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. This bone is made of air containing spaces and cells that helps to drain and clean the ear. The image is recorded on a special X-ray film. The X-ray image is black and white. Dense structures such as the bones, appear white and softer body tissues, such as the skin and muscles appear darker. The actual exposure time to radiation is usually less than a second, although the overall test may take 15-20 minutes.