Planning external radiotherapy

Radiotherapy masks and moulds

You might need to have a radiotherapy mask or mould made before you start treatment. They can also be called shells. They keep the treatment area of your body still each time you have your radiotherapy. This is so your treatment is as accurate as possible.

You might need a mask for radiotherapy of your head and neck. Or a mould for your arm or leg, or more rarely for your breast.

You can see through most types of masks or moulds, as they usually have lots of small holes. Your radiographers might make marks on them. They use the marks to accurately line up the radiotherapy machine for each treatment. It is important that you are in exactly the same position each time.

It takes between 10 to 45 minutes to make a mask or mould.

Last reviewed: 30 Oct 2023

Next review due: 30 Oct 2026

What is external radiotherapy?

External radiotherapy uses radiotherapy machines to aim radiation beams at a cancer. This destroys the cancer cells. There are different types of external radiotherapy.

Planning external radiotherapy

Your radiotherapy team carefully work out how much radiation you need to treat the cancer and exactly where you need it.

Where you have radiotherapy

You usually have radiotherapy as an outpatient, which means travelling each day to the radiotherapy department at your nearest cancer centre or unit.

Your cancer type

Search for the cancer type you want to find out about. Each section has detailed information about symptoms, diagnosis, treatment, research and coping with cancer.

Radiotherapy main page

Find out about cancer treatment with radiotherapy, including external radiotherapy, internal radiotherapy, side effects, radiotherapy for symptoms and follow up after treatment.