Recently it has become clear that there are strong relationships between genetic information and measurements in brain imaging. For example, genes on chromosome 12 are related to a reduction of the hippocampus volume, which characterizes the Alzheimer's disease. This can be very important in order to better understand the genetic predisposition to neurodegenerative diseases. Diffusion tensor MRI is an imaging technique that provides detailed information about the integrity of white matter tracts in the brains A major problem for the analysis of diffusion MRI in population studies is that the data has a relatively low resolution and therefore is insufficient in details. There is a need for image processing in order to exploit the extremely large populations and thereby allow for accurate measurements in the diffusion images. The main goals of this project are