The body does not always remain still during treatment, and for precise treatment of tumors of the lung or abdomen, even normal breathing can present a challenge. In these cases, respiratory gating, also known as 4-Dimensional CT, is used. The four-dimensional CT scanner, equipped with respiratory gating technology, addresses tumor motion during the process of radiation planning. Movements of the tumor can be taken into account, so the radiation beams can encompass the tumor in all phases of the breathing cycle.