Slide show: Radiation therapy treatment planning

Before you begin external beam radiation treatment, your radiation therapy team carefully plans every aspect of your treatment. Your radiation therapy plan involves taking detailed images of your body and marking the precise areas that will receive the beams of radiation. Your radiation therapy team positions you just right so that only a minimal amount of healthy tissue will be in the path of the radiation. Planning gives you insight into what to expect during your radiation treatment.

Here's a look at the treatment planning process that occurs before radiation therapy begins. This planning process is called radiation simulation. Keep in mind that everyone's treatment is different, so talk to your radiation therapy team about what to expect during your treatment planning.

Your radiation therapy team determines how you'll be positioned on the treatment table — whether you'll lie on your back, stomach or side. Team members take into consideration where your treatment is focused, your ability to lie still and what positions will be most comfortable for you.

It's crucial to place you in a position that optimizes your radiation treatment. But it's also important to find a position that you can hold for 15 to 30 minutes.

To make you more comfortable, your radiation therapy team might use devices to position you. The form in this picture supports your head if you need to lie on your stomach. Other devices might prop you up if you're lying on your back or raise an arm or leg if needed.

In order to ensure that you'll be in the exact same position for each of your radiation treatments, your radiation therapy team might use devices to hold you in place. This way, treatment is delivered to a precise area during each radiation therapy session, and a minimal amount of healthy tissue receives high-dose radiation.

A variety of immobilizers exist. A cushion-like device called a Vac-Lok bag — similar to a beanbag with the air removed — holds its shape, cradling you in the optimal position.

Another type of immobilization device used during radiation therapy is a thermoplastic mask. You might use this mask if you're receiving radiation to your brain, 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.

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

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. Some marks are drawn on your skin with a marker. You can wash these marks off once your final treatment is completed.

Other 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.

Your part of radiation therapy treatment planning is done. Your radiation therapy team now develops a radiation plan that's best for you. Your plan might involve a single beam of radiation, or it could include multiple beams. You may wait several days after simulation before you begin treatment.

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 if you have any concerns. That way, you'll know what's occurring as you begin your radiation therapy.