PSD_FIESTA3D

[romainVala]

Hello

I was interested to simulate the banding artefact for different phase cycling of th bSSFp sequence.
So I play a little bit with the phase increment (CV3)
I first test on the GM/WM/CSF phantome, with one uniform coil, uniform B0.
with the default phase (2*pi/2) the image looks ok, but when I put a RF phase increment (CV3 = 0) I get a big aliasing (in the phase encoding direction) only for the csf compartment.
I do not expect such an artifact ...
Any idea where it may come from ?

Many thanks

Romain

[leoliuf]

Can you provide the screenshot to help diagnosis? When you mentioned one uniform coil and uniform B0, did you mean you used additional coil and mag for the simulation?

[romainVala]

Hello, thanks for your prompt reply, I did not find how to put a screen shot in the web interface So I did not select any coil neither B0, so it takes the default. I only select the GM/WM/CSF phantome and the PSD_FIESTA3D sequence, with the CV3 at pi I get the first attached figure but with the CV3 = 0 I get the warping (only for CSF) (second attach file) Many thanks Romain

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On 04/07/2017 05:38 PM, Fang Liu wrote: Can you provide the screenshot to help diagnosis? When you mentioned one uniform coil and uniform B0, did you mean you used additional coil and mag for the simulation? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFWhuj8qRS10nzzYFd8hGBFNq3DY_86Cks5rtliAgaJpZM4M3Cpo>.

[leoliuf]

Try to use smaller FlipAng and larger DP_Num (more dummy TR section). The artifact is caused by the transient steady-state signal from CSF. You can use SpinWatcher to check MR signal from individual voxel.

[romainVala]

ok, I will have a look, but I do not understand why his is dependent of the RF phase.

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On 04/11/2017 02:58 AM, Fang Liu wrote: Try to use smaller FlipAng and larger DP_Num (more dummy TR section). The artifact is caused by the transient steady-state signal from CSF. You can use SpinWatcher to check MR signal from individual voxel. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFWhusJxPApvUlU8pKtz0qrC8zvB018iks5rutA8gaJpZM4M3Cpo>.

[romainVala]

Hi
I notice a bug when I put a DP_Num greater than 700 (for 8 slices)
it stop ate TR Counts = 640 or 700 (number of TR without dummy scan) and complains about wrong dimension.
Strange because it works ok for smaller DP_NUM

Thanks

Romain

[leoliuf]

Yes, I noticed that too. I will possibly change the limitation of DP_Num to any number in the future version. So far, the DP_Num must be smaller than total phase encoding steps.