Accurately tracking tumor position is a critically important factor when maximizing radiation dose to the tumor and limiting normal tissue exposure. In the past, this task has been complicated in regions of the body where respiration causes tumor motion, i.e., organs of the chest and abdomen, such as the lungs, stomach, pancreas and liver. To overcome tumor motion difficulties, Varian® Medical Systems' Real-Time Position Management Respiratory Gating System (RPM) and GE®'s Advantage 4D CT Software were developed. Stony Brook's Department of Radiation Oncology now offers this state-of-the-art technology.
What is respiratory gating?
Gating is a system that tracks a patient's normal respiratory cycle with an infrared camera and chest/abdomen marker. The system is coordinated to only deliver radiation when the tumor is in the treatment field.
What can a patient expect when treated with the RPM respiratory gated system?
The patient is first imaged on the CT Simulator while tracking movement of the lightweight chest/abdomen marker with the infrared camera. Images are analyzed using GE's 4D software (fourth dimension being time) to accurately determine tumor motion. Without gating, images can be blurry. With a gating system, images are clear and crisp, allowing for more accurate treatment planning.
When the patient arrives for treatment, the chest/abdomen marker will be placed in the same location as set for imaging. The infrared camera will track the patient's breathing cycle as he or she is allowed to breathe in a relaxed manner. The gating system will automatically detect when to give radiation according to the patient's specific respiratory cycle. The beam will be held off for disruptions in the breathing cycle, such as coughing or sneezing. Using the respiratory gating system, the patient will receive better tumor control and less normal tissue complications without sacrificing comfort.