ABSTRACT
Radiation therapy is a leading example for the use of image guidance in localized cancer therapy. Since the discovery of the therapeutic benefits of ionizing radiation more than 100 years ago, great technical advances have been made in the field. A desired radiation dose profile can now be delivered with exceptional precision to targets defined by the radiation oncologist. Advances in imaging technologies result in a more accurate delineation of the target for radiation treatments, whereby clinicians can safely decrease the margin of normal tissue included in radiation treatment fields to account for target uncertainty. Decreasing the margins, and in effect the amount of normal tissue treated, allows for dose escalation and the potential for higher rates of cure with equivalent or reduced normal tissue complications. With technical advances in radiation delivery, defining the target, moreover, the dose required for tumor cure has become a predominant area of uncertainty.
