Skull - Townes

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Radiographic Positioning

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Name of projection Skull - Townes (also called Skull - AP Axial)
Area Covered Skull , foramen magnum
Pathology shown Fractures and pathologies of the skull
Radiographic Anatomy Skull Radiographic Anatomy
IR Size & Orientation 24 x 30 cm
Film / Screen Combination Regular
(CR and DR as recommended by manufacturer)
Bucky / Grid Moving or Stationary Grid
Filter No
Exposure 80 kVp
20 mAs
FFD / SID 100 cm
Central Ray Directed to 6 cm superior to the glabella (this is typically the hairline)
CR 30° caudal (see note below)
Collimation Outer skin margins of the skull
Markers Superior and Lateral
Marker orientation AP
Shielding Gonadal (check your department's policy guidelines)
Respiration Suspended
  • Patient is in an erect position, either standing or sitting
  • Position the patient so that their back and posterior skull are touching the bucky
  • Bring the patients chin down until the radiographic baseline orbitomeatal line (OML) is parallel to the floor, therefore perpendicular the bucky. If the patient is not able to do this, the central ray angle may have to be increased caudally so that there is a 30 degree angle between the radiographic baseline (OML) and the central ray.
  • Ensure the midsaggital plane is perpendicular to the bucky
  • Ensure the interpupillary line is parallel to the floor

  • 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 petrous ridges are horizontal.
  • The central ray is at 30 degrees to the radiographic baseline, evidenced by
    • The dorsum sellae & posterior clinoid processes are seen in the foramen magnum.
Area Covered
  • Skull, dorsum sellae & posterior clinoid processes seen in the foramen magnum
  • Centre: Just above the foramen magnum
  • Shutter A: Open to include the outer skin margins of the skull laterally
  • Shutter B: Open to include the superior aspect of the skull
  • Assess for adequate penetration of the thickest part of the skull
  • The dorsum sellae and posterior clinoid processes are seen in the foramen magnum
  • Bony trabecular patterns and cortical outlines are sharply defined
  • Soft tissues are visualised
Special Notes Effect of the central ray angle being less than 30 degrees to the radiographic baseline (OML)
The dorsum sellae will project higher. This means that it will project above the foramen magnum, rather than in it.