Sinus CT scan

Answer 1

Definition

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).

Alternative Names

CAT scan - sinus; Computed axial tomography scan - sinus; Computed tomography scan - sinus; CT scan - sinus

How the test is performed

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 without stopping.)

A computer creates separate images of the body area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the body area can be created by stacking the 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.

How to prepare for 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 (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.
• Let your doctor know if you have ever had a reaction to contrast. You may need to take medications before the test in order to safely receive this substance.
• Before receiving the contrast, tell your health care provider if you take the Diabetes medication metformin (Glucophage) because you may need to take extra precautions.

If you weigh more than 300 pounds, find out if the CT machine has a weight limit. Too much weight can cause damage to the scanner's working parts.

You will be asked to remove jewelry and wear a hospital gown during the study.

How the test will feel

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.

Why the test is performed

CT rapidly creates detailed pictures of the sinuses. The test may diagnose or detect:

• Birth defects in the sinuses
• Infection in the bones of the sinuses (osteomyelitis)
• Injury to the face over the sinuses
• Masses and tumors, including cancer
• Nasal polyps
• The cause of repeated bloody noses (epistaxis)
• Sinus infection or sinusitis or a sinus infection

This results from this test may also help your health care provider plan for sinus surgery.

Normal Values

Results are considered normal if the sinuses are normal in appearance.

What abnormal results mean

Abnormal results may be due to:

• Birth defects
• Bone fractures
• Cancer
• Polyps in the sinuses
• Sinus infection (sinusitis)

What the risks are

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans do expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. You and your doctor should weigh this risk against the benefits of getting a correct diagnosis for a medical problem.

Some people have Allergies to contrast dye. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.

• The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea or vomiting,sneezing, itching,or hives may occur.
• If you absolutely must be given such contrast, your doctor may give you antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. Those with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.

References

Aygun N, Zinreich SJ. Radiology of the nasal cavity and paranasal sinuses. In: Cummings CW, Flint PW, Haughey BH, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2010:chap 44.

Grainger RG, Thomsen HS, Morcos SK, Koh D, Roditi G. Intravascular contrast media for radiology, CT, and MRI. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 2.

Shaw AS, Dixon AK. Multidetector computed tomography. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 4.

Reviewed By

Review Date: 01/31/2011

Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Jason Levy, MD, Northside Radiology Associates, Atlanta, Georgia. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

Answer 2

Definition

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).

Alternative Names

CAT scan - sinus; Computed axial tomography scan - sinus; Computed tomography scan - sinus

How the test is performed

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.

How to prepare for the test

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.

How the test will feel

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.

Why the test is performed

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

Normal Values

Results are considered normal if the sinuses are normal in appearance.

What abnormal results mean

Abnormal results may be due to:

• Birth defects
• Bone fractures
• Cancer
• Polyps in the sinuses
• Sinus infection (sinusitis)

What the risks are

CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. CT scans do create low levels of ionizing radiation, which has the potential to cause cancer and other defects. However, the risk associated with any individual scan is small. The risk increases as numerous additional studies are performed.

In some cases, a CT scan may still be done if the benefits greatly outweigh the risks. For example, it can be more risky not to have the exam, especially if your health care provider thinks you might have cancer.

The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea or vomiting, sneezing, itching, or hives may occur. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.

If you absolutely must be given such contrast, your doctor may choose to treat you with antihistamines (such as Benadryl) or steroids before the test.

The kidneys help filter the iodine out of the body. Therefore, those with kidney disease or diabetes should receive plenty of fluids after the test, and be closely monitored for kidney problems. If you have diabetes or are on kidney dialysis, talk to your health care provider before the test about your risks.

Before receving the contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage) because you may need to take extra precautions.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.

References

O'Handley JG, Tobin E, Tagge B. Otorhinolaryngology. In: Rakel RE. Textbook of Family Medicine. 7th ed. Philadelphia, Pa:Saunders Elsevier; 2007:chap 25.

Rosenfeld RM, Andes D, Bhattacharyya N, Cheung D, Eisenberg S, Ganiats TG, et al. Clinical practice guideline: adult sinusitis. Otolaryngol Head Neck Surg. 2007;137:S1-S31.

Hulett KJ, Stankiewicz JA. Primary sinus surgery. In: Cummings CW, Flint PW, Haughey BH, et al. Otolaryngology:Head and Neck Surgery. 4th ed. Philadelphia, Pa: Mosby Elsevier;2005:chap 53.

Answer 3

No, a CT scan is a very quick and painless scan. Generally sinus scans are done to show blockages or the extent of fluid build up in the sinuses.