ghost artifact in GRE simulation

[Hu Cheng]

Hi, 

First thank the developer for this nice tool. I'm interested in investigating the noise behavior from simulation. However, when I ran the simulation on the 2D sphere phantom using the GRE sequence, the reconstructed image suffered severe ghost artifact. I don't know if this is due to the simulation or the NUFFT recon. It's normal to see this kind of artifact in the EPI image but this one in GRE is even larger. Am I missing anything? I use the 2.90 version on both windows and linux. 

Thanks!

Hu

[Lars G. Hanson]

Dear Hu,
Good that your problem was solved. A somewhat general solution is to
start simulating with low density and ignore artifacts. When your
sequence seems to work, you can increase the density, and keep doing
that until your results have converged. Only then can you trust your
results.
Kind regards,
Lars

On 9/1/23 5:24 PM, Hu Cheng wrote:
> Hi Lars,
>
> Yes, you are correct! I changed the density to 0.5 and the artifact
was gone. Interesting.
> Thank you very much!
>
> Hu
>
> On Fri, Sep 1, 2023 at 4:03 AM Lars G. Hanson <la...@drcmr.dk> wrote:
>
>     Is your spin density high enough to avoid simulation artifacts
(errors
>     resulting from imperfect simulation)? Maybe try 0.1 mm for dx,dy
in the
>     screen you showed.
>     Kind regards,
>     Lars

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