The goal with radiation therapy is to treat the defined tumor and spare the surrounding normal tissue from receiving dose above specified tolerance doses. There is evidence of improved local control and survival with higher doses of radiation, however, at the same time there is the need to spare normal tissues from higher doses of radiation. Technologies that allow the delivery of an increased radiation dose to the tumor while sparing normal tissue have the potential of improving the therapeutic ratio. However, the development of these technologies has been hampered by organ respiratory motion particularly in the case of the lungs and liver. Inadequate radiation coverage of a tumor secondary to organ motion can lead to delivering a lower dose to a portion of the tumor. Making the field of radiation larger to account for organ motion results in unnecessary radiation dose to surrounding healthy tissues. It is therefore desirable to document the extent of motion of the organ in question prior to carrying out the radiation treatment planning. The organ motion impacts directly on the radiation dose distribution in the treatment volume.
