When using a 35x43 cm image receptor for an AP projection of the lumbar spine, where should the central ray enter the patient?

For an anterior-posterior (AP) projection of the lumbar spine using a 35x43 cm image receptor, the central ray should enter at the level of the iliac crest. This is because the iliac crest corresponds with the L4-L5 vertebral interspace, which is centrally located within the lumbar region. By positioning the central ray here, the radiographer ensures that the entire lumbar spine is included in the image, from the L1 vertebra down to the sacrum.

The iliac crest serves as a reliable anatomical landmark for this projection, as it is easily palpated on most patients, allowing for consistent positioning. This technique helps to obtain an optimal view of the lumbar vertebrae, allowing for accurate assessment and diagnosis of any potential issues.

In contrast, other landmarks such as the xiphoid process, L2-L3, or the pubic symphysis do not provide adequate coverage of the lumbar spine in the AP view. The xiphoid process is located too high, likely missing the lower lumbar vertebrae, while targeting L2-L3 is too superior and would not capture the full extent of the lumbar region. The pubic symphysis is much lower, potentially including unnecessary structures