Saturday, December 20, 2014

X-ray examination of the sacrum taken in AP axial projection, the Pathology and disease of sacrum is demonstrated.

Note: The urinary bladder should be emptied before this procedure begins. Also desirable is to have the lower colon free of gas and fecal material which may require a cleaning enema, as ordered by a doctor.

Technical Factors:

  • Cassette size - 24 x 30 cm or 10 x 12 inches, lengthwise
  • Moving or stationary grid
  • 75 to 80 kV range, mAs 15 (85 to 90 kV and reduction to mAs 8)


  • Use gonadal shielding for males. Ovarian shielding o females is not possible without obscuring area of interest.

Positioning of Patient:

  • Align mid-sagittal plane to CR and midline of table or gird.
  • Ensure no rotation of pelvis exist.

Central Ray:

  • CR angled 15° cephalad, to enter 2 inches or 5 cm superior to pubic symphysis.
  • IR centered to projected CR
  • SID is 40 inches (100 cm)


  • Close four-sided collimation to area of interest.


  • Suspend respiration on expiration.

sacrum radiograph ap axialNote:Radiologic Technologist may require to increase centeal ray angle to 20° cephalad for patients with an apparent greater posterior curvature or hit of the sacrum and pelvis.

The sacrum of the female patients is usually shorter and wider than the males sacrum ( a consideration in close four- sided collimation.)

This sacral x-ray can also be performed in patient prone position with an angulation of 15° caudad necessary to patient condition.

Sacral X-ray Radiographic Criteria:

In Sacral x-ray structure shown should be a nonforeshorted AP projection of sacrum,the Sacroilliac joint and Lumbar 5 to Sacral 1 junction.
If proper patient position indicating no rotation of pelvis, the lower part of the sacrum should be centered in the pelvic opening.
Foreshortening and the pubis and sacral foramina should not be superimposed for correct alignment of sacrum and the central ray.

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