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 RGSC Systems and Siemens CT are used to creating 4D CT for gating treatment or Deep Inspiration Breath Hold (DIBH) treatment. Stony Brook's Department of Radiation Oncology 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 the movement of the lightweight chest/abdomen marker with the infrared camera. Images are analyzed using Siemens' 4D software (the 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.
What is DIBH treatment?
Respiratory Deep Inspiration Breath Hold (DIBH) is a specific radiation therapy technique for Breast treatment to spare dose to the heart and lungs. Using the DIBH technique, the radiation is delivered only at certain points during the patient’s breathing cycle. The patient is asked to take a deep breath in and hold their breath during treatment delivery, for about 20 seconds. This, in turn, will limit the amount of the heart and lung that is exposed to the radiation beam, since taking a deep breath in will allow these organs to move out of the treatment field (See sample pictures). DIBH can be also used to minimize internal organ motion for other body sites, such as stomach, pancreas, and liver.