What is the proper placement of the image receptor (IR) when performing an anteroposterior (AP) projection of the proximal femur?

When performing an anteroposterior (AP) projection of the proximal femur, the placement of the image receptor (IR) is crucial for obtaining a clear and diagnostic image. The correct placement at the top of the IR at the level of the anterior superior iliac spine (ASIS) allows for proper coverage of the proximal femur and hip joint in the radiographic field.

This positioning ensures that the entire proximal femur, including the femoral head, neck, and greater trochanter, is included in the image, which is essential for evaluating pathologies or assessing fractures. Having the IR at the ASIS also aligns it appropriately with the central ray's entry point for the AP projection, maximizing both the image quality and the anatomical relevance of the captured area.

Placing the IR at the other suggested positions would result in insufficient imaging of the proximal femur. For example, positioning it at the knee joint would cut off the important proximal structures, while centering it at mid-femur or at the level of the greater trochanter may not properly align with the anatomical features needing evaluation. Therefore, aligning the top of the IR with the ASIS is the standard and most effective practice for this type of radiographic examination.