X-rays can be used to examine almost all areas of the body, from the teeth and their roots to the spine and to the inner organs. Sometimes substances called contrast agents are used to aid in highlighting certain areas of the body. For example, barium contrast agent can be ingested before an x-ray of the upper digestive tract is taken to highlight these organs in further detail when investigating reasons for difficulty swallowing. It is essential that the patient stay as still as possible during an x-ray and often will have to be placed in certain positions so that the x-ray machine can be pointed to the area of interest. For this reason, most x-rays are taken with the patient under sedation or general anesthetic.