Respiratory Motion System
Treating cancer with radiation therapy is a complex balance of delivering the appropriate dose of radiation to destroy a tumor while affecting as little of the surrounding healthy tissue and organs as possible.
Achieving that goal is much more complicated when the tumor is a moving target — affected by a patient’s breathing.
That’s why Concord Hospital Payson Center for Cancer acquired a Respiratory Motion Tracking System this spring to help ensure radiation is delivered at precisely the correct moment as a patient inhales and exhales.
“The challenge is knowing where the tumor is as the patient breathes,” said Therapy Supervisor Tammy Newell. “When is the best time the machine should be on relative to where the tumor is in the body, based on the patient’s breathing?”
To develop a treatment plan, Payson specialists use sophisticated 4D CT scanning to define the size and shape of a tumor and map how it moves as a patient breathes. One of Payson’s medical dosimetrists, George Bourg, analyzes the scans with a radiation oncologist and can determine, for example, that the most effective instant for a radiation dose for a certain patient is when the patient’s lungs are inflated from 40-to-60 percent.
A respiratory motion sensor placed on a patient’s abdomen during treatment links the rise and fall of the chest to the results of the internal scans. When the chest reaches the precise level indicated by the scans, a camera detects an infrared signal from the sensor, triggering the radiation machine to
turn on and off.
Before 4D imaging, cancer specialists knew tumors moved during breathing, but they did not know exactly how much. To account for the movement, treatment plans included larger targets for radiation, which meant more healthy tissue was affected.
The new system allows for more precise targeting, especially for cancers in the lungs, liver and pancreas — reducing harm to healthy tissue.
“With patients whose lungs are already compromised, every bit of lung tissue is important,” Bourg said.
Adding the complex system and acquiring the expertise to use it to benefit patients involved Payson’s entire Radiation Oncology Department, with support from Concord Hospital’s willingness to constantly improve its cancer care.
“The message is that we want to treat the patients the best that we can and that we are very serious about investing in the technology to be able to do that,” Bourg said.