I am trying to model light propagation within biological tissues using COMSOL classical PDEs (Helmholtz Equation). I have read several related papers. However, when I finished my own modeling according to the the papers, the result (fluence rate along a line on the surface - reflectance) was of great difference with that obtained from Monte Carlo method. Then I changed the actual light beam with finite size to a point light source within the tissue located at one mean free path, and set the geometry as 3D model, the outcome seems reasonable. But for 3D modeling, it takes more time. So I want to simply the 3D model to a 2D Axi-symmetric model. Theoretically the results should be the same. However, they are not. They differs a lot! I do not know the reason. So could anybody help me with it? That will be greatly appreciated!
The attached are the 3D and 2D-axisymmetric models and related references. By the way, could anyone also check why I can't get reasonable results with the actual beam， as done in the reference? Thank you so much. (Only the result of the "Below point source-3D" model is reasonable, which can be used for comparison.)
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All the Best Your Hainz
Dear Hans, I don't quite understand your answer. Could you please explain it in more details?
Dear Colleague As urologist i worked since 1988 until my retirement with 1026nm and later 980nm Lasers. If You wnat more information about this work i need Your e-mail,adress, than i can send to You where i told this and where we stand today in urology. All the Best Your Hainz [email protected]
In this world i didn't work. Excuse me - but i have learned where i should read alittle bit more Your Hainz
Thank you Takashi. But I think the 3D mode can be simplified to a 2D-axisymmetric model if the 3D model is axisymmetric. In my case, the 3D model is axisymmetric. And in the references, most models were developed with 2D-axisymmetric geometry. By the way, do you recognize any problem about modeling the actual light beam with finite size? Thank you and look forward to your reply.
Thank you Hans. Could you please be more specific about the problems I put forward? I don's quite understand your description. Thank you.
Thank you so much Takashi. As your opinion, the 3D model can not be simplified as a 2D-axisymmetric model. That's fine for me. The only disadvantage of 3D geometry is longer time is needed for computation.
By the way, has your ever done some work with finite element method? Thank you.
I do agree to Takashi Hira about the difference in results caused due to consideration of 3D and 2D. However, you can also take a look at the publication of paper and book of Jaques and Wang how they did the MonteCarlo simulation of light passing through a tissue. Their work is quite informative. We carried out our simulation work and got appreciable result.
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