Comptes Rendus
Radio science for connecting humans with information systems / L'homme connecté
A regularised boundary element formulation for contactless SAR evaluations within homogeneous and inhomogeneous head phantoms
Comptes Rendus. Physique, Volume 16 (2015) no. 9, pp. 776-788.

This work presents a Boundary Element Method (BEM) formulation for contactless electromagnetic field assessments. The new scheme is based on a regularised BEM approach that requires the use of electric measurements only. The regularisation is obtained by leveraging on an extension of Calderón techniques to rectangular systems leading to well-conditioned problems independent of the discretisation density. This enables the use of highly discretized Huygens surfaces that can be consequently placed very near to the radiating source. In addition, the new regularised scheme is hybridised with both surfacic homogeneous and volumetric inhomogeneous forward BEM solvers accelerated with fast matrix–vector multiplication schemes. This allows for rapid and effective dosimetric assessments and permits the use of inhomogeneous and realistic head phantoms. Numerical results corroborate the theory and confirms the practical effectiveness of all newly proposed formulations.

Cet article présente une méthode aux éléments de frontière (BEM) adaptée à l'évaluation sans contact du champ électromagnétique. La nouvelle approche est fondée sur une formulation intégrale régularisée, qui nécessite seulement des mesures du champ électrique. La régularisation est obtenue à partir d'une extension des techniques de préconditionnement de type Calderón aux matrices rectangulaires. Cela résulte en des systèmes bien conditionnés indépendamment de la densité de discrétisation et permet l'utilisation de surfaces de Huygens ayant une discrétisation très fine qui, par voie de conséquence, peuvent être placées très près de la source rayonnante. En outre, la nouvelle formulation est hybridée avec deux solveurs d'intégrales de surface (pour des problèmes homogènes) et de volume (pour des problèmes non homogènes) et est accélérée avec des algorithmes rapides de multiplication matrice–vecteur. Ceci permet des évaluations dosimétriques rapides et efficaces et permet aussi l'utilisation de fantômes de tête non homogènes et réalistes. Les résultats numériques corroborent la théorie et confirment l'efficacité pratique de toutes les nouvelles formulations proposées.

Published online:
DOI: 10.1016/j.crhy.2015.10.003
Keywords: Computational dosimetry, SAR assessments, Boundary Element Method, Calderón preconditioning
Mot clés : Dosimétrie computationnelle, Evaluations SAR, Méthode des élements de frontière, Préconditionnement de Calderón

Rajendra Mitharwal 1; Francesco P. Andriulli 1

1 Computational Electromagnetics Research Laboratory, Microwave Department, Télécom Bretagne, Brest, France
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Rajendra Mitharwal; Francesco P. Andriulli. A regularised boundary element formulation for contactless SAR evaluations within homogeneous and inhomogeneous head phantoms. Comptes Rendus. Physique, Volume 16 (2015) no. 9, pp. 776-788. doi : 10.1016/j.crhy.2015.10.003. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2015.10.003/

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