Skull (AP view)

Radiopaedia • CC-by-nc-sa 3.0 • de

The skull anteroposterior (AP) view is a non-angled radiograph of the skull. This view provides an overview of the entire skull rather than attempting to highlight any one region.

Indications

This examination is able to assess for medial and lateral displacements of skull fractures, in addition to neoplastic changes and Paget disease.

Note: As this view results in higher radiation dose to the radiosensitive lens of the eyes compared to the PA view, it should only be used in situations where the patient is unable to face the detector, like in trauma settings and patients with poor mobility.

Patient position

  • the back of patient's head is placed against the image detector

Technical factors

  • anteroposterior projection
  • centering point
    • the central ray is centered at the nasion
  • collimation
    • laterally to include soft tissue
    • superiorly soft tissue
  • orientation
    • portrait 
  • detector size
    • 24 cm x 30 cm
  • exposure
    • 75 kVp
    • 8-10 mAs
  • SID
    • 100 cm 
  • grid
    • yes

Image technical evaluation

  • ensure the image is symmetrical and free from any rotation
  • assess the orbital margins and ensure they are similar in appearance 
  • the petrous ridge will overlap the orbits

Practical points

  • make sure that any removable artefacts such as earrings, nose studs/rings, glasses or metal dentures are removed to avoid obscuring the anatomy of interest
Advantages

  • may be necessary in patients who cannot be easily or quickly rotated into the skull PA view

Disadvantages
  • overlap of facial bone structures makes it harder to evaluate the sinuses than with an angled view (e.g. Caldwell view)
  • the AP view increases the radiation dose to the eyes compared with the PA view
  • increased magnification of the facial bones compared with the PA view