Developments in MRI-based radiation treatment planning

摘要

The objective of this work is to develop a com-prehensive radiation treatment planning (RTP) procedure for the therapy of cancer sites based solely on magnetic resonance imaging (MRI), MRI-based RTP. We also investigate the ap-plications of this procedure to a linac-MR system, i.e. a 6 MV therapy accelerator coupled to a bi-planar 0.2 T permanent magnet. The proposed technique consists of a) correction of MR images for scanner-related and patient-induced distor-tions by using phantom measurements and numerical simula-tions, respectively, b) segmentation of anatomical structures relevant to dosimetric calculations (i.e. soft-tissue, bone and air), c) conversion of MR images into computed tomography (CT)-like images, by assigning bulk CT values to anatomical contours, along with RTP dose calculations, and d) CT+MRI and MRI-based treatment plan comparison. In addition, for a linac-MR system the RTP dosimetric calculations were per-formed in the presence of a 0.2 T external magnetic field. Both scanner-related and patient-induced distortion fields were determined. Treatment plans were generated to validate the MRI-based RTP procedure.