A MODALITY-INDEPENDENT APPROACH TO SPATIAL NORMALIZATION OF TOMOGRAPHIC-IMAGES OF THE HUMAN BRAIN

A modality-independent approach for interactive spatial normalization of tomographic images of the human brain is described and its performa nce evaluated. Spatial normalization is accomplished using a nine-para meter affine transformation to interactively align and adjust the shap e of a subject brain to the reference brain detailed in the 1988 atlas of Talairach et al. A user-friendly software application was develope d using the X-windows Motif environment to guide the user through this process. This software supports data types from a wide variety of tom ographic imagers and produces output in spatially concise formats. The parameters used for spatial alignment and shape normalization are pre sented and methods to apply them discussed. Where normalization parame ters cannot be obtained directly from the image, as with positron emis sion tomography (PET), methods for estimating them are given. Evaluati on of a new four-landmark method to fit the AC-PC Line in 16 magnetic resonance imaging (MRI) studies indicated an average difference assess ed as the distance between the true and fitted AC-PC line at four loca tions of 0.82 mm when using a 2-D weighted fit. The same landmarks wer e evaluated using lower spatial resolution PET-like images simulated f rom the 16 MRI studies. The difference between the PET and MR image vo lumes following alignment was minimal, with mean rotational difference s of less than 0.2 deg and mean translational differences of generally less than 2 mm. Spatial normalization is illustrated for single photo n emission computed tomography (SPECT), X-ray computed tomography (CT) , PET, and MR image volumes. Modality-independent spatial normalizatio n can be consistently and reliably performed with the methods and soft ware presented. (C) 1995 Wiley-Liss, Inc.