Pelvis AP is a radiography positioning projection of the Pelvis. Supine, legs internally rotated 15-20 degrees unless a hip fracture or dislocation is suspected. SID 40". The centering point is located at midline, midway between the level of the ASIS and the symphysis pubis (about 2 inches [5 cm] inferior to the level of the ASIS). The central ray is perpendicular to the IR at midline, directed midway between the level of the ASIS and the symphysis pubis. Image-quality criteria include entire pelvis visible from iliac crests to ischial tuberosities, femoral heads and proximal femora included. A sample technique is 85 kVp with DR 12.5 or CR 25 mAs, at an SID of 40 inches (102 cm).
Watch the setup
All steps (4)
- Place the patient supine, arms at the sides or across the upper chest, a pillow under the head.
- Align the midsagittal plane to the centerline of the table and the CR.
- Separate the legs and feet, then rotate the feet and entire lower limbs internally 15-20 degrees.
- Ensure the pelvis is not rotated: both ASIS the same distance from the tabletop.
3D anatomy: BodyParts3D, © The Database Center for Life Science. Posed, rendered and labelled by RadTechPrepper. These animations are licensed CC BY-SA 4.0. Credits
Anatomy demonstrated
- Iliac crests and wings.
- Acetabula and hip joints.
- Proximal femoral heads and necks.
- Pubic bones and pubic symphysis.
- Ischial tuberosities.
- Sacroiliac joints.
Patient preparation
- WARNING: do not rotate the legs internally if a hip fracture or dislocation is suspected. Take the image as is, with minimal movement of the affected leg.
- Verify patient identity using two identifiers.
- Remove all radiopaque objects from pelvis and hip region.
- Place the patient supine, arms at the sides or across the upper chest, a pillow under the head.
- Align the midsagittal plane to the centerline of the table and the CR.
- Separate the legs and feet, then rotate the feet and entire lower limbs internally 15-20 degrees.
- Ensure the pelvis is not rotated: both ASIS the same distance from the tabletop.
Position & centering point
At midline, midway between the level of the ASIS and the symphysis pubis (about 2 inches [5 cm] inferior to the level of the ASIS).
Central ray
Perpendicular to the IR at midline, directed midway between the level of the ASIS and the symphysis pubis.
Exposure / technique
- kVp
- 85
- mAs
- DR 12.5 / CR 25
- SID
- 40" (102 cm)
- Notes
- Grid required. Shows entire pelvis and proximal femora. Sample technique: DR 12.5 / CR 25 mAs at 85 kVp, 40 in SID, for a 19 cm part (Merrill's sample chart). Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Entire pelvis visible from iliac crests to ischial tuberosities.
- Femoral heads and proximal femora included.
- Margins of the femoral heads and acetabula visualized through the overlying pelvic structures.
- Pubic bones symmetric without rotation.
- No rotation: iliac alae, ischial spines and obturator foramina symmetric.
- Collimation: includes entire pelvis within margins.
Common errors
- 1 Insufficient internal rotation makes the lesser trochanters visible and foreshortens the necks.
- 2 Pelvic rotation makes acetabula and ischium asymmetric.
- 3 Flexed legs shorten femoral shafts and distort hip joints.
- 4 Off-centered CR excludes pelvis or femora.
- 5 A foreshortened or closed obturator foramen indicates rotation in that direction.
- 6 Off-center, so the entire pelvis and superior femora are not in the collimated field.
Clinical indications
- Pelvic fracture evaluation, without rotating the legs.
- Hip dislocation assessment, without rotating the legs.
- Degenerative disease.
- Bone lesions.