Finite Element Modeling of scattered electromagnetic waves for stroke analysis

Priyadarshini, Neha; Rajkumar, E

doi:10.1109/embc.2013.6610023

Cited by 8 publications

(16 citation statements)

References 12 publications

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“…However, in this study the incorporated frequency-dependent closed-form models are evaluated at 1 GHz only. This is because 1 GHz is the most appropriate frequency for a MW head-imaging system, suggested by the previously referenced literature [ 14 , 23 , 25 , 27 , 35 , 38 , 40 , 42 ] and the evaluations we made during our research [ 43 – 45 ]. This frequency allows a good penetration of MW signals into a human head, while providing a reasonable spatial resolution of brain images.…”

Section: Methodsmentioning

confidence: 93%

“…Two types of stroke were differentiated through a statistical classifier algorithm. Priyadarshini and Rajkumar [ 27 ] applied a FEM–CSI methodology on a four-layered ellipsoid head model to explore the MW scattering phenomenon for brain stroke detection of both types. The head model was surrounded by an array of eight dipole antennae, each operating in multi-static mode at the 1 GHz frequency.…”

Section: Introductionmentioning

confidence: 99%

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Finite-element analysis of microwave scattering from a three-dimensional human head model for brain stroke detection

2018

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In this paper, a detailed analysis of microwave (MW) scattering from a three-dimensional (3D) anthropomorphic human head model is presented. It is the first time that the finite-element method (FEM) has been deployed to study the MW scattering phenomenon of a 3D realistic head model for brain stroke detection. A major contribution of this paper is to add anatomically more realistic details to the human head model compared with the literature available to date. Using the MRI database, a 3D numerical head model was developed and segmented into 21 different types through a novel tissue-mapping scheme and a mixed-model approach. The heterogeneous and frequency-dispersive dielectric properties were assigned to brain tissues using the same mapping technique. To mimic the simulation set-up, an eight-elements antenna array around the head model was designed using dipole antennae. Two types of brain stroke (haemorrhagic and ischaemic) at various locations inside the head model were then analysed for possible detection and classification. The transmitted and backscattered signals were calculated by finding out the solution of the Helmholtz wave equation in the frequency domain using the FEM. FE mesh convergence analysis for electric field values and comparison between different types of iterative solver were also performed to obtain error-free results in minimal computational time. At the end, specific absorption rate analysis was conducted to examine the ionization effects of MW signals to a 3D human head model. Through computer simulations, it is foreseen that MW imaging may efficiently be exploited to locate and differentiate two types of brain stroke by detecting abnormal tissues’ dielectric properties. A significant contrast between electric field values of the normal and stroke-affected brain tissues was observed at the stroke location. This is a step towards generating MW scattering information for the development of an efficient image reconstruction algorithm.

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Section: Methodsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Finite-element analysis of microwave scattering from a three-dimensional human head model for brain stroke detection

2018

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“…In the same year, ( Priyadarshini & Rajkumar, 2013 ) performed computer simulations to study the electromagnetic (EM) waves scattering phenomenon by an ellipsoid head model for brain stroke analysis. The head model comprising four-layers of brain tissue with an emulated sphere shaped stroke of both types was utilized.…”

Section: Introductionmentioning

confidence: 99%

Levels of detail analysis of microwave scattering from human head models for brain stroke detection

Qureshi¹,

Mustansar²

2017

PeerJ

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In this paper, we have presented a microwave scattering analysis from multiple human head models. This study incorporates different levels of detail in the human head models and its effect on microwave scattering phenomenon. Two levels of detail are taken into account; (i) Simplified ellipse shaped head model (ii) Anatomically realistic head model, implemented using 2-D geometry. In addition, heterogenic and frequency-dispersive behavior of the brain tissues has also been incorporated in our head models. It is identified during this study that the microwave scattering phenomenon changes significantly once the complexity of head model is increased by incorporating more details using magnetic resonance imaging database. It is also found out that the microwave scattering results match in both types of head model (i.e., geometrically simple and anatomically realistic), once the measurements are made in the structurally simplified regions. However, the results diverge considerably in the complex areas of brain due to the arbitrary shape interface of tissue layers in the anatomically realistic head model.After incorporating various levels of detail, the solution of subject microwave scattering problem and the measurement of transmitted and backscattered signals were obtained using finite element method. Mesh convergence analysis was also performed to achieve error free results with a minimum number of mesh elements and a lesser degree of freedom in the fast computational time. The results were promising and the E-Field values converged for both simple and complex geometrical models. However, the E-Field difference between both types of head model at the same reference point differentiated a lot in terms of magnitude. At complex location, a high difference value of 0.04236 V/m was measured compared to the simple location, where it turned out to be 0.00197 V/m. This study also contributes to provide a comparison analysis between the direct and iterative solvers so as to find out the solution of subject microwave scattering problem in a minimum computational time along with memory resources requirement.It is seen from this study that the microwave imaging may effectively be utilized for the detection, localization and differentiation of different types of brain stroke. The simulation results verified that the microwave imaging can be efficiently exploited to study the significant contrast between electric field values of the normal and abnormal brain tissues for the investigation of brain anomalies. In the end, a specific absorption rate analysis was carried out to compare the ionizing effects of microwave signals to different types of head model using a factor of safety for brain tissues. It is also suggested after careful study of various inversion methods in practice for microwave head imaging, that the contrast source inversion method may be more suitable and computationally efficient for such problems.

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“…The methodology was respectively based on the comparison of reflection coefficients (S 11 ) or reflection phases of any pair of antennas located symmetrically around the head. In the same year, Priyadarshini and Rajkumar [25] performed an EM waves scattering analysis for brain stroke diagnostics using FEM-CSI methodology but on a simplified ellipsoid head model.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Microwave Scattering From a Realistic Human Head Model for Brain Stroke Detection Using Electromagnetic Impedance Tomography

Qureshi¹,

Mustansar²,

Maqsood³

2016

PIER M

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Brain stroke incidences have arisen at an alarming rate over the past few decades. These strokes are not only life threatening, but also bring with them a very poor prognosis. There is a need to investigate the onset of stroke symptoms in a matter of few hours by the doctor. To address this, Electromagnetic Impedance Tomography (EMIT) employing microwave imaging technique is an emerging, cost-effective and portable brain stroke diagnostic modality. It has the potential for rapid stroke detection, classification and continuous brain monitoring. EMIT can supplement current brain imaging and diagnostic tools (CT, MRI or PET) due to its safe, non-ionizing and non-invasive features. It relies on the significant contrast between dielectric properties of the normal and abnormal brain tissues. In this paper, a comparison of microwave signals scattering from an anatomically realistic human head model in the presence and absence of brain stroke is presented. The head model also incorporates the heterogenic and frequency-dispersive behavior of brain tissues for the simulation setup. To study the interaction between microwave signals and the multilayer structure of head, a forward model has been formulated and evaluated using Finite Element Method (FEM). Specific Absorption Rate (SAR) analysis is also performed to comply with safety limits of the transmitted signals for minimum ionizing effects to brain tissues, while ensuring maximum signal penetration into the head.

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Finite Element Modeling of scattered electromagnetic waves for stroke analysis

Cited by 8 publications

References 12 publications

Finite-element analysis of microwave scattering from a three-dimensional human head model for brain stroke detection

Finite-element analysis of microwave scattering from a three-dimensional human head model for brain stroke detection

Levels of detail analysis of microwave scattering from human head models for brain stroke detection

Analysis of Microwave Scattering From a Realistic Human Head Model for Brain Stroke Detection Using Electromagnetic Impedance Tomography

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