ImportDTI[folder]

imports xx.dat,yy.dat,zz.dat,xy.dat,xz.dat and yz.dat from the given folder.

ImportDTI[folder,add]

imports xx-add.dat, yy-add.dat, zz-add.dat, xy-add.dat, xz-add.dat and yz-add.dat from the given folder.

ImportDTI[{file₁,file₂,..}]

imports the given *.dat files.