MR-Only Methodology

MRI-only radiation therapy is a rapidly expanding research field which promises to integrate the excellent structural and functional imaging information available from MRI with MRI-based delivery systems. The purpose of this chapter is to provide an overview of the main methods for generating substitute CT (sCT) from MRI scans for MRI-only radiation therapy treatment planning. The chapter commences with a brief discussion of MR image acquisition and image preprocessing. As many sCT generation methods currently rely on identifying tissue types, a brief overview of image segmentation is provided. Four broad categories of sCT generation are then described: bulk density, tissue class segmentation, learning approaches and atlas-based conversion. Finally an overview of the first clinics treating patients with external MRI-only radiation therapy planning is provided.

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