Which line should be placed parallel to the plane of the IR for the SMV projection?

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 09 Nov 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.

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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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Lateral Projection: Skull
PATIENT POSITION

*Patient is positioned in an RAO or LAO, supported by flexed knee and arm.
*Instruct patient to rest the ear on the table.

Lateral Projection: Skull
PART POSITION

MSP is placed parallel to the IR.
Interpupillary line is perpendicular to the IR.
IOML is parallel with the transverse axis of the IR and perpendicular to the IR's front edge.

Lateral Projection: Skull
CR

CR, perpendicular
enters 2 inches (5 cm) superior to the EAM.

PA Projection: Skull
PATIENT POSITION

Patient is positioned prone or upright, facing a vertical Bucky
Instruct patient to rest forehead on the vertical Bucky.

PA Projection: Skull
PART POSITION

MSP is placed perpendicular to the IR
OML is perpendicular to the IR

CR, perpendicular to the IR
enters MSP of posterior surface and exits at the level of the nasion.

PA Projection: Skull
IMAGE EVALUATION

Demonstrates the orbits filled by the petrous pyramids

PA Axial Projection: Skull (Caldwell Method)
PATIENT POSITION

Patient is positioned prone or upright, facing a vertical Bucky
Instruct patient to rest forehead on the vertical Bucky.

PA Axial Projection: Skull (Caldwell Method)
PART POSITION

MSP is placed perpendicular to the IR
OML is perpendicular to the IR.

PA Axial Projection: Skull (Caldwell Method)
CR

CR, angled 15 degrees caudad
enters MSP of posterior surface and exits at the level of the nasion

PA Axial Projection: Skull (Caldwell Method)
EVALUATION

Demonstrates the petrous ridges in the inferior third of the orbit

AP/AP axial: Skull
PATIENT POSITION

Patient is positioned supine or upright facing x-ray tube

AP/AP Axial Projection: Skull
PART POSITION

MSP is placed perpendicular to the IR
OML is perpendicular to the IR

AP/AP Axial Projection: Skull
CR

AP – CR is perpendicular
AP axial – CR is angled 15 degrees cephalad
Enters MSP of anterior surface at the level the nasion.

AP/AP Axial Projection: Skull
EVALUATION

Demonstrates same anatomy as PA/PA axial projections, except orbits are more magnified due to increased OID

AP Axial Projection: Skull (Towne Method)
PATIENT POSITION

Patient is positioned supine or upright, facing the x-ray tube

AP Axial Projection: Skull (Towne Method)
PART POSITION

MSP is placed perpendicular to the IR
OML is perpendicular to the IR
or
IOML is perpendicular to the IR.

AP Axial Projection: Skull (Towne Method)
CR

CR is angled 30 degrees caudad if OML is perpendicular.
CR is angled 37 degrees caudad if IOML is perpendicular.
CR enters MSP of anterior surface about 2½ inches above the glabella and exits at the level of the foramen magnum.

AP Axial Projection: Skull (Towne Method)
EVALUATION

Shows a symmetric petrous pyramids, the posterior portion of the foramen magnum, the dorsum sellae and posterior clinoids projected within the foramen magnum, the occipital bone, and the posterior parietal bones

PA Axial Projection: Skull (Haas Method)
PATIENT POSITION

Patient is positioned prone or upright, facing the vertical grid device
Instruct patient to rest forehead on the table or vertical grid device

PA Axial Projection: Skull (Haas Method)
PART POSITION

MSP is placed perpendicular to the IR
OML is perpendicular to the IR.

PA Axial Projection: Skull (Haas Method)
CR

CR, angled 25 degrees cephalad
enters the MSP on the posterior surface at a point 1½ inches below the external occipital protuberance (inion) and
exits about 1½ inches above the nasion.

PA Axial Projection: Skull (Haas Method)
EVALUATION

Shows occipital region of the cranium, symmetric petrous ridges and the dorsum sellae and posterior clinoids within the foramen magnum

SMV Projection: Skull (Schüller Method)
PATIENT POSITION

Patient is positioned supine or upright, facing the x-ray tube.
If the supine position is used, the patient's body must be elevated sufficiently to allow full neck extension
Instruct patient to look straight up and rest top of head on table/vertical grid device.

SMV Projection: Skull (Schüller Method)
PART POSITION

MSP is placed perpendicular to the IR
IOML is parallel to the IR.

SMV Projection: Skull (Schüller Method)
CR

CR, perpendicular to the IOML
enters the MSP of the throat between the mandibular angles and passes through a point 3/4 inch anterior to the level of the EAM.

SMV Projection: Skull (Schüller Method)
EVALUATION

Shows symmetric petrous pyramids, the mastoid processes, foramina ovale and spinosum, carotid canals, the sphenoidal and ethmoidal sinuses, the mandible, the bony nasal septum, the dens of the axis, and the occipital bone

Lateral Projection: Facial Bones
PATIENT POSITION

Patient is positioned in an upright or recumbent RAO or LAO
Instruct patient to rest the ear on the IR.

Lateral Projection: Facial Bones
PART POSITION

MSP is placed parallel to the IR.
Interpupillary line is perpendicular to the IR.
IOML is parallel with the transverse axis of the IR and perpendicular to the IR front edge.

Lateral Projection: Facial Bones
CR

CR, perpendicular
enters at zygomatic bone, halfway between the outer canthus and the EAM.

Lateral Projection: Facial Bones
EVALUATION

Parietoacanthial Projection: Facial Bones (Waters Method)
PATIENT POSITION

Patient is positioned upright, facing the IR, or prone
Instruct the patient to rest the chin on the IR.

Parietoacanthial Projection: Facial Bones (Waters Method)
PART POSITION

MSP is placed perpendicular to the IR
Hyperextend the neck so that the OML forms a 37-degree angle with the plane of the IR.
The MML is approximately perpendicular to the plane of the IR.

Parietoacanthial Projection: Facial Bones (Waters Method)
CR

CR, perpendicular
enters MSP of posterior surface and exits through the acanthion.

Parietoacanthial Projection: Facial Bones (Waters Method)
EVALUATION

Lowers the petrous ridges to demonstrate the orbits, maxillae, and zygomatic arches

Acanthioparietal Projection: Facial Bones (Reverse Waters method)
PATIENT POSITION

Patient is positioned supine.

Acanthioparietal Projection: Facial Bones (Reverse Waters method)
PART POSITION

MSP is placed perpendicular to the IR

Hyperextend the neck so that the OML forms a 37-degree angle with the plane of the IR.
MML is approximately perpendicular to the plane of the IR.

Acanthioparietal Projection: Facial Bones (Reverse Waters method)
CR

CR is perpendicular
enters the acanthion.

Acanthioparietal Projection: Facial Bones (Reverse Waters method)
EVALUATION

Lowers the petrous ridges to demonstrate the orbits, maxillae, and zygomatic arches

PA Axial Projection: Facial Bones (Caldwell Method)
PATIENT POSITION

Patient is positioned prone or upright, facing a vertical Bucky.Maximizes
Instruct patient to rest face, on forehead, on the IR.

PA Axial Projection: Facial Bones (Caldwell Method)
PART POSITION

MSP is placed perpendicular to the IR.
OML is perpendicular to the IR

PA Axial Projection: Facial Bones (Caldwell Method)
CR

CR, angled 15 degrees caudad
enters the MSP of the posterior surface and exits at the level of the nasion.

PA Axial Projection: Facial Bones (Caldwell Method)
EVALUATION

Demonstrates the petrous ridges in the inferior third of the orbits, orbital rims, maxillae, nasal septum, zygomatic bones, and anterior nasal spine

Lateral Projection: Nasal Bones

PATIENT POSITION

Patient is positioned in an upright or recumbent RAO or LAO
Instruct patient to rest the ear on the IR.

Lateral Projection: Nasal Bones
PART POSITION

MSP is placed parallel to the IR.
Interpupillary line is perpendicular to the IR.
IOML is parallel to the transverse axis of the IR and perpendicular to the IR's front edge.

Lateral Projection: Nasal Bones
CR

CR, perpendicular
enters the bridge of the nose at a point ½ inch distal to the nasion

Lateral Projection: Nasal Bones
EVALUATION

SMV Projection: Zygomatic Arches
PATIENT POSITION

Patient is positioned supine or upright, facing x-ray tube.
If supine position is used, the patient's body must be elevated sufficiently to allow full neck extension
Instruct patient to look straight up and rest top of head on table/vertical grid device.

SMV Projection: Zygomatic Arches
PART POSITION

MSP is placed perpendicular to the IR.
IOML is parallel to the IR.

SMV Projection: Zygomatic Arches
CR

CR, perpendicular to the IOML
enters the MSP of the throat about 1 inch posterior to the outer canthi.

SMV Projection: Zygomatic Arches
EVALUATION

Shows bilateral symmetric SMV images of the zygomatic arches projected free of superimposed structures

Tangential Projection: Zygomatic Arch
PATIENT POSITION

Patient is positioned supine or upright, facing x-ray tube.
If supine position is used, the patient's body must be elevated sufficiently to allow full neck extension
Instruct patient to look straight up and rest top of head on table/vertical grid device.

Tangential Projection: Zygomatic Arch
PART POSITION

IOML is parallel to the IR.
Rotate MSP 15 degrees toward the arch of interest.
Tilt the top of the head 15 degrees away from the arch of interes

Tangential Projection: Zygomatic Arch
CR

CR, perpendicular to IOML
enters the zygomatic arch approximately 1 inch posterior to the outer canthus.

Tangential Projection: Zygomatic Arch
EVALUATION

Shows unilateral tangential images of the zygomatic arch projected free of superimposed structures

AP Axial Projection: Zygomatic Arches (Modified Towne Method)
PATIENT POSITION

Patient is positioned supine or upright, facing x-ray tube
Instruct patient to look straight ahead

AP Axial Projection: Zygomatic Arches (Modified Towne Method)
PART POSITION

MSP is placed perpendicular to the IR
OML is perpendicular to the IR orIOML is perpendicular to the IR.

AP Axial Projection: Zygomatic Arches (Modified Towne Method)
CR

CR is angled 30 degrees caudad if OML is perpendicular.
CR is angled 37 degrees caudad if IOML is perpendicular.
CR enters MSP at glabella, approximately 1 inch above the nasion

AP Axial Projection: Zygomatic Arches (Modified Towne Method)
EVALUATION

Shows symmetric AP axial projection of both zygomatic arches projected free of superimposition

PA Projection: Mandibular Rami
PATIENT POSITION

Patient is positioned prone or upright, facing IR.
Instruct patient to rest forehead on IR/table

PA Projection: Mandibular Rami
PART POSITION

MSP is placed perpendicular to the IR.
OML is perpendicular to the IR.

PA Projection: Mandibular Rami
CR

CR, perpendicular
exits at the level of the acanthion.

PA Projection: Mandibular Rami
EVALUATION

Shows mandibular rami and body for demonstration of medial or lateral displacement of fragments in rami fracture

PA Axial Projection: Mandibular Rami
PATIENT POSITION

Patient is positioned prone or upright, facing IR.
Instruct patient to rest forehead on IR/table.

PA Axial Projection: Mandibular Rami
PART POSITION

MSP is placed perpendicular to the IR
OML is perpendicular to the IR.

PA Axial Projection: Mandibular Rami
CR

CR, angled 20 or 25 degrees cephalad,
exits at the acanthion.

PA Axial Projection: Mandibular Rami
EVALUATION

Shows mandibular rami and body for demonstration of medial or lateral displacement of fragments in rami fracture

Axiolateral and Axiolateral Oblique Projections: Mandible
PATIENT POSITION

Patient is recumbent or upright, facing IR with body in an anterior oblique position to place side of interest closer to IR
Extend neck to place body of mandible parallel to transverse axis of IR.

Axiolateral and Axiolateral Oblique Projections: Mandible
PART POSITION

Three different head positions are used to demonstrate different portions of the mandible:

• Ramus – lateral position (left image)
• Body – rotated 30 degrees toward the IR (middle image)
• Symphysis – rotated 45 degrees toward the IR (right image)

Axiolateral and Axiolateral Oblique Projections: Mandible
CR

CR, angled 25 degrees cephalad
exits mandible

AP Axial Projection: TMJ

PATIENT POSITION

Patient is supine or upright, facing the x-ray tube with back of head in contact with IR.

AP Axial Projection: TMJ
PART POSITION

MSP is perpendicular to IR
OML is perpendicular to IR.

AP Axial Projection: TMJ
CR

CR, angled 35 degrees caudad
enters MSP 3 inches (7.6 cm) above the nasion.

AP Axial Projection: TMJ
EVALUATION

Shows the mandibular condyles and the mandibular fossae of the temporal bones

Axiolateral Oblique Projection: TMJ
PATIENT POSITION

Patient is upright or semiprone with body in an anterior oblique position
cheek resting on IR/table

Axiolateral Oblique Projection: TMJ
PART POSITION

Center a point ½ inch anterior to EAM to the IR
Rotate MSP of the head 15 degrees toward the IR.

Interpupillary line is positioned perpendicular to the plane of the IR
Adjust neck flexion to position the AML parallel to the transverse axis of the IR.

Axiolateral Oblique Projection: TMJ
CR

CR, angled 15 degrees caudad
enters about 1½ inches superior to the EAM not on the IR and exits through the TMJ closest to the IR

Axiolateral Oblique Projection: TMJ
EVALUATION

Lateral Projection: Paranasal Sinuses
PATIENT POSITION

Patient is positioned in an upright or RAO or LAO.
Instruct patient to rest the ear on the IR.

Lateral Projection: Paranasal Sinuses
PART POSITION

MSP is placed parallel to the IR
Interpupillary line is perpendicular to the IR.
IOML is positioned horizontally and perpendicular to the IR's front edge.

Lateral Projection: Paranasal Sinuses
CR

CR, horizontal and perpendicular
enters ½ to 1 inch posterior to the outer canthus.

Lateral Projection: Paranasal Sinuses
EVALUATION

Shows the AP and superoinferior dimensions of all four sets of paranasal sinuses, their relationship to surrounding structures, and the thickness of the outer table of the frontal bone

PA Axial Projection: Paranasal Sinuses (Caldwell Method)
PATIENT POSITION

Patient is positioned upright, facing vertical grid device.

PA Axial Projection: Paranasal Sinuses (Caldwell Method)
PART POSITION

MSP is placed perpendicular to the IR.

Position the patient's head so that the OML forms a 15-degree angle with the horizontal CR.
Support position of OML with a sponge between the forehead and the grid device

PA Axial Projection: Paranasal Sinuses (Caldwell Method)
CR

CR, horizontal and perpendicular to the IR
enters the MSP of posterior surface and exits at the level of the nasion

PA Axial Projection: Paranasal Sinuses (Caldwell Method)
EVALUATION

Demonstrates the frontal sinuses and the anterior ethmoid air cells

Parietoacanthial Projection: Paranasal Sinuses (Waters Method)
PATIENT POSITION

Patient is positioned upright, facing vertical grid device
Instruct patient to rest chin on the IR.

Parietoacanthial Projection: Paranasal Sinuses (Waters Method)
PART POSITION

MSP is placed perpendicular to the IR.
Hyperextend the neck so that the OML forms a 37-degree angle with the plane of the IR.
MML is approximately perpendicular to the plane of the IR.

Parietoacanthial Projection: Paranasal Sinuses (Waters Method)
CR

CR, horizontal and perpendicular
enters MSP of posterior surface and exits through the acanthion.

Parietoacanthial Projection: Paranasal Sinuses (Waters Method)
EVALUATION

Lowers the petrous ridges to demonstrate the maxillary sinuses without bony superimposition

Parietoacanthial Projection: Paranasal Sinuses (Open-Mouth Waters Method)
PATIENT POSITION

Patient is positioned upright, facing vertical grid device
Instruct patient to rest chin on the IR.

Parietoacanthial Projection: Paranasal Sinuses (Open-Mouth Waters Method)
PART POSITION

MSP is placed perpendicular to the IR
Hyperextend the neck so that the OML forms a 37-degree angle with the plane of the IR.
MML is approximately perpendicular to the plane of the IR. Instruct patient to open his or her mouth wide while maintaining the position of the head

Parietoacanthial Projection: Paranasal Sinuses (Open-Mouth Waters Method)
CR

CR, horizontal and perpendicular
enters MSP of posterior surface and exits through the acanthion

Parietoacanthial Projection: Paranasal Sinuses (Open-Mouth Waters Method)
EVALUATION

Demonstrates the sphenoid sinus through the open mouth

SMV Projection: Paranasal Sinuses

PATIENT POSITION

Patient is positioned upright, facing x-ray tube
Instruct patient to look straight up and rest top of head on table/vertical grid device

SMV Projection: Paranasal Sinuses
PART POSITION

MSP is placed perpendicular to the IR
IOML is parallel to the IR

SMV Projection: Paranasal Sinuses
CR

CR, horizontal and perpendicular to IOML
enters MSP approximately 3/4 inch anterior to the EAM

SMV Projection: Paranasal Sinuses
EVALUATION

Shows sphenoid sinuses and ethmoid air cells

What is placed parallel to the IR in SMV projection?

Which positioning line is parallel to the IR for the SMV projection for the cranium?

Which plane of the head is placed parallel to the plane of the image receptor for a lateral projection of the skull?

Which 2 positioning lines or planes should be perpendicular to the IR for the PA projection of the skull?