| Přispěvatelé: |
UCL - SST/ICTM - Institute for Information and Communication. Technologies, Electronics and Applied Mathematics, Macq, Benoit, De Vleeschouwer, Christophe, Lambin, Philippe, Thiran, Jean-Philippe, Lee, John |
| Popis: |
This thesis investigates the use of non-rigid image registration, the process of aligning two or more images of the same scene, for two purposes in the radiotherapy treatment process: automatic organ delineation and dose delivery assessment. When done manually, the delineation of organs is tedious and subject to high interobserver variability. Atlas based segmentation, in which an atlas is registered to the patient to be delineated, is a promising tool to do it automatically. However the choice of an appropriate atlas for this method is still an open problem. In this thesis, we show that in the case of brain segmentation because of the high inter-patient variability there is no such thing as an optimum atlas and that multiple atlases strategies are required instead. Moreover, we study the evolution of the quality of the segmentation in terms of number of atlases used. As radiotherapy is usually delivered in daily fractions for several weeks, the anatomical configuration of the patient is not necessarily the same during the entire treatment process leading to an uncertainty on the distribution of the real dose delivered to the patient. With the increase of in-room imaging comes the possibility to estimate the anatomical configuration of the patient from day to day. Using image registration, it is possible to find the transformation between each configuration and a reference configuration allowing to track each voxel of the image along time. The transformation can then be used to warp the dose received at each delivery fraction onto the reference and accumulate them in order to estimate the total dose received by each voxel. In this thesis, we investigate the three steps of this process: voxel tracking, dose deformation and dose accumulation. First, we describe a method to improve the physical behavior of the field in homogeneous regions. Then we study theoretically and empirically the limits and uncertainties linked to dose deformation. Eventually, we show that, for dose accumulation, radiobiological effects are not clinically relevant when using global surrogates but that these effects should not be neglected when using local surrogates. Finally, we show the usefulness of image registration to fuse functional information to radiotherapy planning for brain tumor patients. In a prospective study, we describe how this fusion could contribute to the knowledge of the neurological complications due to irradiation and could lead to the creation of treatment planning based on patient specific functional information. (FSA 3) -- UCL, 2010 |
