On 19 Oct 2006, at 05:55, Hedok Lee wrote:

Dear FSLers.

My apology for being slightly off the topic.

I’m writing regarding a quality assurance of DWI images in DTI(b=0 and 

b=1000) sequence.  We’ve been collecting DTI along 25 directions+1 b0 with 

26 slices(1mmx1mmx5mm) in each volume (676 images total) using GE 1.5T.  We 

recently observed relatively high FA in one slice compare to the adjacent 

slices, so I began looking at individual images.  It turns out this is due 

to a few slices of almost no signal in DWI.  After checking 676 slices, I 

was wondering if there is criteria, or diagnostic tool, to detect bad 

slices.  Really high, or low, intensity DWIs are easy to detect.  Some of 

the slices look suspicious but I don’t have enough experience to tell 

whether it’s good or bad.  I appreciate if someone has an experience, or a 

tool, to set a criteria on this.  How do people trust what they get from 

DTI is of decent quality?  

More specific questions are

Within the same volume, do mean intensity over slices supposed to be 

close?  If so, what’s the reasonable standard deviation.  How about the 

mean intensities of volumes over different diffusion gradients.

Basically, I ‘m trying to write a simple script to detect bad slices so 

that I don’t have to eyeball 676 images every time.  If there is a script 

for this, please let me know.

Thanks,

Hedok