Skull - TownesThis is a featured page

Radiographic Positioning


Adult
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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
Portrait
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
Positioning
  • 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
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 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
Collimation
  • 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
Exposure
  • 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.



AndyC
AndyC
Latest page update: made by AndyC , Jun 14 2011, 8:55 PM EDT (about this update About This Update AndyC Edited by AndyC

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11B skull towns 1 Jan 9 2009, 10:30 PM EST by Anonymous
Thread started: Jan 9 2009, 3:56 PM EST  Watch

The use of the "shoulder' filter placed in the field across the apex of the skull considerably enhanses the final image. This filter also produces good results when doing sinuses. Those of you who are unfamiliar with the shoulder filter, it is a rectangular block of aluminium 11mm thick with a semi circular scalope removed from the lower edge. It is designed to produce an even image of the shoulder from the glenoid to the outer shot tissue. This it does very well, but I also use it for skull & sinus examinations. Mine is the Grey-Tech F700 but I am sure there are other manufacturers in other parts of the world with their own version.
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