What is a radiotherapy mask?

For most types of radiotherapy to your brain, head or neck area, you wear a radiotherapy mask during each treatment. This is sometimes also called a mould, head shell or cast.

The mask is made to hold your head and neck still and in exactly the right position. This helps make your treatment as accurate and effective as possible. The mask fits tightly but should not be uncomfortable. You can breathe normally while you are wearing it.

Before the radiotherapy mask is made

There are some things you may be asked to do before your mask is made, to help make sure your mask fits well:

Dental work

Before the radiotherapy mask is made, you may need to see a dentist to have your mouth and teeth checked. If some of your teeth are unhealthy, they may need to be removed or repaired.

Dental work can change the shape of your mouth and face slightly. So, it is important this is done before the mask is made.

Mouth bites

Some people are given a mouth bite to wear inside their mouth during radiotherapy. This holds your mouth and jaw in position, so the right area is treated. This can also help reduce side effects.

Your radiotherapy team will tell you if you need a mouth bite. If you do, you also need to wear it while your mask is made.


You do not usually need to have your hair cut before the mask is made. But if you have a beard, you should trim or shave it off. During your treatment, do not make big changes to your hairstyle or let your facial hair grow back. This can affect how well the mask fits.

Wet shaving can irritate the skin during radiotherapy. Use an electric shaver if you need to shave.

How a radiotherapy mask is made

A technician or radiographer usually makes the mask in the radiotherapy department. How the mask is made can be different depending on the hospital. It usually takes about 30 minutes.

You may need to take off some of your clothes and wear a hospital gown while it is being made. If you wear glasses, have dentures or usually wear a wig or head scarf, you will be asked to remove these too.

Masks are usually made using a type of mesh plastic called thermoplastic. It becomes soft when heated in hot water. This is moulded to fit the shape of your head and neck.

Less often, wet plaster bandages are used to make a mould. This mould is then used to make a mask out of a type of clear plastic called Perspex®.

Making a mesh plastic mask

Stage 1

You lie on a couch, similar to the one used for treatment. Your head rests on a plastic head rest. The technician or radiographer tries to make you as comfortable as possible. They warm the plastic mesh and put it onto your face. It gently moulds to fit your head and neck.

This feels a bit like a hot flannel. It will not harm you and it cools down very quickly. The plastic mesh has lots of holes in it, so you can breathe easily.

The first photo below shows the plastic mesh being placed onto someone’s face. The second photo shows the mesh being gently moulded to their face and around the sides and top of their head.

Preparing a radiotherapy mask - stage 1
Image: Preparing a radiotherapy mask - stage 1
Preparing a radiotherapy mask - stage 1b
Image: Preparing a radiotherapy mask - stage 1b

Stage 2

You lie still for up to 15 minutes while the plastic mesh cools down and hardens.


Preparing a radiotherapy mask - Stage 2
Image: Preparing a radiotherapy mask - stage 2


Stage 3

The technician or radiographer takes the mask off. It is now ready to be used.

The first photo below shows the mask being lifted off someone’s face. The second photo shows the person with their finished mask.


Preparing a radiotherapy mask - stage 3a
Image: Preparing a radiotherapy mask - stage 3a



Preparing a person for a radiotherapy mask- 3b
Image: Preparing a person for a radiotherapy mask- 3b


Making a Perspex® mask

A Perspex® mask is made in 2 stages. First, the technician or radiographer makes a plaster mould of your head and neck. Then they use the mould to make the clear plastic Perspex® mask for your treatment.

To make the plaster mould, they spread a cool cream or gel on your face to protect your skin. They also give you a swimming cap or other covering to protect your hair from the plaster mould mixture. They then put wet strips of plaster of Paris bandage on top. They leave holes around your nose and mouth, so you can breathe easily.

Plaster of Paris gets warm as it sets. This is normal and does not harm your skin, but it may feel uncomfortable. It takes about 5 minutes to set and then the mould is taken off.

They then make a Perspex® mask from the mould.

Radiotherapy masks and treatment planning

Once the mask is ready, your treatment can be planned. This may be straight after the mask is made, or you may need to come back for another appointment.

Treatment planning makes sure the radiotherapy is aimed precisely at the cancer.

The treatment planning appointment usually takes 30 to 60 minutes. You do not need to wear the mask for the whole time.

The radiotherapy team help you get into the same position as when your mask was made. The mask is gently placed over your face and fixed to the treatment couch, so your head and neck do not move. The mask should be tight but not uncomfortable. If it is uncomfortable, tell the staff so that they can try to adjust it.

Radiotherapy skin markings

During treatment planning, the doctor or radiographer may make a few marks on the mask. You may also have markings made on your chest. These help the radiographers position you for treatment.

These markings are made the same way as a tattoo. The marks are the size of a pinpoint and are only made with your permission. It can be a little uncomfortable while they are being made, but it makes sure that the treatment is directed accurately.

If you are concerned about having permanent marks or already have a tattoo in the treatment area, let your radiographers know. They can discuss other options with you.

Wearing the radiotherapy mask for treatment

When you have the radiotherapy treatment, you lie in exactly the same position on a couch below a radiotherapy machine. The radiographer will gently place the mask over your head and neck and fix it to the couch.

Treatment can take 10 to 30 minutes. It is not painful. The team can see, hear and talk to you and are close by if you need them at any time.

Support during treatment

You may feel very nervous about wearing the mask, or feel claustrophobic. If you want to, you can bring some calming music or a relaxation podcast to listen to during your appointments.

Most people cope well with the support of the radiotherapy team. Tell your team if you are uncomfortable, so they can help you. Your doctor can give you medication to take before your treatment to help you relax. But this is not usually needed.

Getting support

Macmillan is here to support you. If you would like to talk, you can do the following:

About our information

  • References

    Below is a sample of the sources used in our radiotherapy information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    The Leeds teaching hospitals NHS Trust. Having a radiotherapy mask made. Information for patients. Available from flipbooks.leedsth.nhs.uk/LN000001.pdf (accessed October 2021).

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr David Gilligan, Consultant Clinical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 August 2022
Next review: 01 August 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.