Planning radiotherapy

The radiotherapy team plan your external radiotherapy before you start treatment. This means working out the dose of radiotherapy you need and exactly where you need it.

Your planning appointment takes from 15 minutes to 2 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 your planning starts, your radiographer asks you to sign a consent form. If you're a woman they check with you that you’re not pregnant and remind you not to get pregnant during treatment. This is because radiation can damage an unborn baby.

Your planning appointment

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. 

Ink and tattoo marks

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.

Photograph of radiotherapy tattoo 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. 

Radiotherapy mould to keep a part of the body still

You might have a radiotherapy mould made to fit over a part of your body. The aim of the mould is to keep that part of your body still. This makes sure that the radiotherapy is directed at exactly the same area every time you go for treatment.

For example, you might have a mask or mould to keep your head still if your melanoma is on your head or neck area. Or you might need a mould to keep an arm or leg still if you are having treatment to one of these areas. 

Your radiotherapy team will explain how this is done if this applies to you.

After your planning session

You might have to wait a few days or up to 3 weeks before you start treatment.

During this time the physicists and your radiographer doctor (clinical oncologist) decide the final details of 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: 
30 Apr 2020
Next review due: 
28 Apr 2023
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    The Royal College of Radiologists, 2014.

  • Radiotherapy for skin cancer
    British Association of Dermatologists, 2010 (updated 2016)

  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2015

  • Cancer: Principles and Practice of Oncology (10th edition)
    VT De Vita and others
    Lippincott, Williams and Wilkins, 2015

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