Checkup

New Radiation Therapy Opens the Gate
to More Accurate Treatment

Radiation Oncologists Synchronize Patient's
Breathing Cycle with Radiation Beams

Drs. Christopher Serago and Laura Vallow say that patients with breast, lung, liver, pancreas and possibly kidney cancer will be evaluated to see if respiratory gating can be used in their radiation therapy.

Learn more about the
Department of Radiation Oncology.

Every time you breathe in, your chest moves one to two inches. Not a problem usually. But when you're being treated with powerful radiation beams that are precision-coded to hit a certain target, every little move matters. Now, with a new technology offered at Mayo Clinic that more effectively treats cancerous tumors located in the upper abdomen and chest, patients can breathe even easier knowing that the treatment they're getting is highly accurate.

This new advance in radiation oncology is called respiratory gating. Because organs in the mid-to-upper torso move with every breath, a tumor there may move up to two inches with each inhale. Respiratory gating synchronizes delivery of radiation with the patient's own breathing cycle, which allows radiation oncologists to treat tumors with a high dose of radiation without exposing too much normal tissue.

"There is a correlation between the increased dose of radiation to normal tissue and an increased risk of complications," says Dr. Laura Vallow, a Mayo Clinic radiation oncologist. "We're trying to minimize the dose of radiation delivered to normal tissue while continuing to treat all of the disease."

Using a multislice, four-dimensional CT scanner (the fourth dimension is time) and computers capable of storing and manipulating the necessary 1,500 CT images, physicians measure the patient's range of motion during respiration, decide whether respiratory gating is appropriate and customize the treatment field to the patient. During actual treatment, the radiation beam is continuously turned on and off to synchronize delivery of radiation during the optimal point of the patient's breathing cycle.

"This is not perfect, because the way you breathe today and the way you breathe tomorrow are not necessarily the same," says Mayo Clinic medical physicist Christopher Serago, Ph.D. "If you try to breathe like a machine, you can't do it. But this is a better approximation than we've ever had before."

It's usually necessary to treat some margin of healthy tissue with radiation for two reasons. The first is to include microscopic cancer cells not visible on imaging studies. The second is to allow for variables such as patient movement, including breathing, during treatment.

"Respiration is hard to predict from patient to patient," Serago says. "In the past if you wanted to be very conservative, you might put up to a 3-centimeter margin around the tumor to account for respiratory motion. With gating, the treatment margin may be reduced and customized to the individual patient."

Serago and Vallow say that patients with breast, lung, liver, pancreas and possibly kidney cancer will be evaluated to see if respiratory gating can be used in their radiation therapy.

Info:
Department of Radiation Oncology
(904) 953-1040

To request an appointment with a physician in the Department of Radiation Oncology,
call (904) 953-1000 or complete our online appointment request form: