Tel : +33 4 92 38 77 49
Stéphane Lantéri Tel : +33 4 92 38 77 34 e-mail: <Stephane.Lanteri@sophia.inria.fr>
Biological effects of mobile phone radiation radiation have been investigated both from the experimental and numerical viewpoints. Concerning numerical modeling, the power absorption in a user head is computed using discretized models built from clinical MRI (Magnetic Resonance Images) data. The great majority of such numerical studies have been conducted using the Finite Difference Time Domain (FDTD) method which is based on structured (catesian) meshes for solving the Maxwell equations. Due to the possible straightforward implementation of the algorithm and the availability of computational power, FDTD is currently the leading method for numerical assessment of human exposure to electromagnetic waves. However, the FDTD method still suffers from limitations. Most of those limitations come from the use of rectilinear uniform grids which, within reasonable size, fail to modelize very detailed structures of head tissues that may be essential for reliable compliance testing. So far, little attention has been put to the application of numerical methods able to deal with unstructured meshes that is, FETD Finite Element Time Domain) and FVTD (Finite Volume Time DomainD) methods.
Unstructured mesh based numerical methods were at the heart of the HeadExp cooperative research action of INRIA, that started on January 2003 for a duration of 2 years. This project aimed at filling the gap between medical images of the head and the efficient and accurate numerical modeling of the interaction of electromagnetic waves emitted by mobile phones with biological tissues. This has required the development of specific image analysis tools and automated unstructured mesh generation tools for the construction of realistic discretized human head models based on unstructured, locally refined, tetrahedral meshes. For this purpose, the HeadExp project involved specialists of medical image processing, geometrical modeling and numerical modeling. The Caiman and Geometrica project-teams have taken part to the HeadExp project
The accomplishments of the HeadExp project [scarella-etal:05] have clearly demonstrated the benefits of using unstructured mesh based numerical methods for numerical dosimetry studies of electromagnetic waves. However they have also raised a number of issues that motivate further investigations especially for what concern the construction of geometrical models. In particular, two points deserve attention: a) the simultaneous generation of surfacic (triangular) and volumic (tetrahedral) meshes for several tissues (e.g skin, external and internal skull, brain, etc.) with different resolutions. b) the local refinment of volumic meshes.
This subject proposes to run further investigations on unstructured mesh
generation from medical imaging data. The goal would be in a first step to
improve the numerical models of the head obtained in the HeadExp project and
then to obtain reliable numerical models of the whole human body taking into
account different tissues. Those studies will be perform using the mesh
generation tool provided by the library CGAL. Based on Delaunay refinement,
this unstructed mesh generation tool offers wide possibilities for the
handling of several surfaces in the volume to be meshed and the respect of non
uniform sizing field [oudot-etal:05]. The tool is able to work on three
dimensional images resulting from medical imaging data. This tool is a
powerfull, recently developped tool and its use in such a project would
contribute to its final tuning.
Mariette Yvinec Last modified: Thu Mar 2 09:21:53 CET 2006