For an anteroposterior (AP) projection of the proximal femur, what anatomical landmark should be aligned with the IR?

In an anteroposterior (AP) projection of the proximal femur, the anterior superior iliac spine (ASIS) is the key anatomical landmark used to align with the image receptor (IR). This alignment is critical because the ASIS provides a consistent reference point for positioning the pelvis and lower limb.

Proper alignment with the ASIS ensures that the proximal femur is correctly positioned to minimize distortion and achieve optimal visualization of the femoral head, neck, and greater trochanter. The pelvis needs to be leveled and the limb rotated appropriately, which is guided by the position of the ASIS. This approach helps in accurately capturing the necessary anatomical details for diagnostic purposes.

In the context of imaging, using the ASIS as a reference helps healthcare professionals assess potential pathologies or discrepancies in the proximal femoral structure and aligns with standard radiographic practices.