CT Simulation with 4-D Gating assists the radiation oncologist with planning for the delivery of radiation to tumors that move when the patient breathes. Using an infrared camera connected to a CT scanner, four-dimensional images are generated in a clear video sequence that shows exactly how the tumor moves during the patient’s normal breathing cycle. Clinicians are then able to determine how to deliver the desired radiation dose to the tumor with the most precision and with minimal risk of damaging healthy surrounding tissue.