A computed tomography (CT) scan of the orbit is an imaging method. It uses x-rays to create detailed pictures of the eye sockets (orbits), eyes and surrounding bones.
You will be asked to lie on a narrow table that slides into the center of the CT scanner. Only your head is placed inside the CT scanner.
You may be allowed to rest your head on a pillow.
Once you are inside the scanner, the machine's x-ray beam rotates around you but you won't see the x-ray.
A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. The computer can create three-dimensional models of the body area by stacking the slices together.
You must lie still during the exam, because movement causes blurred images. You may be asked to hold your breath for short periods.
The actual scan takes about 30 seconds. The entire process takes about 15 minutes.
Before the test:
Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast helps certain areas show up better on the x-rays. Contrast can be given through a vein (intravenous- IV) in your hand or forearm.
Before the scan using contrast, it is important to know the following:
Some people may have discomfort from lying on the hard table.
Contrast given through an IV may cause a slight burning sensation. You may also have a metallic taste in the mouth and a warm flushing of the body. These sensations are normal and most often go away within a few seconds.
This test is helpful for diagnosing diseases that affect the following areas around the eyes:
An orbit CT scan may also be used to detect:
Abnormal results may mean:
CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. The risk associated with any individual scan is very low. The risk increases as more studies are done.
CT scans are done when the benefits greatly outweigh the risks. For example, it can be more risky not to have the exam, especially if your provider thinks you might have cancer.
The most common type of contrast given into a vein contains iodine.
The kidneys help filter the iodine out of the body. If you have kidney disease or diabetes, you should be closely monitored for kidney problems after contrast is given. If you have diabetes or have kidney disease, talk to your provider before the test to know your risks.
Before receiving the contrast, tell your provider if you take the diabetes medicine metformin (Glucophage) because you may need to take extra precautions. You may need to stop the medicine for 48 hours after the test.
In rare cases, the dye can cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, tell the scanner operator right away. Scanners come with an intercom and speakers, so the operator can hear you at all times.
Reviewed By: Jason Levy, MD, Northside Radiology Associates, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.