Imaging in radiotherapy

Radiotherapy, more then ally other treatment modality, relies heavily and o ften exclusively on medical imaging to determine the extent of disease and the spatial relation between target region and neighbouring healthy tissues . Radically new approaches to radiation delivery are inspired on CT scannin g and treat patients in a slice-by-slice fashion using intensity modulated megavoltage fan beams. For quality assurance of complex 3-D dose distributi ons, MR based 3-D verificative dosimetry on irradiated phantoms has been de scribed. As treatment delivery becomes increasingly refined, the need for a ccurate target definition increases as well and sophisticated imaging tools like image fusion and 3-D reconstruction are routinely used for treatment planning. While in the past patients were positioned on the treatment machi nes based exclusively on surface topography and the well-known skin marks, such approach is no longer sufficient for high-accuracy radiotherapy and sp ecial imaging tools like on-line portal imaging are used to verify and corr ect target positioning. Much of these applications rely on digital image pr ocessing, transmission and storage, and the development of standards, like DICOM and PACS have greatly contributed to these applications. Digital imag ing plays an increasing role in many areas in radiotherapy and has been fun damental in new developments that have demonstrated impact on patient care. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.