The disappearing ellipse: a new sign of a linear skull fracture.
A linear nondepressed skull fracture may be seen as two connecting lines because slight angulation of the beam of radiation results in separate visualization of the fracture as it crosses the outer table and then the inner table. These two lucent lines form an elliptical shape. A second projection can result in superimposition of the inner and outer table fractures, and the elliptical configuration is no longer seen. This disappearing ellipse is offered as an additional sign of a linear skull fracture which can help differentiate such fractures from vascular grooves.
D003937:Diagnosis, Differential; D006801:Humans; D011859:Radiography; D012887:Skull Fractures / Q000000981:diagnostic imaging*