Final answer:
If T1 is not demonstrated on the C-spine lateral, an additional projection called a swimmer's view can be performed to visualize the T1 vertebra.
Step-by-step explanation:
If T1 is not demonstrated on the C-spine lateral, an additional projection called a swimmer's view can be performed to visualize the T1 vertebra. The swimmer's view is a modified anteroposterior projection where the patient's shoulders are rolled forward, allowing for better visualization of the T1 vertebra. This view is useful when T1 is obscured by the superimposition of the clavicles and upper thoracic vertebrae in the standard lateral view.