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

How to use openEMS. Discussion on examples, tutorials etc

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chzhao123
Posts: 1
Joined: Mon 23 Aug 2021, 08:22

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

Post by chzhao123 » Mon 23 Aug 2021, 08:38

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
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thorsten
Posts: 1475
Joined: Mon 27 Jun 2011, 12:26

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

Post by thorsten » Thu 02 Sep 2021, 20:03

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

rml
Posts: 19
Joined: Fri 17 Aug 2012, 14:18

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

Post by rml » Mon 06 Sep 2021, 21:33

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.

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