Respiratory Gating is a system that uses an infrared video system to track a lightweight marker block placed on the patient’s abdomen. The tracking camera mounted on the wall sends infrared light toward the marker block. The gating system identifies the patient’s periodic breathing pattern by processing a signal generated by the light as it is reflected back. This information is then used to determine when the tumor is in a certain zone during the respiratory cycle.
This is also done during the PET/CT simulation so the images acquired for treatment planning can be synchronized with the respiratory cycle. Then, during treatment, the beam is automatically “gated” on and off as the tumor moves in and out of the selected zone, allowing for higher doses and much greater accuracy.