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Effective exploitation of the a priori information through a microwave imaging procedure based on the SMW for NDE/NDT applications

TL;DR: This paper presents an innovative microwave technique, which is suitable for the detection of defects in nondestructive-test and nondestructureive-evaluation applications where a lot of a priori information is available, and shows some interesting features by a computational point of view.
Abstract: This paper presents an innovative microwave technique, which is suitable for the detection of defects in nondestructive-test and nondestructive-evaluation (NDT/NDE) applications where a lot of a priori information is available. The proposed approach is based on the equations of the inverse scattering problem, which are solved by means of a minimization procedure based on a genetic algorithm. To reduce the number of problem unknowns, the available a priori information is efficiently exploited by introducing an updating procedure for the electric field computation based on the Sherman-Morrison-Woodbury formula. The results of a representative set of numerical experiments as well as comparisons with state-of-the-art methods are reported. They confirm the effectiveness, feasibility, and robustness of the proposed approach, which shows some interesting features by a computational point of view as well.

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UNIVERSITY
OF TRENTO
DEPARTMENT OF INFORMATION AND COMMUNICATION TECHNOLOGY
38050 Povo – Trento (Italy), Via Sommarive 14
http://www.dit.unitn.it
EFFECTIVE EXPLOITATION OF THE A-PRIORI INFORMATION THROUGH A
MICROWAVE IMAGING PROCEDURE BASED ON THE SMW FOR
NDE/NDT APPLICATIONS
M. Benedetti, M. Donelli, G. Franceschini, M. Pastorino, and
A. Massa
May 2005
Technical Report DIT-05-006

.

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Citations
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Journal ArticleDOI
TL;DR: In this article, an overview of evolutionary algorithms (EAs) as applied to the solution of inverse scattering problems is presented, focusing on the use of different population-based optimization algorithms for the reconstruction of unknown objects embedded in an inaccessible region when illuminated by a set of microwaves.
Abstract: This review is aimed at presenting an overview of evolutionary algorithms (EAs) as applied to the solution of inverse scattering problems. The focus of this work is on the use of different population-based optimization algorithms for the reconstruction of unknown objects embedded in an inaccessible region when illuminated by a set of microwaves. Starting from a general description of the structure of EAs, the classical stochastic operators responsible for the evolution process are described. The extension to hybrid implementations when integrated with local search techniques and the exploitation of the 'domain knowledge', either a priori obtained or collected during the optimization process, are also presented. Some theoretical discussions concerned with the convergence issues and a sensitivity analysis on the parameters influencing the stochastic process are reported as well. Successively, a review on how various researchers have applied or customized different evolutionary approaches to inverse scattering problems is carried out ranging from the shape reconstruction of perfectly conducting objects to the detection of the dielectric properties of unknown scatterers up to applications to sub-surface or biomedical imaging. Finally, open problems and envisaged developments are discussed.

439 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the use of dielectric a priori data in the reconstruction algorithm for microwave tomography and found that the accuracy and ability to resolve small objects can significantly be improved.
Abstract: A study is presented where the use of dielectric a priori data in the reconstruction algorithm for microwave tomography is investigated. A new algorithm has been developed that includes the a priori dielectric data in the reconstruction process. This development is made as an extension to a conventional conjugate-gradient reconstruction algorithm. This paper further contains a numerical study of the new algorithm where the results indicate that by taking the a priori data into account, the accuracy and ability to resolve small objects can significantly be improved. This study was motivated by the development of an application for biomedical microwave imaging where it is investigated how knowledge of the tissue properties being imaged potentially can be used to improve the accuracy in the reconstruction.

68 citations


Cites background from "Effective exploitation of the a pri..."

  • ...This is, for example, viable in biomedical imaging where the organs and tissues can be assumed known [28], or when testing an object for a defect when the unperturbed object otherwise is known [29]....

    [...]

Journal ArticleDOI
TL;DR: A convolutional neural network (CNN)-assisted dielectric imaging method, which uses CNN to incorporate the abundant image information from magnetic resonance (MR) images into the model-based microwave inverse scattering imaging process and generate high-fidelity dielectrics images, is introduced.
Abstract: We introduce a convolutional neural network (CNN)-assisted dielectric imaging method, which uses CNN to incorporate the abundant image information from magnetic resonance (MR) images into the model-based microwave inverse scattering imaging process and generate high-fidelity dielectric images. A CNN is designed and trained to learn the complex mapping function from MR T1 images to dielectric images. Once trained, the new patients’ MR T1 images are fed into the CNN to generate predicted dielectric images, which are used as the starting image for the microwave inverse scattering imaging. The CNN-predicted dielectric image, containing abundant prior information from MR images, significantly reduces the non-linearity and ill-posedness of the inverse scattering problem. We demonstrate the application of the proposed method to recover human brain dielectric images at 4 and 2 mm resolution with single-frequency and multifrequency microwave measurements. The reconstructed brain dielectric images with the proposed method show significant improvements in image quality compared with images reconstructed with no assistance from MR and CNN.

51 citations


Cites methods from "Effective exploitation of the a pri..."

  • ...When the imaging problem is limited to only detecting defects, prior information can be introduced in the electric field computation based on the Sherman–Morrison–Woodbury formula to reduce the number of unknowns [19]....

    [...]

Journal ArticleDOI
TL;DR: A biomedical microwave tomography system with 3D-imaging capabilities has been constructed and translated to the clinic as discussed by the authors, where a modified monopole antenna array (composed of two interwoven eight-element subarrays), in conjunction with an updated motion-control system capable of independently moving the sub-arrays to various in-plane and cross-plane positions within the illumination chamber, has been configured in the new design for full volumetric data acquisition Signal-to-noise ratios (SNRs) are more than adequate for all transmit/receive antenna
Abstract: A biomedical microwave tomography system with 3D-imaging capabilities has been constructed and translated to the clinic Updates to the hardware and reconfiguration of the electronic-network layouts in a more compartmentalized construct have streamlined system packaging Upgrades to the data acquisition and microwave components have increased data-acquisition speeds and improved system performance By incorporating analog-to-digital boards that accommodate the linear amplification and dynamic-range coverage our system requires, a complete set of data (for a fixed array position at a single frequency) is now acquired in 58 s Replacement of key components (eg, switches and power dividers) by devices with improved operational bandwidths has enhanced system response over a wider frequency range High-integrity, low-power signals are routinely measured down to −130 dBm for frequencies ranging from 500 to 2300 MHz Adequate inter-channel isolation has been maintained, and a dynamic range >110 dB has been achieved for the full operating frequency range (500–2900 MHz) For our primary band of interest, the associated measurement deviations are less than 033% and 05° for signal amplitude and phase values, respectively A modified monopole antenna array (composed of two interwoven eight-element sub-arrays), in conjunction with an updated motion-control system capable of independently moving the sub-arrays to various in-plane and cross-plane positions within the illumination chamber, has been configured in the new design for full volumetric data acquisition Signal-to-noise ratios (SNRs) are more than adequate for all transmit/receive antenna pairs over the full frequency range and for the variety of in-plane and cross-plane configurations For proximal receivers, in-plane SNRs greater than 80 dB are observed up to 2900 MHz, while cross-plane SNRs greater than 80 dB are seen for 6 cm sub-array spacing (for frequencies up to 1500 MHz) We demonstrate accurate recovery of 3D dielectric property distributions for breast-like phantoms with tumor inclusions utilizing both the in-plane and new cross-plane data

49 citations

Journal ArticleDOI
TL;DR: A methodological approach for the detection of multiple defects inside dielectric or conductive media using inverse scattering equations solved by means of different optimization strategies and a formulation based on the inhomogeneous Green's function is adopted.
Abstract: We propose a methodological approach for the detection of multiple defects inside dielectric or conductive media. Two innovative algorithms are developed starting from the inverse scattering equations solved by means of different optimization strategies. In the first implementation, a hierarchical strategy based on parallel-subprocesses is considered, whereas the second algorithm employs a single-process architecture. Whatever the implementation, the arising cost function is minimized through a suitable hybrid-coded genetic algorithm, whose individuals encode the problem unknowns. In order to achieve a computational saving, the formulation based on the inhomogeneous Green's function is adopted and each crack-region is parametrized by means of a selected set of descriptive parameters. The approach as well as its different implementations are assessed through a selected set of numerical experiments and in comparison with previously developed single-crack inverse scattering methods

49 citations


Cites background from "Effective exploitation of the a pri..."

  • ...Such a topic has been effectively addressed in [19]–[21]....

    [...]

References
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Book
01 Sep 1988
TL;DR: In this article, the authors present the computer techniques, mathematical tools, and research results that will enable both students and practitioners to apply genetic algorithms to problems in many fields, including computer programming and mathematics.
Abstract: From the Publisher: This book brings together - in an informal and tutorial fashion - the computer techniques, mathematical tools, and research results that will enable both students and practitioners to apply genetic algorithms to problems in many fields Major concepts are illustrated with running examples, and major algorithms are illustrated by Pascal computer programs No prior knowledge of GAs or genetics is assumed, and only a minimum of computer programming and mathematics background is required

52,797 citations

Journal ArticleDOI
TL;DR: The theory and equations for the scattering pattern of a dielectric cylinder of arbitrary cross-section shape were developed in this paper, where the harmonic incident wave was assumed to have its electric vector parallel with the axis of the cylinder, and the field intensities were assumed to be independent of distance along the axis.
Abstract: The theory and equations are developed for the scattering pattern of a dielectric cylinder of arbitrary cross section shape. The harmonic incident wave is assumed to have its electric vector parallel with the axis of the cylinder, and the field intensities are assumed to be independent of distance along the axis. Solutions are readily obtained for inhomogeneous cylinders when the permittivity is independent of distance along the cylinder axis. Although other investigators have approximated the field within the dielectric body by the incident field, we treat the total field as an unknown function which is determined by solving a system of linear equations. In the case of the dielectric cylindrical shell of circular cross section, this technique yields results which agree accurately with the exact classical solution. Scattering patterns are also presented in graphical form for a dielectric shell of semicircular cross section, a thin homogeneous plane dielectric sheet of finite width, and an inhomogeneous plane sheet. The effects of surface-wave excitation and mutual interaction among the various portions of the dielectric shell are included automatically in this solutiom

1,000 citations


"Effective exploitation of the a pri..." refers methods in this paper

  • ...Thus, by considering the point-matching version of the method of moment [6], and partitioning is partitioned into equal subdomains centered at , , the scattering equations can be expressed in matrix form as follows:...

    [...]

Journal ArticleDOI
TL;DR: This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization, showing genetic-algorithm optimization to be suitable for optimizing a broad class of problems of interest to the electromagnetic community.
Abstract: This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization. Genetic-algorithm (GA) optimizers are robust, stochastic search methods modeled on the concepts of natural selection and evolution. The relationship between traditional optimization techniques and the GA is discussed. Step-by-step implementation aspects of the GA are detailed, through an example with the objective of providing useful guidelines for the potential user. Extensive use is made of sidebars and graphical presentation to facilitate understanding. The tutorial is followed by a discussion of several electromagnetic applications in which the GA has proven useful. The applications discussed include the design of lightweight, broadband microwave absorbers, the reduction of array sidelobes in thinned arrays, the design of shaped-beam antenna arrays, the extraction of natural resonance modes of radar targets from backscattered response data, and the design of broadband patch antennas. Genetic-algorithm optimization is shown to be suitable for optimizing a broad class of problems of interest to the electromagnetic community. A comprehensive list of key references, organized by application category, is also provided.

855 citations


"Effective exploitation of the a pri..." refers methods in this paper

  • ...of problem unknowns, the minimization of is carried out by means of a suitable version of a genetic algorithm [9], [10]....

    [...]

  • ...Concerning the optimization procedure, the following parametric setup has been assumed: , (mutation probability), (bit-mutation probability), and (crossover probability) [10]....

    [...]

Book
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753 citations

Book
01 Jan 2000
TL;DR: In this article, a detailed dielectric composite evaluation is presented, along with a surface crack detection approach for near-field measurement techniques and applications, and a survey of the current state of the art is presented.
Abstract: Foreword. 1. Introduction. 2. Microwave characterization. 3. Layered dielectric composite evaluation. 4. Surface crack detection. 5. Near-field measurement techniques and applications. 6. Other developments and future. Index.

338 citations


"Effective exploitation of the a pri..." refers background in this paper

  • ...However, testing an object for evaluating the presence of a defect allows us to reduce the computational complexity by fully exploiting the (generally) available a priori information concerning the unperturbed structure [1]....

    [...]

Trending Questions (1)
How to test a capacitor on a microwave?

This paper presents an innovative microwave technique, which is suitable for the detection of defects in nondestructive-test and nondestructive-evaluation (NDT/NDE) applications where a lot of a priori information is available.