[Mristudio-users] checkered artifact

[susumu mori]

Hi Mark,

Unfortunately, this is a typical artifact we see in many EPI/DTI data. I
think it's a truncation error, but not sure. If it is a truncation error, it
may decrease by making the image matrix larger, but it causes loss of SNR
and larger deformation. So you win some and lose some. I personally like to
use a smaller matrix (use only the echoes with enough SNR) and take the
artifacts as part of the game....

On Thu, Aug 4, 2011 at 3:16 PM, Mark A. Pinsk <mpinsk at gmail.com> wrote:

> Hi everyone,
>
> We're seeing an artifact in our DTI images (most visible in the non-DWI
> images, but they show up everywhere including the calculated FA maps).  I
> assume this will negatively impact any tracking analyses.   It's a checkered
> pattern that originates from high intensity regions (i.e. ventricles) and
> goes in both the frequency and the phase encode directions.  Links to
> snapshots below.   I was told by one person that they are Fourier truncation
> artifacts, but I was also told by another person that they are flow
> artifacts.
>
> Can someone clarify for me (1) what they are, (2) should I be concerned,
> and (3) how do I avoid them ?
>
> http://dl.dropbox.com/u/3889124/dti_snapshot1.tiff
> http://dl.dropbox.com/u/3889124/dti_snapshot2.tiff
>
> Thanks very much!
> Mark
>
>
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