5G05-Integrating Advanced Imaging and Radiotherapy Methods

C Clifton Ling, PhD

Departments of Medical Physics

Memorial Sloan Kettering Cancer Center

New York, NY 10021

            Over the past century since the discoveries of Roentgen, Becquerel and Curie, there has been incredible progress in the use of ionizing radiation for cancer diagnosis and treatment.  In radiotherapy, the clinical implementation of 3-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) will likely increase the effectiveness of this treatment modality.  Within the past decade, IMRT has emerged, leading to further improvement in dose distribution conformality. 

            The "new" concept of IGRT (image-guided radiotherapy) may appear "retrograde" since from the very beginning radiotherapy has been image-based, in fact initially using the same X-ray equipment for diagnosis and therapy.   However, the IGRT of the twenty-first century has its impetus in the concomitant but independent development of advanced imaging and radiotherapy methods, and indeed in the re-integration of imaging and treatment devices.  Specifically, stereotaxic or volumetric imaging devices are now combined with radiation treatment units to provide image-guidance in real-time (or almost real-time).  Perhaps the present approach would be more aptly called IG(RT)², for radiotherapy with image-guidance in real-time.

            Concomitant with the advances in radiation treatment, much development occurred in imaging, especially in CT, MRI and PET.  Totally unanticipated until the last decade is the impact of the human genome project and the emerging possibility of imaging biological processes.  Indeed, the spectacular advances in our understanding of cellular and molecular processes and their application to imaging are providing new types of images, with a wide spectrum of “biological” information, including metabolic, biochemical, physiological, functional and molecular (genotypic and phenotypic). 

            The improvement in the dose distribution conformality of IMRT, and the emerging ability of imaging that can give information about factors (e.g. tumor hypoxia, tumor burden) that influence radiosensitivity and treatment outcome, avail tremendous opportunities and bring new challenges.  In this presentation I shall discuss some aspects of this ongoing synthesis of advances, in what some would say is “physics meets biology”.