On a correctly positioned submentovertical image, the mandibular symphysis is:

Warning: Rule out cervical spine fracture or subluxation on trauma patient before attempting this projection.

Pathology Demonstrated:

• Advanced bony pathology of the inner temporal bone structures (skull base) and basal skull fracture are demonstrated.

Technical Factors:

• IR size - 24 x 30 cm (10 x 12 inches), lengthwise.
• Moving or stationary grid
• 75 to 85 kV range
• Small focal spot
• mAs 30

Shielding:

• Shield patient's upper thorax region (shielding neck and thyroid will obscure area of interest).

Patient Position:

Supine

• Remove all metal, plastic, and other removable objects from patient's head.
• Take radiograph with patient in the erect or supine position.
• The erect position, which is easier for the patient, may be done with an erect table or an upright Bucky.
• A wheelchair can also be used in performing this projection.
• A wheelchair offers support for the back and provides greater stability in maintaining the position.

Part Position:

• Raise patient's chin and hyperextend the neck if possible until IOML is parallel to IR. see note.
• Rest patient's head on vertex.
• Align midsagittal plane perpendicular to the midline of the grid or table / bucky surface, thus avoiding tilt and /or rotation.

Supine: With patient in the supine position, extend position, extend patient's head over end of table, and support grid cassette and head as shown, keeping IOML parallel to IR and perpendicular to CR. If table will not tilt, use a pillow under patient's back to allow sufficient neck extension.

Upright Bucky

Erect: If patient is unable to sufficiently extend the neck, compensate by angling the CR to remain perpendicular to the IOML. Depending on the equipment used, the IR also may be angled to maintain the perpendicular relationship with the CR (such as with an adjustable upright Bucky.)
This position is very uncomfortable for the patients in the erect or the supine position; perform it as quickly as possible.

Central Ray:

• CR is perpendicular to infraorbitalmeatal line.
• Center 1 1/2 inch (4 cm) inferior to the mandibular symphysis or midway between the gonions.
• Center image receptor to CR.
• Minimum SID is 40 inches (100 cm).

Collimation:

• Collimate to outer margins of skull.

Respiration:

• Suspend respiration.

Radiographic Criteria:

Structure Shown:

Submentovertex

• Foramen ovale and spinosum, mandible, spenoid and posterior ethmoid sinuses, mastoid processes, petrous ridges, hard palate, foramen magnum, and occipital bone are shown.

Position:

• Correct extension of neck and relationship between IOML and CR as indicated by mandibular condyles projected anterior to petrous pyramids and frontal bone and mandibular symphysis superimposed.
• Mandibular condyles should be parallel to each other as evidenced by no rotation or tilt, as also indicated by equal distance bilaterally from mandibular condyles to lateral border of skull.

Collimation and CR:

• Entire skull should be visualized on the image, with the foramen magnum in the approximate center.
• Collimation borders should be visible on outer margins of skull.

Exposure Criteria:

• Density and contrast are sufficient to clearly visualize outline of foramen magnum.
• Sharp bony margins indicate no motion. 

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Last revised by Amanda Er ◉ on 17 Mar 2022

Citation, DOI & article data

Citation:

Er A, Skull (submentovertex view). Reference article, Radiopaedia.org (Accessed on 25 Dec 2022) https://doi.org/10.53347/rID-77408

The skull submentovertex view is an angled inferosuperior radiograph of the base of skull. As this view involves radiographic positioning that is uncomfortable for the patient and with CT being more sensitive to bony detail, this view is rapidly becoming obsolete.

On this page:

This view is useful in assessing potential pathology from trauma or disease progression to the basal skull structures 1-4, including the foramen ovale, foramen spinosum and sphenoid sinuses.

It is imperative that any cervical spine subluxations or fractures on acute trauma patients is excluded before proceeding with this view.

• depending on how the patient presents
  • erect: patient leans back on a chair with back support, facing away from the upright bucky
  • supine: elevate the shoulders using a firm pillow, allowing the head to tilt backwards
• the neck is hyperextended until
  • the infraorbitomeatal line (IOML) is parallel with the receptor
  • the skull vertex is in contact with the center of the receptor
• ensure the midsagittal plane (MSP) is perpendicular to the receptor

• inferosuperior projection
• centering point
  • 4 cm inferior to the mandibular mental point (see Figure 2)
  • beam exits at skull vertex
• collimation
  • anterior to include mandibular mentum
  • posterior to include occipital bone
  • lateral to include the skin margin
• orientation  
  • portrait
• detector size
  • 24 cm x 30 cm
• exposure
  • 75-80 kVp
  • 20-25 mAs
• SID
  • 100 cm
• grid
  • yes (this can vary departmentally)

• the mandibular mentum should be demonstrated just slightly anterior to the ethmoid sinuses
  • if too far anterior to the ethmoid sinuses, depress the patient's chin or angle more caudal
  • if demonstrated posterior to the ethmoid sinuses, further extend the neck or angle more cephalic
• there should be equal distance between the mandibular rami and the lateral cranial cortex
  • i.e. an increased mandibular ramus-lateral cranial cortex distance on the right side means the patient's head was tilted towards the right

• patients who are supine for this view may become dizzy after a few minutes due to an increased intracranial pressure 4; the erect method may prevent this
• learning your skull anatomy and positioning lines makes reading positioning guides a whole lot easier
• placing a physical side marker can be useful in determining which side is which

References

Related articles: Imaging in practice

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