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Submentovertex – Extraoral View

In this post we shall discuss about SubmentovertexExtraoral View

Radiograph of the base of the skull is taken by Submentovertex – Extraoral View (SMV).


Indications

Lesions affecting palate or pterygoid region or base of skull or sphenoidal sinus.


Exposure

0.4 Seconds

50 kVp

20-30 mA


Structures Visible in this view

Carotid canals

Nasal septum

Odontoid process or atlas

Mandible

Projection of petrosa

Mastoid process

Foramen Ovale

Spinosum canal

Sphenoidal sinus

Maxillary sinus

Axial inclination of Mandibular condyles


Film Placement

Perpendicular to the floor

Long axis of film/cassette should be placed vertically


Patient Position

Head of the patient is centered on the casette

Head and neck should be tipped back as far as possible

Vertex of skull should touch cassette

Mid sagittal plane should be perpendicular to the film

Radiographic base line is parallel to film


Central Ray

It is directed perpendicular to the film passing through mid sagittal plane.

Central ray should be perpendicular to an imaginary line joining mandibular first molars

For viewing petroud portion, central ray should be at right angles to film midway between the external auditory meatus.