A computed tomography (CT) scan of the sinus is an imaging test that uses x-rays to create detailed pictures of the air-filled spaces inside the face (sinuses).

CT rapidly creates detailed pictures of the sinuses. The test may be used to:

• Diagnose an infection in the bones of the sinuses (osteomyelitis)
• Diagnose birth defects in the sinuses
• Diagnose sinusitis or a sinus infection -- if your infection does not improve with antibiotics, you have had many infections, or your sinus symptoms never completely go away
• Evaluate injury or trauma to the face over the sinuses
• Find nasal polyps
• Help the health care provider plan for sinus surgery
• Identify the cause of repeated bloody noses (epistaxis)
• Look for cancerous or non-cancerous tumors

You will be asked to lie on a narrow table that slides into the center of the CT scanner. You may lie on your back, or you may lie face-down with your chin raised.

Once you are inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam in one continuous motion.)

Small detectors inside the scanner measure the amount of x-rays that make it through the sinuses. A computer takes this information and uses it to create several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the sinuses can be created by stacking the individual slices together.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time. Straps and pillows may be used to keep you still during the procedure.

The actual scan should take about 5 minutes. The entire process should take 15 minutes.

Avoid doing a nasal wash within 24 hours before the test is performed.

Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast can highlight specific areas inside the body, which creates a clearer image.

Some people have allergies to IV contrast and may need to take medications before their test in order to safely receive this substance.

Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, you may also be asked not to eat or drink anything for 4-6 hours before the test.

If you weigh more than 300 pounds, have your doctor contact the scanner operator before the exam. CT scanners have a weight limit. Too much weight can cause damage to the scanner's working parts.

Since x-rays have difficulty passing through metal, you will be asked to remove jewelry and wear a hospital gown during the study.

Some people may have discomfort from lying on the hard table.

Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.