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How to understand the asymmetry of B1 on XY plane in Tutorial: MRI Loop Coil

Posted: Mon 23 Aug 2021, 08:38
by chzhao123
Hi Dr. Liebig,

Thanks for the excellent toolbox for EM simulation. I'm trying to play with some tutorials provided on the website. When I was reading Tutorial: MRI Loop Coil, I noticed that the B1+ and B1- on XY plane are not symmetric. The asymmetry may be not due to the medium placed in the space since replacing the human phantom with a spherical phantom cannot remove such asymmetric B1 fields (see attached figure). Do you have any ideas? Thank you!

Best,
Chenyang
WeChat Image_20210822233838.png
WeChat Image_20210822233838.png (61.95 KiB) Viewed 1280 times

Re: How to understand the asymmetry of B1 on XY plane in Tutorial: MRI Loop Coil

Posted: Thu 02 Sep 2021, 20:03
by thorsten
Hi,

I agree it should not be asymmetric. You used an unmodified Tutorial?
If I find the time I will have a closer look. Let me know if you have learned anything new in the meantime.

regards
Thorsten

Re: How to understand the asymmetry of B1 on XY plane in Tutorial: MRI Loop Coil

Posted: Mon 06 Sep 2021, 21:33
by rml
Hi,
I did a quick search. This paper, for example, is freely available:
https://mriquestions.com/uploads/3/4/5/ ... vs_b1-.pdf
You could define the spherical phantom as air-filled for a test. Then the asymmetry should disappear.
And if that works, you should be able to replicate the results shown in the paper.
But please don't forget that the mesh has to be finer at higher epsR.