Significant progress has been made in the treatment of childhood cancer, thanks in part to new therapies such as intensity modulated radiation therapy (IMRT). IMRT is a painless, non-invasive therapy used to treat most types of childhood cancer.

IMRT is a technique that adjusts the radiation beams to the 3-dimensional shape of your child's tumor by modulating – or controlling – the intensity of the radiation in multiple small doses. It allows for higher, more effective doses of radiation to be delivered while minimizing exposure to surrounding healthy tissue. This is particularly important for children, since their organs are still developing and growing.

Developed in the late 1980s, IMRT uses computed tomography (CT) and magnetic resonance imagining (MRI) to create 3-D images of the tumor and surrounding tissues. Based on these images, radiation beam directions, shapes and intensities are carefully designed. This precision allows high doses of radiation to be delivered to the tumor while minimizing the radiation and potential damage to healthy tissue.

UCSF Benioff Children's Hospital has one of the best-equipped Radiation Oncology departments in the country and offers two types of IMRT:

  • Multileaf Collimator (MLC) IMRT – MLC-IMRT uses as many as 25 fixed beams to deliver radiation to its target.
  • Serial Tomotherapy – This treatment uses a specially designed IMRT machine that rotates around the patient. The therapy involves several rotations to deliver radiation beams from the most effective angle.


The dose of radiation and number of treatments your child receives depends on the size, location and type of tumor, your child's general health and other factors. Your child's doctor will design a treatment plan that best meets your child's needs.

For each treatment session, your child will spend 15 to 30 minutes in a treatment room. Small amounts of radiation given on a daily basis, rather than a few large doses, help to reduce damage to tissues surrounding the tumor. Weekend breaks between treatments allow normal cells to recover.

The first IMRT session tends to be longer than others so additional X-ray films and checks can be made. Before treatment begins, colored, semi-permanent ink may be used to mark your child's skin to indicate the alignment of the radiation equipment with the targeted area. In the treatment room, the radiation therapist uses the marks to locate the treatment area.

Your child will be carefully positioned on the treatment table. Sometimes, special molded devices are used to help with positioning. The radiation therapist will leave the treatment room before the machine is activated from a control room. You can watch your child on a television screen or through a window in the control room and you and the therapist can talk with your child through an intercom.

During treatment, your child will not hear, see or feel the radiation. If your child does become uncomfortable during the procedure, the machine can be stopped at any time.