1,721,006 research outputs found
ISSUES IN A RECONSTRUCTION ALGORITHM FOR THE DERT
No full textThe Electrical Resistive Tomography is a non-invasive diagnostic technique based on the identification of the conductivity inside a control volume from its response to low frequency currents. Possible improvements in ERT for clinical diagnostics achievable by exploiting devices with internal contact to the analysed tissues are presented in the paper
Effective Exploitation of Prior Information in Electrical Impedance Tomography for Thermal Monitoring of Hyperthermia Treatments
No full textReal-time monitoring of hyperthermia treatments for liver cancers by noninvasive techniques was investigated in the last two decades.
Among the proposed techniques, Electrical Impedance Tomography (EIT) arises particular interest for its low cost and sensitivity to
tissues parameter changes to be detected. In this paper, an approach based on the intensive but critical exploitation of prior information
is proposed and a preconditioning method of the impedance measurements based on a sensitivity analysis is assessed
An Effective Formulation of the Electrical Impedance Tomography Problem for Monitoring Clinical Treatments Effects
No full textImpact of Uncertainties in MagnetoEncephalography Inverse Problem
No full textMagneto encephalography is a technique, based on inverse problem approach, imaging human brain activity trough magnetic sources identification inside the skull from external magnetic measurements taken using SQUIDs. In this paper, the impact of the uncertainties affecting the reconstructed data caused by the measurement noise and uncertainties is discussed
Virtual Positioning and Shaping of Source Fields for ECT of Tubes
No full textPurpose – The purpose of this paper is to present a new approach to drive the excitation field sources in the eddy current testing (ECT) of tubular conductive structures.
Design/methodology/approach – The magnetic field used for ECT is generated by pairs of counter-series connected coils, driven by AC currents. The phase and amplitude of the currents is electronically controlled in order to shape the primary field map, allowing circumferential sweeps until the presence of defects is detected, and then “focusing” the field on the defective section of the tube, increasing in this way the sensibility of the ECT probes in the targeted area, in order to determine with higher precision, the position, and the shape of the defect.
Findings – If suitably designed, the field measurement system allows to enable/disable a number of probes to enhance the resolution in the defect area while keeping low the number of required data channels.
Research limitations/implications – The analyzed geometry is limited to circular-shaped tubes, of infinite extent. Future work should be on the extension of the methodology to general shapes, and to finite length cylinders.
Practical implications – The proposed method allows to enhance resolution in ECT of tubes at the end of production lines, guaranteeing a first, simple yet effective quality assessment of tubes in industrial environments.
Originality/value – The paper presents a new technique to test conductive tubes using fixed excitation system, but allowing to focus magnetic field in defective regions. The method could be helpful for industrial diagnostics
Effect of anisotropy in estimation of brain sources and conductivities via coupled EEG and MEG
No full textPurpose: This paper proposes an approach for the coupled EEG-MEG data analysis that takes into account the
anisotropy of brain tissues and the different sensitivities of EEG and MEG measurements.
Design/methodology/approach: The study is carried out by using a combination of analytical and numerical methods. In
particular, where available, closed solutions are used to evaluate the numerical errors, while FEM models are used where
anisotropy and geometrical characteristics make analytical solutions not applicable.
Findings: The impact of tissues anisotropy on coupled EEG-MEG analysis has been assessed, and the effectiveness of
an approach based on smart exploitation of different EEG and MEG sensitivity to improve sources reconstruction has been
demonstrated numerically.
Research limitations/implications: The analysis has been carried out using a spherical head model, and on simulated data.
Practical implications: The proposed approach allows to improve the localization of equivalent sources for the description
of cellular brain activity.
Originality/value: The properties of objective functions used in brain sources reconstruction from EEG and MEG has been
investigated taking into account tissues anisotropy in the spherical symmetric case. In addition a formulation of the joint source
and tissues tensor conductivity estimation by exploiting simultaneously bioelectric and biomagnetic measurements based on
the complementary sensitivity of those measurements has been presented
An Electrical Resistive Tomography Based on Direct Information
No full textAn approach to non destructive testing suitable for solving a class of particular inverse problems whose peculiarity is to have the defect electrically accessible is proposed. The impact of this feature on the mathematical formulation of the problem and the advantages in terms of improvement of the sensitivity of the measurement system are discussed through the evaluation of the shape and the dimension of the uncertainty band. An application oriented to the diagnostic for underground concrete structures is then presented
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