Where should the central ray be directed for the lateral sacrum projection?

For the lateral sacrum projection, the central ray should be directed at the level of the posterior superior iliac spine (PSIS) and then 2 inches anterior to the posterior aspect of the sacrum. This positioning is crucial because it ensures that the central ray is appropriately aligned to penetrate through the sacrum and capture clear images of the anatomical structures without distortion.

The location of the PSIS serves as a reliable landmark, as it is a bony prominence that aids in consistent and accurate positioning. Directing the central ray 2 inches anterior ensures that it intersects the area of interest effectively, allowing for optimal visualization of the sacrum’s lateral profile. This technique minimizes superimposition of adjacent structures, which can compromise the diagnostic quality of the images.

In terms of projection accuracy, both the height and anterior angulation of the ray are vital. Directing it at other locations, such as the level of L4, S1, or the midline of the body, would not adequately represent the lateral aspect of the sacrum, thus failing to provide the necessary details for assessment and diagnosis.