Planning the treatment

Treatment needs to be carefully planned to ensure that enough radiation reaches the cancer, while as little as possible reaches healthy tissues and organs. The planning steps below may occur over a few appointments.

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Initial appointment and examination

This may take up to two hours. Your radiation oncologist will assess whether radiation therapy is the right treatment for you. This will involve talking to you, doing a physical examination, and looking at all your tests and scans.

The benefits and side effects of radiation therapy and what to expect during planning and treatment will be explained. You might also meet the radiation oncology nurse and a radiation therapist who can give you more information.

The radiation oncologist may arrange further x-rays, scans or other tests to find out more about the cancer.

You may want to take someone with you to keep you company, ask questions and make notes.


Masks and casts

In most cases, you will need some type of device to ensure you are in the same position for each session and to help keep you still during treatment. This is known as an immobilisation device or cast and it will be custom-made to fit you. Depending on the area being treated, the device could be a mask, head rest, breast board, or a knee or foot cushion.

For radiation therapy to the head or neck, you may need to wear a plastic mask. This can feel strange and confining, but you will still be able to hear, speak and breathe. Tell the radiation therapists if you feel anxious or claustrophobic before or during treatment. They can suggest breathing or relaxation exercises, or arrange for you to have a mild sedative.


Skin markings

To ensure you are positioned in the same way for each treatment session, a few very small permanent ink spots (tattoos) may be marked on your skin. These tattoos are the size of a small freckle and can’t be easily seen.

Sometimes temporary ink marks are made on the skin. Ask the radiation therapist if you can wash these off or if you need to keep them until the full course of treatment is finished. The ink can be redrawn during the course of treatment, but it will gradually fade.

If you have to wear a mask or cast, the markings may be made on this rather than on your skin.

For image-guided radiation therapy, you may have a small surgical procedure to insert markers (usually gold grains) into the cancer. These internal markers can then be seen on scans during the treatment.


Planning CT scan

You will need to have a planning CT scan even if you have already had a CT scan to diagnose the cancer. This step is known as CT planning or simulation.

For this scan, you will be placed in the same position on the table that you will be in for treatment. If you have a mask or cast, you will use it during the scan. The images from the CT scanner will build up a three-dimensional picture of your body. This will show the exact location that needs to receive the radiation.

The radiation therapists will send the images from the scans to a computer. This allows the radiation oncologist to outline exactly where they need to treat. The oncologist will prescribe the appropriate dose of radiation therapy, which will help the medical physicist and therapists to precisely plan your treatment.


This information will apply in most cases, but you may find that things are done slightly differently where you have treatment. Watch this video to learn more about the radiation therapy process.

This information was last reviewed in December 2017
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