If a peak is found before a hill begin point, the ratio is reduced by 0.1 and the process is restarted. Neither csf, which is a small class, nor pathology show up as a clear peak in any of the histograms. It was found that pathology and csf could be partially distinguished by viewing the voxel intensity as a percentage of the range of intensities in either T1 or T2 weighted images. This approach enabled rules to be generated for csf and pathology. The rules are applied to all voxels, but will not classify all voxels.
Spatial information is used to assign memberships to voxels which are unclassified.
A, if all the 8 surrounding voxels have zero membership in that class, then the isolated voxel's membership for class A is made zero. This step is aimed at reducing classification errors. The pathology rule applied to normal slices will incorrectly label a small number of voxels as pathology. A side effect of treatment is that the MR characteristics of gray and white matter are changed and the PD histogram becomes something like that shown in Figure 8 . Our strategy is to edge detect and remove the edge voxels or sharpen the boundary between gray and white matter.