Any deviation from this shape indicates anisotropy in the data.

The 3D representation for a fixed distance is a closed digital surface, which is called an indicatrix. Projections of the orientation histograms can be obtained as illustrated in (Figure 2) for a control subject and an AD patient. Figure 2. Projections of the orientation histogram on the z=0 plane obtained from MRI T1, images: from an Alzheimer’s disease patient (left) and a healthy volunteer (right). The isotropic features of the histogram are related to brain pathology. Feature extraction Three features are used to analyze the shape of the Inhibitors,research,lifescience,medical 3D indicatrix12: the anisotropy coefficient, the integral anisotropy measure or standard deviation, and the local mean curvature. Another set of features can be extracted by expanding the indicatrix in terms of spherical harmonics. The coefficients Inhibitors,research,lifescience,medical of such an expansion can characterize any 3D closed surface: coefficient A0,0 is the mean radius of the indicatrix; any other nonzero Inhibitors,research,lifescience,medical coefficient represents different types of anisotropy. GW-572016 Anisotropic features were extracted from four brain regions: the whole brain, white matter, gray matter, and the border between gray and white matter. In ever single region, five different, distances d were used: 0.9375, 1.5, 2, 2.5, and 3 mm. MMSE score and correlation with the isotropy coefficient The MMSE score Inhibitors,research,lifescience,medical is used to

detect dementia. The maximum score is 30 (typically above 29 for healthy volunteers). Scores between 10 and 24 are considered to indicate mildto-moderate dementia cases, and scores below 10 indicate severe dementia. The scores obtained in the AD patients (named AD1 to AD13)

and the control volunteers (named COl to C012) are displayed Inhibitors,research,lifescience,medical in Table II. Two of the scores do not match the clinical diagnosis: AD3 and C02. Table II. Mini-Mental State Examination (MMSE) score for subjects with Alzheimer’s disease (AD1 , AD2, AD3, etc) and controls (C01 , C02, C03, etc). While many features correlate well with the M’M'SE scores, (Figure 3) illustrates the best correlation (-0.876) with the MMSE score, which was obtained for the feature A1,1 in gray matter for a distance of 0.9375 mm. Figure 3. Feature |A1, 1| in gray matter for d=0.9375 mm versus aminophylline the score on the Mini-Mental State Examination (MMSE). • Alzheimer’s disease patient (AD1 , AD2, AD3, etc); • control volunteers (C01.C02, C03, etc). Reproduced from reference 13: … Subject AD3 is interesting because this patient, was imaged before the onset of the first clinical symptoms, at a time when there may have been ongoing structural brain changes. Discussion and conclusion The GLDH method can be used to produce many features that strongly correlated with the MMSE scores when applied to the gray matter components of the MRI T1 scans.