Is there any reason to prefer using floating point images over signed 16-bit
images (int16)? The latter take half the disk space. (I'm wondering about
the dynamic range of typical MRI images used in functional brain mapping,
and the effect of the datatype on roundoff error. Typically, it appears
that either floating point or int16 is good enough, given the size of signal
changes and the fact that we're interested in such signal changes in gray
matter, where the signal is well away from 0.)
Also, if I convert analyze-format floating point images to int16 before
using spm, should I follow the following rough algorithm?
max = max of the abs values in the floating point image
SCALE = max/2^15 (put this in the .hdr file, as well as TYPE=4)
int16 image = (round) (fp image/scale)
Best wishes,
Steve Fromm
NIDCD
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