1. A system for quantification of medical image data, comprising: spatial transformation obtaining means for obtaining spatial transformation information representing a correspondence between points in a first image and corresponding points in a second image; identifying means for identifying a first image region in the first image; transforming means for transforming the first image region into a corresponding second image region in the second image based on the spatial transformation information; and quantification means for computing a quantification relating to the second image region by accessing image values of the second image within the second image region.