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SAR plots of the brain, No results

Posted Feb 11, 2016, 12:27 p.m. EST 8 Replies

Shailesh Joshi
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Hi all,

I was going through the tutorial for Absorbed radiation (SAR) in human brain

www.comsol.com/model/absorbed-radiation-sar-in-the-human-brain-2190

I am not sure if anyone else tried this one but I am struggling to gather results for both the SAR distribution and heating. The only change I did to the model and the instructions provided in the link above was the lumped port setup as suggested by Edgar here:

www.comsol.com/community/forums/general/thread/20391/

I have attached the project file (not computed version as it was too big to attach) and the pictures of the results which show no interaction with the study. It seems that I am missing out on something. Can anyone suggest some pathway on this please?

Thanks very much


8 Replies Last Post May 24, 2016, 10:18 a.m. EDT
Shailesh Joshi
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Posted: 8 years ago Feb 15, 2016, 4:59 a.m. EST
Anybody out there to help?

Thanks
Anybody out there to help? Thanks
Mihai Campean
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Posted: 8 years ago May 18, 2016, 4:30 p.m. EDT
Did you manage to find any solution? I am having the same issue.
Did you manage to find any solution? I am having the same issue.
Shailesh Joshi
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Posted: 8 years ago May 19, 2016, 4:21 a.m. EDT
Mihai

Nope, I gave up on it for a moment. This thread does not seem to attract the experts :(
Mihai Nope, I gave up on it for a moment. This thread does not seem to attract the experts :(
Mihai Campean
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Posted: 8 years ago May 19, 2016, 4:45 a.m. EDT
I will try again today after I get out from work. Maybe I can find a solution. I found a video on YouTube that does exactly this stuff and it works for him. This is the video : youtu.be/3It9CpuXjpI. Maybe you want to give it a look.
I will try again today after I get out from work. Maybe I can find a solution. I found a video on YouTube that does exactly this stuff and it works for him. This is the video : https://youtu.be/3It9CpuXjpI. Maybe you want to give it a look.
Magnus Olsson COMSOL Employee

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Posted: 8 years ago May 19, 2016, 5:10 a.m. EDT
Hi,

The problem is in the settings for the Lumped Port. When you have selected "User defined" for "Type of Lumped port" you must give a nonzero entry for "Direction between lumped port terminals". In your case, you should enter (0,0,1) as the lumped port voltage/current is directed along the z axis.

The "User defined" option is provided for cases when COMSOL cannot deduce, from geometry and boundary settings, how to apply the lumped port excitation. I will file an enhancement request to throw an error when you leave required nonzero fields at their default zero value.

Best regards,
Magnus
Hi, The problem is in the settings for the Lumped Port. When you have selected "User defined" for "Type of Lumped port" you must give a nonzero entry for "Direction between lumped port terminals". In your case, you should enter (0,0,1) as the lumped port voltage/current is directed along the z axis. The "User defined" option is provided for cases when COMSOL cannot deduce, from geometry and boundary settings, how to apply the lumped port excitation. I will file an enhancement request to throw an error when you leave required nonzero fields at their default zero value. Best regards, Magnus
Shailesh Joshi
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Posted: 8 years ago May 19, 2016, 5:39 a.m. EDT
Cheers Magnus, I will give it a go over the weekend
Cheers Magnus, I will give it a go over the weekend
Mihai Campean
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Posted: 8 years ago May 19, 2016, 1:15 p.m. EDT
Thank you Magnus for your solution. I have also a question maybe you can help me.

What parameters I have to modify in order to affect the radiation dose that is absorbed by the human head?

Thank you in advance,
Mihai
Thank you Magnus for your solution. I have also a question maybe you can help me. What parameters I have to modify in order to affect the radiation dose that is absorbed by the human head? Thank you in advance, Mihai
Shailesh Joshi
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Posted: 8 years ago May 24, 2016, 10:18 a.m. EDT
The problem seems to be solved. I changed and used "Lumped port<Uniform<Cable" settings. Also found I had a small error in my geometry.

Anyways thanks very much guys, all is well.

@Mihai, SAR and temperature values depend upon the specific heat and conductivity of the tissue which are inherent properties of the tissue.

Shailesh
The problem seems to be solved. I changed and used "Lumped port

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