In an AP film of the cervical spine, where should the central ray be centered?

In an anterior-posterior (AP) radiograph of the cervical spine, the central ray should be centered at the level of the thyroid cartilage, which corresponds to the C4 vertebral level. The thyroid cartilage serves as a palpable landmark and is located at the level where the trachea bifurcates. Positioning the central ray at this location ensures that important structures, including the cervical vertebrae from C3 to C7, as well as the surrounding soft tissue, are well imaged.

Centering at the thyroid cartilage provides optimal visualization of the cervical spine, as well as clear definition of the vertebral alignment. This positioning also helps to minimize distortion and maximize clarity in the resulting radiographic image.

In contrast, centering at other specified vertebral levels such as C4, C6, or C3 may not provide the most accurate representation of the entire cervical spine region. Centering at C6 may omit C3 and C4 from view, while centering too high or too low could lead to important anatomical features being cut off in the radiograph. Thus, centering at the thyroid cartilage is recognized as the standard approach for obtaining a thorough and diagnostic AP view of the cervical spine.