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fScan Reference Manual, Chapter 2 (CmdLineOptions:Expr): segment
usage: -expr segment [value flag] – cluster contiguous non-zero voxels into different ROIs
The SEGMENT command process a 3-D image map looking for voxel values greater than VALUE. Each time it finds such a voxel it uses a variation of the flood function to find all other voxels greater than VALUE contiguous with the first, and assigns all those values a new “cluster” number. Cluster values start at 1, and increase by 1 for each new cluster found.
VALUE: default is 0
0 - default
1 - look for negative voxel values, less than -VALUE