Radiation Therapy Thermoplastic Mask

Author: Courtney Misher, MPH, BS R.T.(T)
Last Reviewed: October 03, 2022

Radiation therapy thermoplastic mask used for daily treatment.

If your treatment plan includes radiation therapy to your head & neck or brain, then you will likely have to get a thermoplastic mask made for your treatment. Thermoplastic masks are made of a plastic material that looks like mesh.

The mask helps you stay still to ensure accurate delivery of the radiation beam. The mask will be made at the time of the CT simulation. It will be worn every day for treatment. You can communicate with the therapists using your hands while you have the mask on. You can give a thumbs up or thumbs down to answer simple questions that the therapists may ask. If you need the therapists during treatment, raise or wave your hand and they will come into the treatment room to check on you.

What personal items need to be removed before making the mask?

You will be asked to take off any items that are in the treatment area that can be removed. This includes, but is not limited to:

  • Dental work.
  • Wigs.
  • Hairpieces.
  • Head scarfs.
  • Bobby pins, etc.

What is the mask-making process?

The mask-making process can differ slightly depending on the area of your head & neck or brain the treatment will be focused on and if other devices will be used with the mask. Generally, the process is similar and will follow these steps:

Mask being gently stretched over face after being warmed in the water bath.

  • You will be asked to put on a gown for this procedure and for your daily radiation treatments.
  • You will be lying on your back and you will want to continue breathing normally.
  • The mask starts off hard, it is then placed in a warm water bath and becomes pliable after about 3-4 minutes. Gauze, stockinette or other like material may be placed over your head to ensure the mask does not stick to your hair.
  • The mask will be taken out of the water bath, excess water is removed, and it is gently stretched over your face. The mask will feel warm and wet, like a hot towel that would be used during a facial.
  • The mask is then secured to the table using clips.

Therapists using their fingers to mold the mask around the head, face, eyes, ears, and throat.

  • The therapists will use their fingers to mold the mask and ensure that it takes the proper shape of your head, face, eyes, ears, and throat.
  • The holes in the mesh mask will make it easy for you to breathe and see.
  • You will want to remain still while the mask is cooling. The mask takes about 10 minutes to completely cool and harden.
  • After the mask has hardened you will get a CT scan in the position you are in, with the mask on. The mask-making and CT simulation process takes about 30-45 minutes.

Once your mask is made, avoid any major hairstyle changes, including changes to your facial hair.

What other immobilization devices are used with the mask?

You may be asked to use a bite block or mouthpiece with your mask. There are several types of bite blocks, but they all do the same thing. It is placed inside your mouth to hold your mouth and jaw in the same position. It can also be used to help reduce side effects, by depressing your tongue.

Example of a bite block and mouthpieces.

  • Bite blocks are soft pieces of dental wax or plastic that are placed in your mouth. You will be asked to bite it for a few minutes until it hardens.
  • A mouthpiece is like a mouth guard used in sports.

If your provider wants you to use the bite block or mouthpiece it will be placed during the simulation and used every day for treatment with your mask.

Why is the mask important?

The mask is important for your treatment because it holds your head and neck stationary (still) and in the exact position needed for treatment. This helps ensure that your treatment is accurate and as effective as possible. In most cases, after your treatment is complete you are allowed to take your mask home with you.


External beam radiation therapy for cancer. National Cancer Institute. (2018, May 1). Retrieved September 29, 2022, from https://www.cancer.gov/about-cancer/treatment/types/radiation-therapy/external-beam

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