What is X-RAY SACRO ILIAC JOINT LAT?

The AP sacrum projection is part of the sacroiliac series that includes an oblique projection (PA/AP) of the joint on both sides. Although usually taken as an AP projection it can also be taken PA with a reverse caudal central ray angulation of 30° to 35° when patients cannot assume a supine position.

Patient position

• patient positioned supine on the imaging table with legs extended
• patient’s shoulders and anterior superior iliac spine are at equal distances from the imaging table to prevent rotation

Technical factors

• Anteroposterior projection
• Centering point
  • central ray midline 5 cm below the level of the anterior superior iliac spine (4 cm above the symphysis pubis)
  • central ray with cephalad angle of 30° (male) to 35° (female)
• Collimation
  • laterally to include both sacroiliac joints
  • superiorly and inferiorly to include the entire sacrum
• Detector Size
  • 18 cm x 24 cm
• Exposure
  • 75 kVp
  • 20-30 mAs
• SID
  • 100 cm
• Grid
  • Yes