Skull - AP

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Radiographic Positioning

Other related pages of interest

Name of projection Skull AP
Area Covered Skull vault superiorly, including the maxilla inferiorly
Pathology shown Fractures 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 75 kVp
20 mAs
FFD / SID 100 cm
Central Ray Directed to the glabella
Parallel to the radiographic baseline (OrbitoMeatal Line)
Collimation Outer skin margins of the skull
Markers Inferior/Lateral
Marker orientation AP
Shielding Gonadal (check your department's policy guidelines)
Respiration Suspended
  • The patient typically presents in a supine position in trauma cases
  • If the patient has not been cleared of a cervical spine injury, do not reposition the patient
  • Angle the central ray so that it is parallel and aligned with the radiographic baseline (OML), and directed to the glabella

  • No rotation is evidenced by
    • The lateral borders of the orbits to the lateral borders of the skull are equidistant on both sides. (see note below)
  • No tilt is evidenced by
    • The petrous ridges are horizontal
Area Covered

  • Skull vault, maxilla
  • Centre: Glabella
  • Shutter A: Open to include the lateral skin margins of the skull
  • Shutter B: Open to include the entire skull superiorly, and the maxilla inferiorly
  • Assess for adequate penetration of the thickest part of the skull, the frontal bone
  • Bony trabecular patterns and cortical outlines are sharply defined
  • Soft tissues are visualised
Special Notes Effect of the central ray being parallel to the radiographic baseline (OML)
  • Petrous ridges will be seen within the orbits

Determining the direction of head rotation
The distance from the lateral border of the orbit to the lateral border of the skull on one side will be decreased on the side the patient is looking to. That is, in a PA position, if the patient is lrotated to the left, then the distance will be smaller on this side when compared with the right side of the skull.)