Abstract ID: 17197 Title: Therapy Symposium AAPM 2011 Abstract Adaptive Image-Guided Radiation Therapy: A Physician’s Perspective Arno J. Mundt MD Professor and Chair President-Elect, American College of Radiation Oncology (ACRO) Department of Radiation Oncology University of California, San Diego (UCSD) Image guided radiation therapy (IGRT) today is focused on the use of in-room imaging technologies to improve patient setup and target localization. IGRT in the future, however, will also include the use of imaging to adapt treatment to changes in the tumor (and patient) during treatment. One of the most important changes which can be adapted to is in morphology of both the tumor and surrounding normal tissues. Newer in-room volumetric imaging opens the door to adapting to such changes. Discussion of adaptive IGRT quickly turn to the technical issues involved including automated segmentation and deformable registration. However, a fundamental understanding of the variety and frequency of morphologic changes which occur is crucial to the development of adaptive IGRT strategies. This lecture reviews the morphologic changes which occur during treatment of patients with CNS, Head and Neck, lung, gastrointestinal, breast, gynecologic, genitourinary and pediatric tumors. Published data on adaptive IGRT approaches in a variety of tumor sites will also be presented.