Integration of multimodality imaging data for radiotherapy treatment planning

This thesis describes new methods which permit the quantitative integration of three-dimensional imaging data sets. These methods are used to combine the diagnostic and physical information provided by positron emission tomography (PET), nuclear magnetic resonance (NMR) imaging, and x-ray computed tomography (CT) into treatment planning procedures for radiotherapy. Integration of information from the different imaging modalities is treated as a two step process. The first step is to determine the set of geometric parameters relating the coordinates of two imaging data sets. Four different methods developed to determine these parameters are presented. Each method makes use of a specific geometric object contained in the two data sets to determine the parameters. These objects are: (1) anatomical and/or fiducial points, (2) attached line markers, (3) anatomical surfaces and (4) outlines of anatomical structures. In the first three cases, the coordinates describing these objects are used to define a merit-function that measures the geometric mismatch between the two imaging studies. The necessary parameters are calculated by minimizing this merit-function using non-linear optimization techniques. In the last case, the parameters are determined manually using graphical feedback. The second step in the integration process is to transfer outlines of structures drawn on the image of one imaging study to the images of another study. Solids modeling techniques are used to construct a surface from the two-dimensional outlines. This surface is transferred to another imaging study using the parameters calculated in the first step. The geometric parameters are also used to reformat the images of one study to match the orientation and scale of the images of another study