A contrast dye may be injected into a vein before the test.

You lie on a table that can be moved by the technician who is operating the scanner. Only your head is positioned inside the CT scanner. The exam usually lasts no more than a few minutes.

You may be allowed to rest your head on a pillow, but this must be done before the scan begins. It is very important that once your head is in place, you do not move it during the test.

You must sign an informed consent form. Remove dentures, any jewelry, and anything metal.

The most discomfort is from the need to lie still on the table during the scan. The scan itself is painless.

You may feel discomfort or burning if you receive contrast dye.

This test is helpful for diagnosing a lesion or other diseases that affect tissues in the following areas:

• Blood vessels
• Eye muscles
• Eyes
• Nerves supplying the eyes (optic nerves)
• Sinuses

Subtle fractures of the eye sockets may also be detected.

• Bleeding
• Graves disease
• Lesions
• Tumor

The amount of radiation in a CT scan is minimal. There may be some concern for nursing or pregnant women. However, the benefits of the scan generally outweigh any risk to the fetus or newborn.

The contrast dye may cause serious allergic reactions in some patients. These reactions may include headache, nausea, and vomiting.