Average brain models: A convergence study

We present a completely automatic method to build stable average anatomical models of the human brain using a set of magnetic resonance (MR) images. The models computed present two important characteristics: an average intensity and an average shape, both in a single image. We provide results showing convergence toward the centroid of the image set used for the computation of the model. In particular, the RMS distances between the model and the MR images contained in the set stabilize in a range of 2.88 to 3.36 mm from a range of 4.62 to 5.51 mm initially after only one iteration. As for the influence of the reference image chosen for the model construction, this is minimal with differences of about 1.0 mm, from approximately 3.5 mm initially. These results ensure the usefulness of our approach. (C) 2000 Academic Press.