Big rib sign

The big rib sign is a sign to differentiate right and left ribs on lateral chest radiographs.

It exploits a technique of magnification differences on lateral projections between right and left ribs. For example, on right lateral projections the left ribs appear larger than right ribs.

This sign can be useful but may be difficult to appreciate as the difference in size between ribs is ~10% and is not applicable when the posterior ribs are superimposed.