1. A method of combining images, the method comprising the steps of: obtaining a first image dataset from a subject; obtaining a second image dataset from the subject; segmenting the first image data set; segmenting the second image data set; providing a physiological model; morphing the physiological model to the segmented first image data set to produce a subject specific physiological phantom; registering the subject specific physiological phantom with the segmented second image data set to generate a transform; and applying the transform to the first image data set to provide a fused image.