What is the relationship between the coronal plane through the humeral epicondyles and the IR to achieve a proper AP projection of the elbow?

In an anteroposterior (AP) projection of the elbow, the relationship between the coronal plane through the humeral epicondyles and the image receptor (IR) must be parallel. When the coronal plane is parallel to the IR, it ensures that the epicondyles of the humerus are properly positioned and not foreshortened in the image. This alignment is crucial for demonstrating the structural anatomy of the elbow joint distinctly and accurately.

Achieving this parallel alignment allows for a true representation of the joint space, which is essential for diagnostic accuracy. If the IR is not parallel to the coronal plane, the resulting image may misrepresent the anatomy and joint position, potentially leading to diagnostic errors.

Therefore, ensuring that the coronal plane through the humeral epicondyles remains parallel to the IR is fundamental for obtaining a proper AP projection of the elbow, allowing for the best visualization of the elbow joint and surrounding structures.