What is a CT scan?

A computed tomography (CT) scan is an x-ray test that takes a series of detailed pictures of the organs inside your body. Each picture is of an area, or 'slice' of the body, similar to the slices of a loaf of bread.

When is a CT scan used?

CT scanning is used when your doctor needs more detailed information than can be provided by a physical examination or regular x-rays. One of the main roles is to reveal tumors, particularly those which are small. It is also good for detecting complications of surgery, causes of chest or abdominal pain and extent of internal injury following trauma.

CT scans can be done so that the radiologist can view your internal anatomy in three dimensions (3D). Surgeons sometimes find this type of 3D information useful in planning a surgery.

How do I prepare for a CT scan?

Allergies

• Tell your doctor if you have an allergy to IV contrast/ dye, shellfish or iodine.
• You may get a prescription for Prednisone to start taking 24 hours before your scan, or a different type of test may be ordered.
• If you arrive for your scan without taking the Prednisone, your CT scan will likely need to be rescheduled.

Bloodwork

• Ask your doctor if your blood work was ordered.
• Most everyone needs a creatinine level drawn within two weeks before their CT scan. If the blood test is not done, your CT scan will be delayed until it is done.
• If you had recent chemotherapy, you will need a creatinine test after your last treatment.
• If your blood is drawn in your local area, please bring a copy of the results with you on the day of your CT scan or have the results faxed to the CT department at 919-681-7131.
• If you take a medicine called Metformin (Glucophage®), you will need to call your family physician to get blood work done to check your creatinine level after the CT, and before restarting Glucophage®.

Eating and Drinking

• You may eat light food prior to your CT scan (e.g., juice, toast, soup).
• If you will be receiving oral contrast, please do not eat for an hour before the procedure.
• You may want to limit the amount of fluids you drink just before the CT scan to avoid interrupting the procedure to use the bathroom.

Medicines

• Take your medicines as usual, except if you are taking a medicine called Metformin (Glucophage®). If you are a diabetic on the medicine and will be receiving IV contrast, you will be asked to stop the medicine the day of the CT scan and for 48 hours after the CT scan, and until your creatinine level is checked with a blood test.

Contrast

• Contrast is sometimes used to help the CT show certain parts of the body better.
• Oral contrast (taken by mouth) is used to better see the stomach and other parts of the gastrointestinal (GI) tract.
  • Types of oral contrast include:
    • Gastrografin® - mix with cola or juice
    • Readi-Cat® - milkshake-type liquid, must be used if allergic to iodine
  • Do not drink oral contrast if you are having a CT scan because you are donating a kidney or liver.
  • The clinic staff will give you the oral contrast when the CT is scheduled. If they do not, please ask about it.
  • Start drinking your oral contrast one hour before your scheduled CT scan. Try to drink the entire amount within 30 minutes.
  • If you are having a CT scan of your abdomen or pelvis, and did not get your oral contrast from the clinic:
    • Please arrive in the CT department one hour before your appointment time
    • Tell the receptionist that you came early to drink your contrast
    • All of the oral contrast needs to be in your body at least one hour before the CT scan can be started.
• IV - Intravenous (IV) contrast is used to better see non-GI tissues, such as tissues of the brain, spine, prostate, bladder, and kidneys

If you think you may be pregnant

• Notify your doctor, nurse, or CT technologist immediately. X-rays can be dangerous to a fetus.

What happens during the procedure?

CT scanning can be done either in Duke University Hospital or Duke Clinic radiology departments. Be sure you know where you are scheduled for the test.

For many types of CT scans, an IV line will be started in your arm by a nurse so that you can receive intravenous contrast material or x-ray dye. If you have had lymph nodes removed under your arm, please tell the nurse so your IV can be started on the opposite side.

You will then be asked to lie flat on a table, which slowly moves you in and out of the scanner. The hole through which you will slide is quite large on present day scanners; therefore, claustrophobia is rarely a problem.

If you are having a CT of the chest or abdomen, you will be asked to hold your breath for up to 30 seconds. The technologist can help you with longer breath holds by giving you some supplemental oxygen or some special breathing maneuvers. If IV contrast is used, it will be given as scanning is started. You may experience a sensation of warmth in your chest and abdomen and perhaps a metallic taste in your mouth during the contrast administration. These symptoms are normal and will subside. If you experience any other symptoms such as nausea, itching, sneezing, shortness of breath or chest discomfort, please alert the nurse immediately. Furthermore, if you feel any pain at the injection site in your arm, alert the nurse immediately.

Expect to be in the Radiology - CT department for one to two hours. Overall, the entire CT scan should require less than five minutes to complete and you should be on the table less than 15 minutes.

What happens after the procedure?

In general, there are no special measures to be taken after the procedure. If you received oral or IV contrast, drink plenty of liquids (64 ounces/8 cups) over the rest of the day to flush the contrast out of your body.

While it is not absolutely necessary to have someone with you when you are scanned as an outpatient, it may be helpful. If you develop an adverse reaction that requires treatment, you may receive diphenhydramine (Benadryl®) which causes drowsiness, and could prevent you from driving yourself home.

What are the risks associated with this procedure?

CT scanning does use x-rays and it would be considered unhealthy if you were exposed in this fashion on a frequent basis (every few days). X-ray exposure is an important consideration particularly in children, young adults and pregnant females (especially in the first three to four months of pregnancy). It is important to note that the amount of radiation received during one or even several CT scans is not considered harmful.

There is a small risk that you may have an allergic reaction to the intravenous contrast material. Rarely, patients are allergic to the oral contrast material. If you have had a reaction to the contrast material from a prior examination (e.g., angiogram, CT scan, or IVP) please alert the nurse or the technologist immediately. Furthermore, please inform the nurse of all your allergies.

When should I call my doctor?

Call your doctor immediately if you experience

• Any worsening of pain or symptoms
• Allergy-type symptoms (rash, itching, sneezing, hives, etc.) during the two days following the CT scan.

How will I find out the results?

• A radiologist will read your CT scan and send a report to the doctor who ordered your scan. Your doctor or his/her staff will provide the results over the phone or during an appointment.

Who can I call for questions or concerns?

• CT Scheduling: 919-684-7268
• CT Coordinator: 919-684-7221
• CT Chief Technologist: Donna D. Parker, RT(R) CT: 919-684-7352

This article is intended as a resource for patients receiving their cancer care at Duke University Hospital or Duke Clinic. It is not intended to substitute for medical advice from your health care team. If your doctor’s instructions differ from the information in this article, please talk with your doctor before making any changes.