X-CalibR measurement protocol (AP pelvic radiographs)

Identify Greater Trochanter

  • Set Focal Film Distance (FFD) at 120 cm
  • Use X-CalibR of correct type - see below (“XcalibR models”)
  • Position patient for a standard AP pelvic x-ray as practised in your own radiology department
  • This should involve a method to bring the femoral neck parallel to the CR cassette, e.g.
    • Feet apart with toes touching, or
    • Using a foot box

    Read off mid-point between finger and thumb

  • Identify the Greater Trochanter between finger and thumb (see top picture)
  • Place X-CalibR vertically against the patient
    • For flat table tops: Place X-CalibR directly on the table (see both photos)
    • For dished tables, or for patient on mattress: Place X-CalibR on the table edge
    • If patient lies directly on CR cassette, ie if cassette is between patient and table top place X-CalibR on upper surface of cassette
  • Magnification is given by the marking on X-CalibR’s scale level with a point midway between the anterior and posterior margins of the greater trochanter
  • Annotate the digital film with the magnification
    • i.e. 120RT = 120% over magnification, right hip

X-CalibR was originally developed for calculating the magnification of AP pelvic radiographs, however the principle will work for any body part

Download the protocol

The above protocol is available in PDF format.

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