1,721,031 research outputs found
Near-field electromagnetic cloaking of metallic elongated implants to reduce RF-inhomogeneity artifacts and SAR elevation
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Contrast source inversion global Maxwell tomography: a technique for electric properties MR imaging without phase information
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A fast tool for the parametric analysis of human body exposed to LF electromagnetic fields in biomedical applications
Full text linkA numerical procedure for analyzing electromagnetic (EM) fields interactions with biological tissues is presented. The proposed approach aims at drastically reducing the computational burden required by the repeated solution of large scale problems involving the interaction of the human body with EM fields, such as in the study of the time evolution of EM fields, uncertainty quantification, and inverse problems. The proposed volume integral equation (VIE), focused on low frequency applications, is a system of integral equations in terms of current density and scalar potential in the biological tissues excited by EM fields and/or electrodes connected to the human body. The proposed formulation requires the voxelization of the human body and takes advantage of the regularity of such discretization by speeding-up the computational procedure. Moreover, it exploits recent advancements in the solution of VIE by means of iterative preconditioned solvers and ad hoc parametric Model Order Reduction techniques. The efficiency of the proposed tool is demonstrated by applying it to a couple of realistic model problems: the assessment of the peripheral nerve stimulation, performed in terms of evaluation of the induced electric field, due to the gradient coils of a magnetic resonance imaging scanner during a clinical examination and the assessment of the exposure to environmental fields at 50 Hz of live-line workers with uncertain properties of the biological tissues. Thanks to the proposed method, uncertainty quantification analyses and time domain simulations are possible even for large scale problems and they can be performed on standard computers and reasonable computation time. Sample implementation of the method is made publicly available at https://github.com/UniPD-DII-ETCOMP/BioMOR
3D GPU-based implementation of the contrast source inversion for breast lesion detection
Full text linkIn microwave tomography, applying a proper inversion method to the measured data may result in quantitative imaging of the electrical properties (EPs) at the frequencies of the used electromagnetic radiation. Some physiopathological statuses of the breast tissue can be distinguished based on the estimated EPs [1]. A previous approach presented in [2] reports preliminary results obtained with a two-dimensional implementation of the Contrast Source Inversion (CSI) method [3] applied to simulated data. This work aims to discuss the transition to a 3D algorithm. Some optimization techniques in the MATLAB environment have been applied to the 2D version to reduce time consumption, which becomes a predominant variable with 3D data. Namely, computationally expensive operations on large data have been transferred to GPU (NVIDIA A 100 80 GB). This leads to an advantage especially for the FFT, which is performed in every iterative step. The efforts have permitted to reduce the execution time of each iterative step, reaching a speed-up factor of about 25 with respect to the CPU (Intel Xeon Gold 6430 2.10 GHz 512 GB RAM) version of the code. To obtain preliminary results about the feasibility of the 3D imaging method for detecting dielectric properties, a virtual experiment was performed. The transmit-receive setup is composed of a transmitting antenna that assumes ten equidistant positions around a cylindrical phantom, and a receiving antenna assuming forty equidistant positions around it. A heterogeneous phantom was considered, with electrical properties that emulate the ones of a healthy breast (σ = 0.1 and εr = 4), and a longitudinal cylindrical inclusion (r = 1 cm), whose high electrical properties simulate those of a breast lesion (σ = 1 and εr = 15). The incident electric field was obtained through the simulation of a Hom antenna fed at the frequency of 5 GHz, performed in Sim4Life. Total electric fields were computed in the receiving antennas’ locations and a homogeneous initial guess (σ = 0.01 and εr = 3) was adopted. An additive regularization in the CSI cost functional was introduced to overcome the image artifacts induced by the ill-posedness of the inverse scattering problem. Figure 1 provides results obtained after 3,000 iterations of CSI (about 2.5 hours of execution)
Subject Specific Brain SAR Maps Based on B1+ with CR-EPT Derived Electrical Conductivity
No full textEffect of tissue parameters on skin heating due to millimeter em waves
No full textThis paper investigates the influence of electrical and thermal human tissue parameters on the heating of a body illuminated by a millimeter plane electromagnetic wave. A stochastic approach is considered with a three-layer model of the body: it is found that the parameters of skin play a major role
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