Extra oral radiographic techniques

Extra-oral radiographic techniques
Presenter – Dr. Ruchika Garg

References
1. Oral radiology : 5th Edition : White & Pharoah
2. Dental & maxillofacial radiolgy : Freny Kharodjkar
3. Essential of dental radiogrpahy & radiology : 3rd Edition : Eric Whaites
4. Shivlal Rawlani, Shobha Rawlanl, Mukta Molwani, Shirish Degwekar, Rahul Bhowle, Rakhi
Baheti. Imaging Modality for Temporomandibular Joint Disorder - A Review. J Datta Meghe Inst
Med Sci , 2010.
5. Hye Jin Baek et al. Identification of Nasal Bone Fractures on Conventional Radiography and Facial
CT: Comparison of the Diagnostic Accuracy in Different Imaging Modalities and Analysis of
Interobserver Reliability. Iranian Journal of Radiology. 2013 September; 10(3): 140-7.
6. V Sharma, D Chaudhary, R Mitra. Prevalence Of Ponticulus Posticus In Indian Orthodontic
Patients. Dentomaxillofac Radiol 2010 Jul;39(5):277-83

Introduction
Extra oral radiography means that the source as well as film are placed outside the mouth
& an exposure is made in order to obtain the images on a recording medium.
Extra oral radiography provides wider anatomic coverage on a single film.

Indications
Placement of intraoral films is not possible as during trismus.
To examine the extent of large lesions, especially when the area of pathology is greater
than which can be covered by an intraoral periapical film.
When jaws or other facial bones have to be examined for evidence of disease lesions
and other pathological conditions.
To evaluate skeletal growth and development.
To evaluate the status of impacted teeth.
To evaluate trauma.
To evaluate temporomandibular joint area

Drawbacks
• Magnification occurs due to the greater object to film distance.
• Details are not well-defined due to the use of cassettes and intensifying screens.
• For optimum balance between loss of image detail and reduction of patient exposure ,
medium speed screen film combinations should be used.
• Contrast is reduced as the secondary radiation produced by the soft tissues is more.

Definition of Some Extraoral Landmarks used for
Patient Positioning
The Median Plane of the Head (Mid-sagittal Plane)
• This is determined by a line that is coincident with the sagittal suture between the upper
margins of the parietal bones running from the top of the skull backwards.
• In the lateral views the median plane is kept parallel with the cassette.
• In the postero-anterior views, it is kept at right angles with the film cassettes.

The Orbito-meatal Line (Cantho-meatal Line)
• This is an imaginary line from the outer canthus of the eye to the tragus of
the ear.
• This is known as the radiographic base line

The Frankfort Horizontal Line
• Is the line which runs from the most inferior portion of infraorbital margin
of the orbit to the highest point on the superior surface of the external
auditory meatus

Types
A. Radiography of Paranasal Sinuses
Posteroranterior Projection
a) Postero-anterior ( Granger) projection
b) Modified method - Inclined Postero-anterior ( Caldwell ) projection
B. Radiography of the Maxillary Sinuses
a) Standard occipitomental projection ( 00 OM )
b) Modified method ( 30o OM )
c) PA Water’s
C. Radiography of the Mandible
a) PA Mandible
b) Rotated PA Mandible
c) Lateral Oblique
Body of mandible
Ramus of mandible

Types
D. Radiography of Base of the Skull
Submento Vertex projection
E. Radiography of the Zygomatic Arches
Jughandle view ( A Modification of submento - vertex view )
F. Radiography of the Temporomandibular Joint
a) Transcranial Projection
b) Trans Pharyngeal Projection
c) Trans Orbital Projection
d) Reverse Towne's Projection
G. Radiography of the Skull
a) Lateral cephalogram
b) True lateral
c) PA cephaloaram
d) Towne’s projection

Radiography of the Paranasal Sinuses

Postero - anterior ( Granger projection )
Indications :
• The skull for trauma or developmental
abnormalities.
• For detecting progressive changes in the
mediolateral dimensions of the skull, including
asymmetric growth.
• Offers good visualization of facial structures,
including the frontal and ethmoid sinuses, nasal
fossae, and orbits.
• Upper part of antrum is superimposed by dense
shadow of petrosae

Film Placement
• The cassette is placed perpendicular to the floor in a cassette holding device.
• Long axis of cassette is positioned vertically
Head Position
• The patient faces the cassette, the forehead and the nose both touching the
cassette ( mid-sagittal plane perpendicular to the plane of cassette )
Projection of central ray
• The central ray is directed to the midline of the skull
• X-ray beam passes through the canthomeatal plane perpendicular to the film plane.
Exposure parameters :
• kVp : 70-80 & mA : 50-60 & Sec : 1.6

Postero - anterior ( Caldwell projection )
Indications :
• Offers better visualization of
orbits and ethmoid air cells.
• Maxillary sinuses are
superimposed by dense
shadow of petrosae

Film Placement
• Similar to Granger projection
Head Position
• Similar to Granger projection
• The central ray is directed 23ᵒ to the horizontal centered through the lower
border of orbit.
kVp : 70-80 & mA : 50-60 & Sec : 1.6

Puffed cheek view
• Sialoliths in the distal portion of Stensen’s duct or in the parotid gland are difficult to
demonstrate by intraoral views.
• However, a PA skull projection with the cheeks puffed out may move the image of the
sialolith free of the adjacent bone, rendering it visible on the projected image.
kVp : 70-80 & mA : 50-60 & Sec : 0.5

Radiography of the Maxillary Sinuses

Standard Occipitomental Projection ( 00 OM)
Indications
• Middle 3rd fractures i.e.,
Le Fort I
Le Fort II
Le Fort III
• Zygomatic complex
• Nasoethmoidal complex
• Orbital blow out &
• Coronoid fractures

Film placement :
• The cassette is placed 90o to the floor in a cassette holding device.
• The long axis of the cassette is positioned vertically
Position of the Patient :
• Mid-sagittal plane should be vertical and perpendicular to the plane of casette.
• The patient is positioned facing the film the head tipped back so the radiographic line is
at 450 to the film, the so-called nose - chin position.
Central Ray :
 Horizontal ( 00 centered through the occiput)
kVp : 70-80 & mA : 50-60 & Sec : 1.6

Modified method ( 30o OM )
Indications
• Middle 3rd fractures i.e.,
Le Fort I
Le Fort II
Le Fort III
 Coronoid fractures

Film placement :
• Similar to Standard occipitomental projection ( 00 OM)
• Similar to Standard occipitomental projection ( 00 OM)
Central Ray :
 30 0 to the horizontal ( centered through the lower border of the orbit)
• kVp : 70-80 & mA : 50-60 & Sec : 1.6

PA Water’s View
Indications
• Is particularly useful to demonstrate the maxillary , frontal and ethmoid sinuses.
• The Sphenoidal sinuses can be seen if the patient is asked to open the mouth , where by the
Sphenoidal sinuses are projected on the palate
• The orbit, frontozygomatic suture,
nasal cavity, coronoid process of the
mandible and zygomatic arch are also seen.

Film placement :
• The cassette is placed 90o to the floor in a cassette holding device
• The mid-sagittal plane should be vertical & 900 to the plane of the film.
• The canthomeatal line should be 370 to the plane of the film
• Water’s (1915) specified that the tip of the nose should be 0.5 to 1.5 cm away from the cassette,
Mahoney (1930) found that the petrosal shadows can be correctly placed by adjusting the
canthometal line 370 to the horizontal

Central Ray :
• Is directed 900 & to the mid point of the film.
• It enters from the vertex & exits from the acanthion
Exposure parameters:
• kVp : 70-80 & mA : 50-60 & Sec : 1.6

PA Mandible
Indications:
• Fractures of the mandible involving the:
– Posterior 3rd of the body
– Angles
– Rami
– Low condylar necks
• Lesions such as cysts or tumours in the
posterior 3rd of the body or rami to note
medio-lateral expansion
• Mandibular hypoplasia or hyperplasia
• Maxillofacial deformities

Film placement:
Position of the Patient:
• The sagittal plane should be vertical & 900 to the film
• The head is tipped forward so that radiographic baseline is horizontal and perpendicular
to the film in the forehead-nose position.
Central Ray:
• Is directed at right angles to the film through the mid-sagittal plane
• Centered through the cervical spine at the level of the rami of the mandible
kVp : 65-80 & mA : 60-80 & Sec : 1.6

Rotated PA Mandible
Indications:
• Stones/calculi in the parotid glands
• Lesions such as cysts or tumours in the ramus that may cause medio-lateral expansion
• Submasseteric infections

Film placement :
• The patient is positioned facing the film, with the occlusal plane horizontal and the tip of the nose
touching the film.
• The head is then rotated 100 to the side of interest.

Central Ray :
• Is directed at 900 to the film, aimed down the side of the face which is of
interest.
• kVp : 65-80 & mA : 60-80 & Sec : 1.6

Lateral radiographs
They are categorized into:
1. Lateral oblique
2. Bimolars (two oblique laterals on one film)

Lateral Oblique Projection
For the body of mandible
For the ramus of mandible
Lateral oblique views are commonly used to examine the mandible

Body of the mandible
Structures : Body of the mandible
Position of teeth in the same area
Ramus of the mandible
Angle of the mandible
Film placement :
• The cassette is placed flat against the patient’s cheek & is centered over the body of the
mandible
• Should be positioned parallel to the body of the mandible & inferior border of the
cassette should be parallel to the lower border & below it

Position of the patient:
• The patient head is adjusted such that the ala tragus line is parallel to the floor
• The mandible is protruded slightly to separate it from the vertebral column.
• The sagittal plane is tilted so that it is 50 to the vertical & the head is rotated 10 to 150 from the true
lateral position
• Raise the chin : to increase the triangular space b/n the back of the ramus & the cervical spine ( the
so called radiographic keyhole) through which the X-ray beam will pass
Central ray:
• Is directed from under the mandible opposite the side of examination, from 2 cm below the angle
of the mandible.
• The beam is directed upwards ( -10 to 150 ) & centered on the body of the mandible & directed
900 to the horizontal plane of the film
• kVp: 65 to 75 & mA: 7-10 & Sec.: 0.8

Mandibular ramus projection
• The mandibular ramus projection gives a view of the ramus from the angle of the
mandible to the condyle
• It is often very useful for examining the third molar regions of the maxilla and mandible.
Film Placement
• The cassette is placed against the patients cheek and is centered over the ramus
of the mandible.

Head Position
 The head is tipped approximately 15 degrees toward the side being imaged.
 The chin is extended and elevated slightly.
• The central ray is directed to a point posterior to the third molar region on
the side opposite the cassette ( -15 to -20 degrees )
• kVp : 65 to 75 & mA : 7-10 & Sec. 0.8

Bimolars ( Two oblique laterals on one
film)
• Bimolar is the term used for the radiographic projection showing oblique lateral views
of the right and left sides of the jaws on the different halves of the same radiograph.

The technique can be summarized as follows :
1. The patient is positioned with one side of the face in the middle one half of the cassette.
2. The other half of the cassette is covered by a lead shield to prevent exposure of this side
of the film.
3. The X-ray tubehead is positioned to show the desired area, and the exposure is made.
4. The lead shield is then placed over the other side of the cassette to protect the part of the
film already exposed.
5. The patient is then positioned in a similar manner with the cassette held on the other side
of the face.
6. The X-ray tubehead is re-positioned and a second exposure made.

Radiography of the Base of the Skull

Submento-vertex Projection
Indications
• Destructive/expansive lesions affecting the palate, pterygoid region or base of skull
• Investigation of the sphenoidal sinus
• Assessment of the thickness ( medio – lateral ) of the posterior part of the mandible before
osteotomy
• Fracture of the zygomatic arches — to show these thin bones the SMV is taken with reduced
exposure factors.
Film Placement
• The cassette is placed perpendicular to the floor in a cassette holding device vertically.

Head Position
• The patient’s head and neck are tipped back as far as possible ; the vertex of the
skull touches the cassette.
• Both the mid-sagittal plane and the Frankfurt plane are positioned perpendicular to
the floor.
• The central ray is directed through the center of the head and perpendicular to the
cassette
• kVp : 50 & mA : 20-30 & Sec : 0.4

Radiography of the zygomatic arches

Jughandle view ( A Modification of submento-vertex view )
Structures viewed :
• A symmetrical axial view of zygomatic arches

Film placement :
 Same as in Submento-vertex Projection
Position of the patient :
 Same as in Submento-vertex Projection
Central ray :
 Is brought as close as possible to the patient ( leads to magnification of the
structures at the base of the skull)
• Is approximately 1/3 rd the normal exposure time for a SMV

Radiography of the
Temporomandibular Joint

Transcranial Projection
• The Transcranial view provides a sagittal view of the lateral aspects of the condyle and temporal
component.
• It is useful for identifying gross osseous changes on the lateral aspect of the joint only, displaced
condylar fractures, and range of motion of the joint.
Film Placement
• The cassette is placed flat against the patient’s ear and is centered over the T.M.J.
Head Position
• The mid-sagittal plane must be positioned perpendicular to the floor and parallel with the
cassette.

• The central ray is directed toward a
point 2 inches above and 0.5 inches
behind the opening of the ear canal.
• The beam is directed downward (+25
degrees) and forward (20 degrees) and
is centered on the T.M.J. that is
being imaged.

• Open mouth projection : Ask
patient to open mouth as wide as
possible without unduly straining
muscles
• Closed mouth projection : Ask
patient to close mouth in centric
occlusion or maximal
intercuspation

Transpharyngeal Projection ( Infracranial or McQueen Dell
Technique )
• Provides a sagittal view of the medial pole of the condyle.
• It is effective for visualizing erosive changes of the condyle rather than more subtle
changes.
Film Placement
• The cassette is placed flat against the patient ear and is centered over the T.M.J.
Head Position
• The mid-sagittal plane must be positioned perpendicular to the floor and parallel
with the cassette.

• The central ray passes through the TMJ of the opposite side at a vertical angulation of 0
degrees and is directed posteriorly at an angle of 10 degrees to the coronal section

Transorbital ( Zimmer Projection )
• Provides an anterior view of the TMJ.
• Condylar head and neck is visible, making it particularly useful for visualizing condylar
neck fractures.
Film Placement
• The film is placed behind the head of the patient and at an angle of -30 degrees to the
coronal plane.

Head Position
• The patient’s head is angulated downwards till the canthomeatal line is parallel to the
floor, and the mouth is opened to its maximal opening so that the head of the condyle is
directly under the articular eminence.
• The central ray passes through the center of the orbit of the side of interest, at a vertical
angulation of 10 degrees and strikes the film perpendicular to its plane.

Reverse - Towne’s Projection
• It is used to examine condylar neck fracture, intracapsular fractures of TMJ,
condylar hypoplasia
• The projection is particularly suitable for revealing a medially displaced
condyle.
Virendra Singh, Ajay Verma, Gyanander Attresh, Jitender Batra. Ortho-surgical management of condylar hyperplasia : Rare case
reports. National Journal of Maxillofacial Surgery ; Vol 5 ; Issue 1 ; Jan - Jun 2014. DOI : 10.4103/0975-5950.140180

Film Placement
• The cassette is placed perpendicular to the floor in a cassette holding device vertically.
Head Position
• The patient faces the cassette with the head tipped down and the mouth open as wide as possible.
• The chin rests on the chest while the top of the forehead touches the cassette.
• The mid-sagittal plane must be positioned perpendicular to the floor, and the head is centered
on the cassette.

• The central ray is directed through the mid-sagittal plane at the level
of mandible and is perpendicular to the cassette.

Lateral Cephalogram Projection
• It is used to survey the facial bones for evidence of trauma, disease or developmental abnormality.
• It reveals the nasopharyngeal soft tissues, paranasal sinuses, and hard palate.
• Orthodontists use it to assess facial growth and it is used in oral surgery and prosthodontics to
establish pretreatment and post treatment records.
• The lateral cephalometric projection reveals the facial soft tissue profile but otherwise is identical to
the lateral skull projection.

Film Placement
• The cassette is placed perpendicular to the floor in a cassette holding device horizontally.
Head Position
• The patient’s head is positioned adjacent to the cassette.
• The mid-sagittal plane must be positioned perpendicular to the floor and parallel with the
cassette.
• The Frankfurt plane is positioned parallel with the floor.
• The head is centered over the cassette.
• The patient is asked to keep the teeth in occlusion.

• The central ray is directed through the center of the cassette and perpendicular to the
cassette.
• A wedge filter is placed at the tube head over the anterior aspect of the beam to absorb some of
the radiation & allow visualization of soft tissues of the face.

Case report
V Sharma, D Chaudhary, R Mitra. Prevalence Of Ponticulus Posticus In Indian Orthodontic Patients. Dentomaxillofac Radiol 2010
Jul;39(5):277-83

True Lateral
• The main difference between the true lateral skull and the true cephalometric lateral
skull taken on the cephalostat is that the true lateral skull is not standardized or
reproducible.
• This view is used when a single lateral view of the skull is required but not in
orthodontics or growth studies.
• Indications:
• Fractures of the cranium and the cranial base
• Middle third facial fractures, to show possible downward and backward displacement
of the maxillae
• Conditions affecting the skull vault, particularly:
Paget's disease
Multiple myeloma
Hyperparathyroidism

Film placement :
• The cassette is placed 90o to the floor in a cassette holding device. The long axis of the cassette is
positioned vertically & is parallel to the patient’s midsagittal plane
Position of the patient :
• The sagittal plane should be vertical and parallel to the film.
• The film is adjusted so that the upper circumference of the skull is ½ inch below the upper border
of the cassette.
• The patient is asked to keep his/her teeth in occlusion, and the occlusal plane should be parallel to
the floor.
Central ray :
• Central ray horizontal (0°) and perpendicular to the
sagittal plane and the film, centered through
the external auditory meatus.

PA Cephalogram
• Structures shown : Skull vault
• Facial bones
Indications :
• Trauma, disease or developmental abnormalities
• Investigation of frontal sinuses
• Conditions affecting the cranium
• Intracranial calcifications

Film placement :
• The patient is positioned facing the film with only the tip of the nose touching the film , so that the
radiographic baseline forms 100 with the horizontal plane.
• The sagittal plane should be vertical and perpendicular to the film.
• The film is adjusted so that the lips are centered to the film
Central ray :
• Is perpendicular to the image receptor, directed from the posterior to the anterior , parallel to
patient’s midsagittal plane & is centered at the level of the bridge of the nose.

Towne’s Projection
Structures :
• Primarily used to observe the
occipital area of the skull.
• The necks of the condyle process can
be viewed.
Towne radiographic view of the
left condylar fracture

Film Position :
• The cassette is placed perpendicular to the floor in a cassette holding device.
• The long-axis of the cassette is positioned vertically.
Position of Patient :
• This is an anteroposterior ( AP) view, with the back of the patient's head touching the film.
• The canthomeatal line is perpendicular to the film.
Central ray :
• Is directed at 30° to the canthomeatal line and passes through it at a point between the external
auditory canals.

Others
Lateral Nasal View
Hye Jin Baek et al. Identification of Nasal Bone Fractures on Conventional Radiography and Facial CT: Comparison of the Diagnostic
Accuracy in Different Imaging Modalities and Analysis of Interobserver Reliability. Iranian Journal of Radiology. 2013 September;
10(3): 140-7.

Conclusion
• Selecting the appropriate extra oral radiographic examination is the first step in obtaining and
interpreting a radiograph.
• Before taking an extra oral radiograph , it is essential to evaluate the patient’s complaint and
clinical signs in detail.
• So the anatomic structure to be evaluated should be selected and then the appropriate projection
should be selected.
• Thorough knowledge of the indications of various extra oral techniques allows accurate and timely
diagnosis of various maxillofacial pathologies.

Extra oral radiographic techniques

Extra oral radiographic techniques

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Extra oral radiographic techniques

Semelhante a Extra oral radiographic techniques (20)

Mais de Ruchika Garg

Mais de Ruchika Garg (14)

Último

Último (20)

Extra oral radiographic techniques