Dynamic Targeting^® IGRT (Image-Guided Radiotherapy) from Varian Medical Systems

HOW IT WORKS

Tissues, organs, and many tumors are not rigidly fixed in one position; they move around inside the body due to natural physiological processes. For this reason, they are not always in the exact same position each time a patient is positioned for treatment. In addition, tumors can move several centimeters due to a patient's normal respiratory cycle.

For Dynamic Targeting IGRT, the medical linear accelerator, or treatment machine, is outfitted with a number of sophisticated imaging devices that provide the clinician with images that help to guide the treatment.

An X-ray system mounted on a robotic arm is rotated around the body to gather images that pinpoint a tumor's exact location just prior to treatment. These images are then compared with reference images (MRI, CT or other kinds of scans) in order to determine if the tumor is where it is expected to be, or off by some margin. Sophisticated software programs calculate how to move the patient so that the tumor is directly in the center of the treatment beam.

Another accessory for "respiratory gating," can be used to coordinate treatment with respiration, to compensate for tumor motion due to the patient's breathing. This is useful for treating lung cancer and other tumors in the chest or abdomen that move as the patient breathes.