Small Scale Non-Invasive Imaging Using Magnetic Induction Tomography - Hardware Design

This study is conducted to preliminary image the conductivity profile through the development of small scale non-invasive Magnetic Induction Tomography (MIT) system.  It is proved that the Magnetic Induction Tomography interested in mapping the passive electrical properties of materials; conductivity (σ), permittivity (ε) and permeability (µ) in both process and medical tomography.  The system is realized by designing the functional ferrite-core coil sensors, electronic measurements circuits for excitation and receiving coil, data acquisition system for transferring the data to the PC and suitable image reconstruction algorithm for providing the conductivity distributions measurement. The important characteristic for excitation coil is the one that can maintain the stability the optimum sine wave frequency ranging from 400 kHz up to 10 MHz.  The sine waves are fed to the excitation coil through the application of high current amplifier component respectively. In the experiments, the copper phantom represent as high conductivity material were placed into the region of interest.  The initial 16 channel MIT consists of 8 excitation coil and 8 receiving coil stacked alternately.  On the receiving circuit, the major problem is the weak secondary signal perturbation sensed by the receiving coil has been improved by placing the variable amplifier on each receiver. The enhancement of conductivity profile imaging has been made by using a common Linear Back Projection (LBP) algorithm.  The measurement was done on single and dual arrangement of copper phantom aligns in random coordinate so that the sensitivity of the excitation and receiving coil sensor can be experimentally observed.  The imaging’s results show that the hardware’s and algorithm used was capable to process the data captured at the receiver.  The results obtained can be useful for further improvement and research towards magnetic induction tomography

A mathematical model and inversion procedure for Magneto-Acousto-Electric Tomography (MAET)

Magneto-Acousto-Electric Tomography (MAET), also known as the Lorentz force or Hall effect tomography, is a novel hybrid modality designed to be a high-resolution alternative to the unstable Electrical Impedance Tomography. In the present paper we analyze existing mathematical models of this method, and propose a general procedure for solving the inverse problem associated with MAET. It consists in applying to the data one of the algorithms of Thermo-Acoustic tomography, followed by solving the Neumann problem for the Laplace equation and the Poisson equation. For the particular case when the region of interest is a cube, we present an explicit series solution resulting in a fast reconstruction algorithm. As we show, both analytically and numerically, MAET is a stable technique yilelding high-resolution images even in the presence of significant noise in the data

OKREŚLENIE OPTYMALNEGO KROKU SKANOWANIA DO OCENY JAKOŚCI REKONSTRUKCJI OBRAZU W TOMOGRAFII MAGNETOAKUSTYCZNEJ ZE WZBUDZENIEM INDUKCYJNYM

Magnetoacoustic Tomography with Magnetic Induction (MAT-MI) is a new hybrid imaging modality especially dedicated for non-invasive electrical conductivity imaging of low-conductivity objects such as e.g. biological tissues. The purpose of the present paper is to determine the optimal scanning step assuring the best quality of image reconstruction. In order to resolve this problem a special image reconstruction quality indicator based on binarization has been applied. Taking into account different numbers of measuring points and various image processing algorithms, the conditions allowing successful image reconstruction have been provided in the paper. Finally, the image reconstruction examples for objects’ complex shapes have been analyzed.Tomografia magnetoakustyczna ze wzbudzeniem indukcyjnym (MAT-MI) to nowa hybrydowa technika obrazowania dedykowana szczególnie do nieinwazyjnego obrazowania obiektów o niskiej konduktywności elektrycznej, takich jak na przykład tkanki biologiczne. Celem niniejszej pracy jest określenie optymalnego kroku skanowania zapewniającego najlepszą jakość rekonstrukcji obrazu. W celu rozwiązania tego problemu zastosowano specjalny wskaźnik jakości rekonstrukcji obrazu bazujący na binaryzacji. W artykule przedstawiono warunki umożliwiające pomyślne zrekonstruowanie obrazu biorąc pod uwagę różną liczbę punktów pomiarowych oraz różne algorytmy przetwarzania obrazu. W końcowym etapie pracy przeanalizowano przykłady rekonstrukcji obrazu dla obiektów o bardziej złożonych kształtach

Pavement testing by integrated geophysical methods: Feasibility, resolution and diagnostic potential

This work is focused on the assessment of the diagnostic potential of several geophysical methods when applied to the investigation of a rigid airport pavement. The potential and limit of each technique are evaluated as well as the added value deriving from their integration. Firstly, we reconstruct a high-resolution image of the pavement by a large electromagnetic and georadar screening. An advanced processing of georadar data, implemented through the picking of the arrival times of reflections for each profile, provides a quantitative estimation of the deviation between the design and the as-built thickness of layers. Additionally, electrical tomography has been applied to unequivocally identify the anomalous zones, where higher values of resistivity would be associated to porous zones that are prone to degradation and failure. The seismic tomographic survey had the additional purpose to recover the mechanical properties of the pavement in terms of both P- and S-waves and consequently of elastic constants (Poisson's ratio), whose values were consistent with those recovered in literature. The anomalies detected by each technique are consistent in their indications and they can be correlated to failure phenomena occurring at layer interfaces within the pavement structure or to unexpected variations of the layer thicknesses. The cost-effective geophysical campaign has validated the four-layered system deduced from the original design and has been used to reconstruct a high-resolution map of the pavement in order to discriminate fractures, crack-prone areas or areas where the as-built differs from the original design

Image Reconstruction for Multi-frequency Electromagnetic Tomography based on Multiple Measurement Vector Model

Imaging the bio-impedance distribution of a biological sample can provide understandings about the sample's electrical properties which is an important indicator of physiological status. This paper presents a multi-frequency electromagnetic tomography (mfEMT) technique for biomedical imaging. The system consists of 8 channels of gradiometer coils with adjustable sensitivity and excitation frequency. To exploit the frequency correlation among each measurement, we reconstruct multiple frequency data simultaneously based on the Multiple Measurement Vector (MMV) model. The MMV problem is solved by using a sparse Bayesian learning method that is especially effective for sparse distribution. Both simulations and experiments have been conducted to verify the performance of the method. Results show that by taking advantage of multiple measurements, the proposed method is more robust to noisy data for ill-posed problems compared to the commonly used single measurement vector model.Comment: This is an accepted paper which has been submitted to I2MTC 2020 on Nov. 201