lateral projection)
2- Trans-Pharyngeal view. (lateral
projection)
3- Trans -Orbital view. (AP projection)
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CRANIAL VIEW-TRANS-1
• This view is taken in the open and closed mouth position to
show the lateral aspect of the condyler head, glenoid fossa,
articular eminence and joint space .
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intraoral
central ray enters 2” above, ½” behind EAM
Transcranial TMJ
floor
MSP
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PHARYNGEAL VIEW -TRANS -2
• This view is used is taken in the open position only to show the medial aspect of the condyler head and neck and articular surface .
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TRANS ORBITAL VIEW-3
• This view is taken in the open position only to
show the entire mediolateral aspect of the condylar head and neck and the articular surface in an anterior (frontal) plane and is
very useful an detecting condylar neck fracture.
• Its rarely used because of the risk of damaging the lens of the eye by radiation.
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•Thank you
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