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Preparing your child for radiation simulation


Your child is about to start radiation treatments. Most likely, the radiation oncologist or nurse has talked to you about the simulation — the set-up process for radiation. The simulation will be your child’s first contact with radiation. Doing anything for the first time can be stressful for children and teens.

Many patients and their siblings have unspoken fears, questions, and false ideas about what will happen during the simulation. Giving your child correct information that fits his age will help him cope better with this new process and correct any false ideas he might have.

Several staff members will help your child prepare for simulation. A certified child life specialist is one of the team members who will work closely with your family. This staff member 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 him the imaging equipment and walking him through the steps. Your child will learn what his job will be during the process, and if needed, the child life specialist will help develop a plan for coping.

If you do not see an appointment with the Radiation Oncology (RO) Child Life Specialist on your child’s schedule, please call the Radiation Oncology Clinic at 901-595-3655 and ask one of the RO nurses to enter this appointment for your child. The RO nurse can also show you and your child a video that will help explain radiation simulation and treatment. Generally, this will be done when you come for your visit with the radiation oncologist before the simulation.

The simulation process

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

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

In most cases, the therapist will place very small tattoos (freckle size) on his skin using a very small, sterilized needle. Only the tip of the needle is used to make the mark, which is permanent and does not interfere with any other treatment your child will receive.

If the therapist makes a mask for your child, the marks will be on the mask. If he does not need a mask, the marks must remain on his skin until his radiation therapy is complete. Sometimes, the therapists will touch up 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 on the CT table, the plastic piece is placed in warm water. The therapist will give the plastic a few seconds to cool, then place it on the patient’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 your child’s head when he is lying on his back. The mold is a cloth bag filled with beads; the therapist inserts water in the bag. The beads will then harden and the mold will form the shape of the back of your child’s head. This will make it more comfortable for your child to hold his head in the exact position needed for treatments. The mask and head mold forms will be used each treatment day to hold your child’s head in the correct treatment position.

If your child will be lying on his stomach during treatment, the staff will make a facemask similar to the one described above. When your child is lying on his stomach with his 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, similar to a beanbag. If your child needs a vac lock bag for treatment, he will lie on the bag on the CT table. A vacuum pump is used to 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 TBI (Total Body Irradiation). If your child needs an alpha cradle for treatment, he 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, and place it on top of your child like a blanket. The bag will harden and form the shape of his body. The bag will feel warm and will harden in 10–20 minutes. The bag will be used each time your child has radiation treatment to hold his body in the proper treatment position.

Contrast for CT and MRI

In most cases, contrast will be used for either CT or MRI simulation. Please be sure to look at your child’s schedule and follow the guidelines for not eating or drinking before receiving contrast. If contrast is used your child will need an IV. If you have questions about whether or not contrast will be used, please call the Radiation Oncology clinic at 901-595-3655 and ask to speak to your child’s RO nurse.

Guidelines for parents

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


If you would like to schedule a simulation preparation session for your child, talk to your child life specialist. If you are away from the hospital, please call the Child Life department. Locally, dial 901-595-3020. If you are outside the Memphis area, call toll-free 1-866-2STJUDE (1-866-278-5833), extension 3020.

This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

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