A technique for reliably measuring brain atrophy based on image data, such as data collected as part of an MRI scan of a subject's brain. Rather than measure anatomical features of the brain in one of the scan planes as output by an MRI system, the image data is reformatted to generate a slice that may be transverse to those scan planes. The transverse slice is generated by determining a location of anatomical landmarks and reformatting the image data to represent a slice through these anatomical landmarks. The Anterior and Posterior Commissures are useful landmarks and ventricle area is a useful characteristic to measure from the slice. The rate of change of this measured characteristic can be tracked to determine disease progression and may be useful for diagnosis or evaluation of treatments, and the technique may be applied during clinical trials.
