FSL gurus,
I am having a problem with conversions and resampling of fsl stat files.
So basically, what I want to do is this :
tstat1 (*.feat/stats folder 32 bit img file)
to (Conversion 1)
tstat1_highres (resampled to highres space using flirt)
to (Conversion 2)
tstat1_highres_16 (converted to a 16bit signed short image)
I have a couple questions regarding each of the Conversions listed
above:
Conversion 1:
I converted the file using flirt.
Distressing, however is that when I check the data range I see this:
avwstats tstat1.img -r
-1.554848 1.625723
tstat1_highres.img -r
-0.845122 0.922256
avwstats tstat1.img -R
-4.851428 4.815962
avwstats tstat1_highres.img -R
-4.145343 4.230853
The means are even slightly off (meaned using -M). This is rather
distressing to me, but is it simply just a natural function of
interpolation ?
When I try outputing 16 bit short images from flirt (adding "-datatype
short" to the command line syntax) the range becomes even worse off
(+/- 4.000000 ) and the files don'e even qualitatively look similar.
Conversion 2:
Is there a quick, easy way to convert between 32-bit and 16-bit analyze
images ?
I have tried a few different methods with varying results. The easiest
method I've found is to use imgcon with this syntax:
imgcon -short <filename.hdr>
But the problem with that is that the values get scaled funny.
Qualitatively, the 16-bit images look the same as their 32-bit parent,
but the values are all wrong.
The resampled img had this range:
avwstats tstat1_highres_16.img -R
-32767.000000 32766.000000
Is there a way to get imgcon to rescale the data correctly, because I
do like the simplicity and speed of the program. Or is there a better,
more reliable way to do this?
Any thoughts ?
-Vikas
****
Vikas Rao
Lab Assistant
[log in to unmask]
Clinical Neuroscience Lab, UCLA
www.cannonlab.net
310-794-9673
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