Different anisotropy indices
such as generalized anisotropy (GA) and generalized fractional anisotropy (GFA)
for HARDI data have been reported, but they have their own limitations. Here we
propose a new anisotropy measure (HFA) for the HARDI data that is rotationally
invariant. The new proposed measure is compared with GA and GFA using the
contrast-to-noise ratio and coefficient of variation as the metrics for three
white matter regions. HFA and GFA have shown better CNR than FA and GA
in two and three crossing regions. The results described above were very
similar across all the five subjects.
