Which portion of the x-ray beam is most perpendicular to the body part being examined?

The central portion of the x-ray beam is most perpendicular to the body part being examined because it is the part of the beam that is intended to provide the clearest and most accurate imaging of the target anatomy. When the central ray is aligned properly—perpendicular to the imaging receptor and the structure being studied—it reduces distortion and provides optimal image detail.

In radiographic imaging, the central ray is the ideal point of projection; it minimizes the effects of geometric distortion and ensures that the anatomy is imaged uniformly, allowing for the best diagnostic quality. This is particularly important for identifying pathologies or abnormalities, as well as for maintaining the integrity of anatomical measurements in radiographs.

Other portions of the beam, such as peripheral, angled, or oblique rays, do not achieve this optimal projection and can lead to image distortion, making interpretation more challenging.