Fast Electromagnetic Analysis of MRI Transmit RF Coils Based on Accelerated Integral Equation Methods

Abstract

A fast frequency domain full-wave electromagnetic simulation method is introduced for the analysis of MRI coils loaded with the realistic human body models. The approach is based on integral equation methods decomposed into two domains: 1) the RF coil array and shield, and 2) the human body region where the load is placed. The analysis of multiple coil designs is accelerated by introducing the precomputed magnetic resonance Green functions (MRGFs), which describe how the particular body model used responds to the incident fields from external sources. These MRGFs, which are precomputed once for a given body model, can be combined with any integral equation solver and reused for the analysis of many coil designs. This approach provides a fast, yet comprehensive, analysis of coil designs, including the port S-parameters and the electromagnetic field distribution within the inhomogeneous body. The method solves the full-wave electromagnetic problem for a head array in few minutes, achieving a speed up of over 150 folds with root mean square errors in the electromagnetic field maps smaller than 0.4% when compared to the unaccelerated integral equation-based solver. This enables the characterization of a large number of RF coil designs in a reasonable time, which is a first step toward an automatic optimization of multiple parameters in the design of transmit arrays, as illustrated in this paper, but also receive arrays.

The ultimate intrinsic signal‐to‐noise ratio of loop‐ and dipole‐like current patterns in a realistic human head model

“…With the help of polarization currents (J), Equation can be reformulated as a volume integral equation (VIE), abbreviated with JVIE. Recently, a fast FFT‐based volume integral equation method was published to efficiently solve the JVIE‐problem . The authors distribute their code named “MARIE” under https://github.com/thanospol/MARIE.…”

An analytic expression for the ultimate intrinsic SNR in a uniform sphere

“…Recently, a novel approach based on volume integral equations (VIE) has been proposed to calculate the UISNR in a realistic head model . Although relatively rapid, the VIE‐based calculations require a graphics processing unit (GPU) to handle the ultimate basis set, as well as proficiency with the MARIE (magnetic resonance integral equation suite) open source software . Furthermore, the results described in Guerin et al suggest that a uniform sphere with average brain electrical properties is a good approximation of a human head for UISNR calculations.…”

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Accelerated domain decomposition FEM-BEM solver for magnetic resonance imaging (MRI) via discrete empirical interpolation method

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