Voxel-based morphometry using the RAVENS maps: Methods and validation using simulated longitudinal atrophy

Statistical analysis of anatomical maps in a stereotaxic space has been sho wn to be a useful tool in population-based studies for quantifying local an atomical differences or changes, without a priori assumptions about the loc ation and extent of the regions of interest. This paper presents an extensi on and validation of a previously published methodology, referred to as RAV ENS, for characterizing regional atrophy in the brain. A new method for ela stic, volume-preserving spatial normalization, which allows for accurate qu antification of very localized atrophy, is used. The RAVENS methodology was tested on images with simulated atrophy within two gyri: precentral and su perior temporal. It was found to accurately determine the regions of atroph y, despite their localized nature and the interindividual variability of co rtical structures. Moreover, it was found to perform substantially better t han the voxel-based morphology method of SPM'99. Improved sensitivity was a chieved at the expense of human effort involved in defining a number of sul cal curves that serve as constraints on the 3D elastic warping. (C) 2001 Ac ademic Press.