The lateral neck is suggestive of epiglottitis and shows thumbprint and vallecula sign.

The thumbprint sign is due to swollen epiglottis.

The vallecula sign or V sign is due to obliteration of the vallecular space. Vallecula is the preepiglottic space found at the level of hyoid bone, just anterior to the epiglottis. It is occupied by pocket of air, well delineated with the air column parallel to the pharyngotracheal air column. The vallecular sign is present when, instead of a deep linear space, a shallow V shaped space is seen.

Epiglottitis is a clinical diagnosis and under no circumstances, an unstable patient should be made to lie flat to obtain an x-ray which may close off the airway.

Reference: can be found here