Rotation and tilt are two of the most common positioning errors.

 A. Rotation occurs when the median Saggital plane is not parallel to the film.

Model Skull radiographs Lateral &  PA Rotated

  B. Tilt occurs when the interpupilary line is not at 90 to the film.

Causes of Positioning Errors

When positioning a patient's head, it is necessary to look at various facial features and palpate various anatomical landmarks in order to place certain planes precisely in relation to the film plane. Although the human body is supposed to be symmetrical this is not always true.

The ears nose and jaw being the notable exceptions. Bony parts such as the mastoid tips and the orbital margins are usually more accurate landmarks, for example whilst positioning it is often more accurate to use the eyes rather than the nose as positioning aids.

 The third and forth errors in skull radiography are combinations of incorrect centering and central ray angulation, usually an error in the relationship to the central ray to a baseline angle