Mayo Clinic Health Library

Slide show: Radiation therapy treatment planning

Updated: 01-12-2012

Immobilizing your body

Photo of a man lying down, surrounded by radiation therapy team

Before you begin external beam radiation treatment, your radiation therapy team carefully plans your treatment in a process called radiation simulation. Radiation therapy treatment planning usually involves positioning your body, making marks on your skin and taking imaging scans.

Your radiation therapy team determines whether you'll lie on your back, stomach or side during treatment. It's crucial to find a position that optimizes your treatment, but is comfortable enough to hold for 15 to 30 minutes.

A variety of immobilizers may be used to ensure you'll be in the same position for each radiation therapy treatment. Here, a special cushion-like device that holds its shape is used.

Immobilizing your head

Photo of the positioning of a thermoplastic mask

Another type of immobilization device used during radiation therapy is a thermoplastic mask. This mask might be used if you're receiving radiation to your head or neck. The firm plastic mask is molded to your face and secured to the table, so it gently holds your head in place. Some masks may extend to cover your shoulders, as well.


Photo of a computerized tomography (CT) machine

Once you're correctly positioned, your radiation therapy team takes images of the area of your body to be treated. You might undergo X-rays or computerized tomography (CT) scans. This helps your radiation oncologist determine the exact spots where treatment will be focused.


Photo of treatment marks being made on a man's body

To indicate the exact spot where radiation should be aimed, your radiation therapy team marks your body. What type of mark you receive depends on your cancer and your treatment. In certain cases, marks are drawn on your skin with a marker. You can wash these marks off once your final treatment is completed.


Photo of a dime next to a small tattoo

Most of the time, marks are permanent. Tiny tattoos — small dots of ink under your skin — are permanent marks that can't be accidentally rubbed off or washed away. This photo shows how small the tattoos are — about the size of a freckle. Sometimes you'll need multiple tattoos. If you're concerned about receiving tattoos, talk with your radiation therapy team.

Treatment begins

Photo of a person undergoing radiation therapy

Once planning is complete, you can begin radiation therapy. During treatment, you'll be placed on a table in the same position that you were placed in during the radiation simulation. The positioning or immobilization devices used in simulation will now be used during your radiation therapy.

The radiation therapy treatment planning process provides a good opportunity for you to ask questions about what will happen during your treatment. Be sure to ask your treatment team about any concerns you might have. That way, you'll know what's occurring as you begin your radiation therapy.

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