In couch tracking, the patient is moved by the robotic treatment couch. Such robotic treatment couches are in use with conventional, widely available C-arm linear accelerators, and, therefore, are readily available for implementing couch tracking. The patient is placed on a couch which moves in the opposite direction of the tumor motion. The goal is to minimize the patient's tumor motion relative to the radiation, which in turn allows the margins to be decreased. The margin decrease might ultimately lead to a reduction of side effects, e.g. pneumonitis.