An X-ray of the Mastoid is a safe and painless test to visualise the mastoid, a bone of the skull, located just behind the ear. The indications of this test are to diagnose the infection of the air spaces of mastoid (mastoiditis), to diagnose any suspected conditions like otitis media (infection of the ear) and cholesteatoma (abnormal skin growth in the middle ear behind the eardrum), to look for any suspected injury or fracture of the mastoid bones and for the diagnosis of any suspected abnormal growth (tumor) in the mastoid bone region.