This is a bug in FSLView and or DTIFIT that results from the cal_max and
cal_min tags of the FA NIFTI header being improperly set. FSLView ignores
user settings of max and min when modulating color FA, so you must set the
tags correctly. You can do this by opening the file header with fsledithd
and changing cal_max = '1' and cal_min = '0' as would be correct for an FA
image.
Hopefully there is some solution to this in the next FSL version :)
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Anastasia Ford
Sent: Thursday, July 10, 2008 1:02 PM
To: [log in to unmask]
Subject: [FSL] Averaging using fslmaths
Hi,
I have two diffusion datasets collected from the same subject back to back
and I would like to average the two datasets to decrease the noise.
I use FLIRT to register one scan to the other and then fslmaths to add the
two data sets (fslmaths data_a -add data_b data_sum) and then divide by 2
(fslmaths data_sum -div 2 data_average). Then I fit the tensors and I am
having trouble viewing the FA map overlaid with V1. When I modulate V1 to FA
the image disappears. I have tried to use different max/min display
intensities for FA, but none of them work. Do you have any suggestions?
Sincerely,
Anastasia
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