Respiratory gating is a process where your breathing cycle is matched to the radiation treatment. This is most often used for tumors in the lung. When you breathe, your chest and the organs within it move up and down several inches. This presents somewhat of a moving target when aiming the radiation beam. The size of the treatment beam often needs to be made larger to account for motion.
Respiratory gating allows for the radiation beam to be on only during certain phases of the breathing cycle. This technique allows your physician to deliver higher doses of radiation to the tumor because the surrounding healthy tissue can be spared. Respiratory gating is combined with 3-D Conformal radiation therapy or IMRT and involves pre-planning appointments before treatments can begin.