Intrathoracic rib: CT features.

Computed tomography may suggest the diagnosis of intrathoracic rib (IR) by two criteria: (a) The abnormal extrapleural shadow has cortical margins on bone windows; (b) the shadow articulates with the spine or with a rib. The significance of an IR lies in recognizing it as an innocuous thoracic shadow, one not to be mistaken for other more serious lesions, thus preventing additional procedures.