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Preparing for Radiation Simulation

One of the ways to prepare for radiation is to go through radiation simulation. This is an appointment where the team plans your child’s radiation therapy.

Many people have unspoken fears, questions, and false ideas about what happens during radiation. Give your child correct information that fits their age. This will help them understand the process. You can also correct any false ideas they might have.

Preparing your child or teen for radiation will help:

  • Reduce their anxiety
  • Develop their trust in you and the hospital staff
  • Give them a sense of control over what is going to happen
  • Identify parts of the treatment that may be hard for them
  • Develop ways to cope

Talking to your child about radiation

If your child or teen understands radiation, they can cope better with simulation and treatments. Use the word “radiation” openly with your child or teen. They will be familiar with the word and more willing to ask questions. The ideas below can help you talk with your child or teen about radiation in words that fit their age.

Verbal Toddler: Use words your child knows such as “boo-boo,” “owie,” and “medicine.” Explain that the “medicine” will go to the “boo-boo” or “owie” while they are sleeping (under anesthesia).

Preschooler: Explain what will happen in simple terms. “You will be given sleepy medicine (anesthesia) so that your body is very still. While you sleep, radiation will come from the machine and go to XXXX (naming the area of the body where radiation will go). Radiation is a medicine that you can’t see, hear, or feel.” (Another example: “Inside your tummy is sick, and the radiation needs to go to that place. While you sleep, the machine will send the radiation to your tummy.”)

Early School-Age: You can explain radiation as “a type of treatment that you cannot see, feel, or touch. A machine sends invisible rays to the sick parts of your body. Your job is to hold your body still so that the radiation only goes to the parts that are sick.”

School-Age: Many children at this age have begun learning about cells. You may want to say something like, “Radiation is used to stop the sick cells in your body from growing or spreading. A machine will send invisible rays to the sick cells in your body. You will not see, hear, or feel the radiation. Your job is to hold very still so that the invisible rays only go to the sick cells.”

Teens: At this age, your teen may want to talk with the doctor to hear treatment explained in depth.

How a child life specialist can help

Several staff members will help your child prepare for simulation and radiation treatments. A certified child life specialist is one of those team members. This person will offer a preparation session that fits your child’s age.

In this session, the child life specialist will help your child know what to expect by showing the imaging equipment and explaining the steps. Your child will learn what their job will be during the process. If needed, the child life specialist will help develop a plan for coping.

What happens during radiation simulation

Because radiation can damage normal cells along with cancer cells, the radiation oncologist wants to make sure your child’s body is in the best position for treatments. The correct position can help kill more cancer cells while doing as little damage as possible to normal cells.

During simulation, the radiation oncologist will decide the best treatment position for your child. A mask or body mold might be made to help hold their body in the same position for each treatment.

Your child will have a CT scan and maybe an MRI to make sure their body is in the best position for treatments. When they are in the correct position, the therapist will make marks on your child’s skin with a permanent marker or paint pen. The therapists will use these marks to help repeat the same treatment position each day.

If the therapist makes a mask for your child, the marks will be on the mask. If your child does not need a mask, the marks must remain on the skin until radiation therapy is complete. Sometimes, therapists will reapply the marks to make sure they are easy to see.

Devices to help your child hold still


The therapists may use a mask (called an Aquaplast® mask) to hold your child’s head in the proper treatment position. The mask is made with a flat piece of plastic that has small holes in it, like mesh. When your child is in the correct position, the plastic piece is placed in warm water. The therapist will give the plastic a few seconds to cool, then place it on the child’s face and stretch it down over the chin. The warm water loosens the plastic, which helps the mask form over the face. It will feel very warm and wet but will cool quickly. Many patients say it feels like a warm washcloth on their face. As it dries, the plastic hardens to form a facemask.

Your child will be able to breathe easily through the holes in the mask. The therapist will also make a mold to go under the head when your child is lying on their back. The mold is a cloth bag filled with beads; the therapist inserts water in the bag. The beads harden, and the mold forms the shape of the back of your child’s head. This makes it more comfortable for your child to hold their head in the exact position needed for treatments. The mask and head mold forms are used each treatment day to hold your child’s head in the correct position.

If your child will be lying face down during treatment, the staff will make a facemask similar to the one described above. When your child is lying on their stomach with their face in the mask, the therapist will place an oxygen tube in the space between the table and the mask so that your child will have fresh air to breathe.

Vac lock bag

The therapist may use a vac lock bag to hold your child’s body in the proper treatment position. A vac lock bag can be used to support the head, abdomen, leg, or another part of the body. The vac lock bag feels squishy, like a beanbag. If your child needs a vac lock bag for treatment, they will lie on the bag on top of the table. A vacuum pump will remove air from the bag, causing the bag to mold around your child’s body.

Alpha cradle

This will be used if your child needs total body irradiation (TBI). If your child needs an alpha cradle for treatment, they will lie on the TBI couch on top of a vac lock bag. The radiation therapist will pour a foaming solution inside a plastic bag called an alpha cradle. Then they place it on top of your child like a blanket. The bag hardens and forms the shape of the body. The bag will feel warm and will harden in 10 to 20 minutes. The bag will be used each time your child has radiation treatment to hold their body in the proper treatment position.

Contrast for CT and MRI

In many cases, contrast is used for CT or MRI simulation. Be sure to look at your child’s schedule. Your child must follow the eating and drinking guidelines before receiving contrast.

If you have questions about whether or not contrast will be used, speak with your care team before the appointment.

How to help your child through simulation and treatments

  • Be honest. Explain the steps of the simulation and treatments in simple terms that your child can understand. The simulation is the set-up portion of radiation, including scans and positioning.
  • Give reasons for the simulation and treatments. Let your child or teen know that they did not do or say anything to cause the disease or this treatment.
  • Explain to your child or teen what their job will be during the simulation and treatments. Praise their them for being helpful by saying things such as “You did a good job holding your head still.”
  • Offer choices when you can, such as listening to a favorite CD or recorded book, or just resting during the simulation and treatments.
  • Provide chances for medical play. This can help your child or teen become familiar with the medical supplies, imaging machines, and sequence of events. It can also help them gain a sense of control.

Guidelines during simulation or radiation treatments

  • One parent or guardian is welcome to walk the child back for the simulation. Then, that parent returns to the waiting area until the process is complete. This helps the staff focus on the patient and the simulation.
  • To help your child hold still, they may need to be sedated. That means the care team gives them medicine to help them sleep during the simulation. Your medical team will make this decision. You or another family member may stay with your child until they fall asleep. The sedation team members will monitor your child the entire time. They will call you to the recovery room when your child is waking up.
  • If your child’s treatment requires a mask, be sure that their hair is in the same style each day of the simulation and treatments. Sometimes, your child may need a haircut before the simulation or treatments. This ensures that the mask holds your child’s head in the correct position each time.
  • In most cases, the therapist will ask your child to remove some clothing during the simulation to perform scans and to place the marks on their skin. Staff will give your child a hospital gown. When your child dresses the morning of the simulation, try to avoid clothing with metal snaps, zippers, or buttons. The best clothing choices may include T-shirts with sweatpants, pajama bottoms, or other elastic waist pants. If your child’s clothing has metal pieces where the body will be scanned, they must change into a hospital gown before the simulation.
  • For safety reasons, siblings must remain in the waiting area during simulation. Please make sure you have someone in the waiting area to watch siblings before you arrive for the simulation.

Key Points

  • Radiation simulation is an appointment that helps your care team know where to focus radiation. They also may create special items to help your child hold still so the radiation goes where it should at every appointment.
  • Preparing your child for radiation can help them feel less stressed about their treatments.
  • Work with your health care team to prepare your child for their radiation treatments. Your care team wants to support your family as much as possible.

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Reviewed: September 2022