How should the central ray be directed when using the open-mouth position for imaging the atlas and axis?

In the open-mouth position for imaging the atlas and axis (the first two cervical vertebrae), the central ray must be directed parallel to the line drawn from the lower edge of the upper incisors to the base of the occiput. This positioning is crucial because it allows for optimal visualization of the C1 and C2 vertebrae without superimposition from the structures of the mandible or the skull.

When the central ray is aligned in this manner, it ensures that the anatomic alignment is captured effectively, facilitating accurate diagnosis and assessment. Proper angling in relation to both the upper incisors and the base of the occiput is also essential to account for the natural curvature and orientation of the cervical spine.

While other options may suggest different orientations, they do not align with the standard practice essential for a clear and diagnostic image in this specific projection.