[Mristudio-users] effect of TE on FA

[Susumu Mori]

Hi Mark,

For simulation study, Daniel Alexander has a paper describing the impact of
TE and various image parameters.

Practically, only the measurements can give us the best information but it
is possible the results are compounded by physiological noise unless the
impact of the TE is large.

Theoretically, the largest influence could be the SNR decrease. As Dorian
mentioned, there are papers describing the effect of SNR, including ours.
As TE gets longer, the SNR goes down and FA goes up. If you have a high SNR
(e.g. long scan time, lower resolution), a certain amount of the SNR
decrease doesn't cause FA increase, but if the SNR is low to begin with,
you would see more impact of SNR change.

I think the reason you don't fine many papers about the TE impact is;
> The results are predictable; longer TE, lower SNR, higher FA
> The results depends on the exact image parameters (magnetic field
strength, scanning time, TE, b-value, etc) and thus the results do not have
general importance.

Susumu


On Thu, May 15, 2014 at 5:54 PM, Mark Wagshul
<Mark.Wagshul at einstein.yu.edu>wrote:

>  Does anyone have data on this?  I have been able to find a limited
> number of papers.  There is a reference to a “dataset #4” of DTI data with
> varying TE’s on the mBIRN site but I can’t find the data on the site.  We
> have a pretty large dataset from over 60 relatively normal individuals
> (minimal to very mild TBI) with two DTI datasets at different TE’s (65 vs.
> 84ms, same b-value) which seem to be showing the opposite effect from what
> we would expecting (FA is decreasing with TE, since the diffusion times are
> longer with the longer TE set, we would expect FA to increase).  I would
> appreciate comments, or like to know if anyone has any good data on these
> effects.  Thanks,
>
>
>
> Mark
>
>
>
> _______________
>
> Mark Wagshul, PhD
> Associate Professor
> Gruss Magnetic Resonance Research Center
> Albert Einstein College of Medicine
> Bronx, NY 10461
> Ph: 718-430-4011
> Email: mark.wagshul at einstein.yu.edu
>
>
>
> [image: Einstein_LogoTagA_Blue_RGB]
>
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