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Planning radiotherapy

Radiotherapy means the use of radiation, usually x-rays, to destroy cancer cells. You might have external radiotherapy as part of your treatment for ALL. External radiotherapy uses a machine outside the body to aim radiation beams at the cancer.

Before you start treatment, your radiotherapy team has to carefully plan it. This means working out how much radiation you need and exactly where you need it. You have a planning appointment, which takes from 15 minutes to 2 hours.

You have a CT scan in the radiotherapy department to help with planning.

Photo of a CT scanner

Your radiographers tell you what is going to happen. They help you into position on the scan couch. You might have a type of firm cushion called a vacbag to help you keep still.

The CT scanner couch is the same type of bed that you lie on for your treatment sessions. You need to lie very still. Tell your radiographers if you aren't comfortable.

Injection of dye

You might need an injection of contrast into a vein in your hand. This is a dye that helps body tissues show up more clearly on the scan.

Before you have the contrast, your radiographer asks you about any medical conditions or allergies. Some people are allergic to the contrast.

Having the scan

Once you are in position your radiographers put some markers on your skin. They move the couch up and through the scanner. They then leave the room and the scan starts.

The scan takes about 5 minutes. You won't feel anything. Your radiographers can see and hear you from the CT control area where they operate the scanner. 

If you are going to have radiotherapy to the brain or top or your spinal cord, your radiographer or a technician might make a mask for you before you have the planning CT scan. The mask is to help keep you still and in the correct position during your treatment.

Radiotherapy treatment mask (shell)

Your radiographer or technician makes your mask in the radiotherapy department. They might call the mask a radiotherapy shell.

The mask covers your face, and the top and sides of your head. It attaches to the couch when you are lying down for the planning scan or radiotherapy treatment.

The process of making the mask can vary slightly between hospitals. It usually takes around 30 minutes.

Before making the mask

You need to wear clothes that you can easily take off from your neck and chest. You also need to take off any jewellery from that area.

Facial hair, long hair or dreadlocks can make it difficult to mould the mask. Your radiotherapy team will tell you if you need to shave or tie your hair back.

Making the mask

The technician uses a special kind of plastic that they heat in warm water. This makes it soft and pliable. They put the plastic on to your face so that it moulds exactly. It feels a little like a warm flannel and is a mesh with holes in so you can breathe.

After a few minutes the mesh gets hard. The technician takes the mask off and it cools down. You might need to have one more fitting to make sure it is exactly right.

You wear the mask for your planning CT scan. Your radiotherapy team keep the mask in the department for when you go back for treatment. You wear it for each treatment session.

Photograph of a stereotactic radiotherapy mask for treating brain, head and neck cancers

Radiotherapy planning for TBI

You might have radiotherapy as part of a stem cell transplant. In this case you have radiotherapy to your whole body. This is called total body irradiation (TBI).

First you have a planning session of about an hour to create the treatment plan. You usually lie on your back on the couch. You might have your arms across your chest or resting on your lower tummy (abdomen). Your radiographers will put support pads (cushions) under your knees and you might also have supportive pads around your body to keep you in position.

Your radiographers take several measurements and then you have a CT scan. They will make two very small permanent dots on both sides of your hips. They use these marks to help put you in the correct position when you have your treatment.

During this session you might have a very small dose of radiotherapy. This is to help with the planning. You have no side effects from this.

After your planning session

Your radiographer will tell you when to go back for your treatment sessions. It takes at least a few days for your radiotherapy team to create your radiotherapy plan.

Last reviewed: 
01 Aug 2018
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    Annals of Oncology, 2016. Volume 27, Supplement 5, Pages 69-82

  • Practical Radiotherapy Planning (4th Edition)
    A Barrett and others
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  • Practical Radiotherapy and Chemotherapy Planning
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    S Faithfull and M Wells
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  • Whole body radiotherapy: A TBI-guideline
    U Quast
    Journal of Medical Physics, 2006. Volume 31, Issue 1, Pages 5-12

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in if you need additional references for this information.

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