Name of projection | Skull - SMV (Submentovertex) (also called Basal) |
Area Covered | This view looks at the base of the skull, including structures such as the foramen ovale, foramen spinosum, and sphenoid sinuses |
Pathology shown | Some pathologies of the base of the skull and sphenoid sinuses |
Radiographic Anatomy | Skull Radiographic Anatomy |
IR Size & Orientation | 24 x 30 cm Portrait |
Film / Screen Combination | Regular (CR and DR as recommended by manufacturer) |
Bucky / Grid | Moving or Stationary Grid |
Filter | No |
Exposure | 70 kVp 20 mAs |
FFD / SID | 100 cm |
Central Ray | Directed to the midsaggital plane at the point midway between the angles of mandible, which is also approximately the point midway between the external auditory meatus (EAMs). Perpendicular to the IR/bucky |
Collimation | Laterally, to the soft tissue margins of the skull, including the mandible and occiput |
Markers | Superior and Lateral Marker orientation AP |
Shielding | Gonadal (check your department's policy guidelines) |
Respiration | Suspended |
Positioning | - The aim is to get the IOML (Infraorbitomeatal Line) parallel to the IR and bucky. The method used to achieve this will depend on the presentation of the patient.
- The following description is for patients who are able to tip their head back, hyperextending their neck, and are able to sit.
- The patient sits in an AP position in front of the upright bucky
- The chin is raised and the head tipped back until the IOML is parallel to the bucky and the vertex of the skull is centred and resting against the bucky.
- If the patient is able to achieve this position then the central ray is perpendicular to both the bucky and the IOML.
- If the patient is unable to tip their head back far enough, then angle the central ray so that it is perpendicular to the IOML.
- Ensure the midsagittal plane is perpendicular to the bucky.
|
Critique
| Positioning - No rotation is evidenced by
- The lateral borders of the foramen magnum are equidistant from the lateral borders of the skull.
- No tilt is evidenced by
- The vomer and the bony nasal septum are aligned with the long axis of the film.
- The central ray is at 90 degrees to the IOML, evidenced by
- The mandibular mentum superimposes the outer border of the frontal bone.
Area Covered - Occiput, foramen magnum, sphenoid sinuses, foramen ovale, foramen spinosum, mandible,
Collimation - Centre: Midway between the EAMs
- Shutter A: Open to include the soft tissue and lateral borders of the skull
- Shutter B: Open to include the mandible superiorly and the occiput of the skull inferiorly
Exposure - Assess for adequate penetration of the thickest part of the skull
- Bony trabecular patterns and cortical outlines are sharply defined
- Soft tissues are visualised
|
Special Notes |
|