1-extraoral techniques.pdf

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 intraoral film because they are not

defined or sharp as intraoral 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.

2 Dr.Mohammed Shamiah

• 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 .


• 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.


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.


A GRID DECREASES THE AMOUNT OF SCATTER

RADIATION THAT REACHES THE EXTRAORAL FILM.


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 .


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


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.


:LATERAL VIEWS -I

1- Lateral oblique view

(body projection and ramus projection)

2- True ∕ Dead lateral view

3- Lateral cephalometric view


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.


LATERAL OBLIQUE VIEW:


• Ramus projection

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• Body projection

Dr.Mohammed Shamiah

• 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

Dr.Mohammed Shamiah

• 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.

Dr.Mohammed Shamiah

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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Dr.Mohammed Shamiah

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

Dr.Mohammed Shamiah

ANTERIOR VIEWS :-POSTERO-II

1- True PA view and ceph.

2- Sinus view

3- Reverse Townes view


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

Dr.Mohammed Shamiah

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.


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.


POSTERIOR VIEWS:-ANTERO-III

1. True antero-posterior view.

2. Towne’s view.

3. Submento vertex view.

4. Trans-orbital TMJ view.


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

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

TMJ VIEWS:-IV

1- Trans-Cranial view. (lateral projection)

2- Trans-Pharyngeal view. (lateral

projection)

3- Trans -Orbital view. (AP projection)


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

Dr.Mohammed Shamiah

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 .


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.


•Thank you


1-extraoral techniques.pdf

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