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Planning radiotherapy

The radiotherapy team plans your external beam radiotherapy before you start treatment. This means working out how much radiation you need to treat the cancer and exactly where you need it. Your planning appointment takes from 30 minutes to a few hours.

You usually have a planning CT scan in the radiotherapy department.

The scan shows the cancer and the area around it. You might have other types of scans or x-rays to help your treatment team plan your radiotherapy. The plan they create is just for you.

Photo of a CT scanner

Before the scan

You change out of your clothes and put on a hospital gown. When you’re ready the radiographers help you into position on the scan couch. They tell you what is going to happen. 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 the radiographers if you aren't comfortable.

Once you're in position the radiographers make a radiotherapy mould (shell) of your face.

Radiotherapy mould (shell)

Your treatment team might make a mould (shell) for you.

You wear it during the treatment sessions to keep you very still. The radiographers may also make marks on it. They use the marks to line up the radiotherapy machine for each treatment.

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

Before making the shell

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 shell. The radiotherapy staff will tell you if you need to shave or to tie your hair back.

Making the shell

A 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, neck and chest so that it moulds exactly. 

After a few minutes the plastic gets hard. The technician takes the shell off and it is ready to use.

Radiotherapy mask

During the scan

When the shell has been made the radiographers put some markers on the shell and 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. The radiographers can see you from the CT control area where they operate the scanner. 

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 medium, the radiographer asks you about any medical conditions or allergies. Some people are allergic to the dye.

After the scan

The radiographers make pin point sized tattoo marks on your skin. They use these marks to line you up into the same position every day. The tattoos make sure they treat exactly the same area for all of your treatments. They may also draw marks around the tattoos with a permanent ink pen, so that they are clear to see when the lights are low.

Radiotherapy tattoo marks
Radiotherapy treatment area marks.

The radiotherapy staff tell you how to look after the markings. The pen marks might start to rub off in time, but the tattoos won’t. Tell your radiographer if that happens. Don't try to redraw them yourself. 

The radiographers will then help you off the CT scanner couch and you can get changed back into your clothes. You stay in the department for about 15 to 30 minutes if you had an injection of the dye. This is in case it makes you feel unwell, which is rare.

You should be able to go home or back to work. You can eat and drink normally.

Possible risks

A CT scan is safe for most people but there are some possible risks. Your doctor and radiographer make sure the benefits of having the scan outweigh these risks.

Allergic reaction

Rarely, people have an allergic reaction to the contrast medium. This most often starts with weakness, sweating and difficulty breathing. Tell your radiographer immediately if you feel unwell so they can give you medicine.

Contrast medium

There is a risk that the contrast medium will leak outside the vein. This can cause swelling and pain in your arm but it’s rare.

Radiation

Exposure to radiation during a CT scan can slightly increase your risk of developing cancer in the future. Talk to your doctor if this worries you.

Pregnancy

Pregnant women should only have CT scans in emergencies. Contact the department as soon as you can before the scan if you are pregnant or think that you might be.

After your planning session

It can take a few days or up to 3 weeks before you start treatment.

Your radiographers and doctors create your radiotherapy plan. They make sure that the area of the cancer will receive a high dose and nearby areas receive a low dose. This reduces the side effects you might get during and after treatment. 

Last reviewed: 
11 Jul 2018
  • National Radiotherapy Implementation Group Report - Image Guided Radiotherapy (IGRT) guidance for implementation and use

    National Cancer Action Team, August 2012

  • Radiotherapy Services in England 2012

    Department of Health Cancer Policy Team, November 2012

  • Advances in radiotherapy

    S Ahmed and others. British Medical Journal, 2012. Vol. 345

  • External Beam Therapy
    P Hoskin
    Oxford University Press, 2012

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