Why the SID in lateral cervical x-ray is 180cm?

The Source-to-Image Distance (SID) in a lateral cervical x-ray is typically set at 180 cm to minimize distortion and magnification of the cervical spine structures. This longer distance helps to reduce the divergence of x-ray beams, resulting in clearer images with better detail and contrast. Additionally, it allows for improved visualization of the anatomy while maintaining an appropriate level of radiation exposure.