HF 8041

CT (CAT) Scan for Radiation Treatment Planning for the Brain, Head or Neck

This handout explains what you can expect during your CT scan. When you get to the Radiation Oncology department please check in at the front desk.

A CT scan is a type of x-ray. While some CT scans are done to diagnose disease, the purpose if this scan is to plan your radiation treatments. Your doctor may or may not be there during the scan, but you will meet a radiation therapist. This may be the same person you see at your radiation treatments.

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We will review your health records before your CT scan. If you are pregnant, or think you might be pregnant, please tell us before the scan. Your doctor may order a pregnancy test if you are of childbearing age.


To help us get a better picture, we may need to use intravenous (IV) contrast. If we do have to use contrast:

  • An IV is placed in your arm and left there until the scan is done.

  • You may need a blood test.

  • Wear clothes with loose sleeves.

IV contrast is a clear liquid that we give through your IV during the scan. As it goes through your blood, it gives us a better picture of your blood vessels and organs. Some patients say that they feel warm or have a strange taste in their mouth when getting contrast. These are normal side effects that should only last a few seconds.

If you have an allergy to the CT contrast or are allergic to shellfish or iodine products, please let your doctor or nurse know.

If you have contrast during your scan and take certain oral medicines for your diabetes, please let your nurse or doctor know.

If you take Glucovance®, metformin, Metaglip®, Avandamet® or Glucophage® please let us know. In some cases, this medicine needs to be held 48 hours after injection. The radiation oncology nurse will tell you if you need to stop the medicine and when it can be started again. We may need to find a short-term plan to manage your blood sugars until you can restart this medicine. This may involve talking to your primary doctor. If you do not need the CT contrast, you do not need any changes in your medicines.

During Your Scan

The entire visit will take about 30 minutes. The scan itself takes only a few seconds.

Remove any earrings, necklaces, glasses, dentures or hearing aids before the scan.

When we are ready, you will lay on a narrow table, with your head resting on a cushion. We will gently press the cushion around your head and neck until it begins to harden.

Your doctor may also want to use a small mouthpiece for you to rest your teeth on. Once this is done, a mask will be made.

The mask takes about 10-15 minutes to make. The mask is a flexible, mesh plastic that is placed in warm water. The mask will cover your head and face and may extend to your shoulders. You can see and breathe through the mask. The mask will feel warm and wet, like a wet washcloth. As it hardens you will feel the mask tighten. It will not hurt, but you may notice it.


The CT scan is done right after the mask is made. The table will move you in and out of the scanner several times. During the scan, you are alone in the room but we can see and hear you at all times. You must lie still during the scan. If you need something, or have any problems during the scan, just speak up. We can hear you.

After Your Scan

The mask will be removed once it feels cool and hard. The mask and any mouthpieces are kept for your daily radiation treatments. If you had an IV, this may be removed now. You need to drink extra fluids over the next 24 hours to help flush the contrast out of your body. If you have problems taking fluids, please let us know.

Once the scan is done, it will be sent to your doctor. These images are used to plan your radiation treatments. This will take a few days.

The radiation therapists will schedule your radiation treatments. Unless you and your doctor have made other plans, they will call you with your schedule within 5-10 business days. They will give you instructions on where to go and how to prepare for your treatments.

When to Call

Please call if you have any questions or concerns.
Radiation Oncology Clinic:
(608) 263-8500.
Toll free: 1-800-323-8942.

If the clinic is closed, your call will be transferred to our answering service. Ask to speak to the radiation doctor on call. The doctor will call you back.

If you are a patient receiving care at UnityPoint – Meriter, Swedish American or a health system outside of UW Health, please use the phone numbers provided in your discharge instructions for any questions or concerns.